Merge branch 'for-3.17/drivers' of git://git.kernel.dk/linux-block

Pull block driver changes from Jens Axboe:
 "Nothing out of the ordinary here, this pull request contains:

   - A big round of fixes for bcache from Kent Overstreet, Slava Pestov,
     and Surbhi Palande.  No new features, just a lot of fixes.

   - The usual round of drbd updates from Andreas Gruenbacher, Lars
     Ellenberg, and Philipp Reisner.

   - virtio_blk was converted to blk-mq back in 3.13, but now Ming Lei
     has taken it one step further and added support for actually using
     more than one queue.

   - Addition of an explicit SG_FLAG_Q_AT_HEAD for block/bsg, to
     compliment the the default behavior of adding to the tail of the
     queue.  From Douglas Gilbert"

* 'for-3.17/drivers' of git://git.kernel.dk/linux-block: (86 commits)
  bcache: Drop unneeded blk_sync_queue() calls
  bcache: add mutex lock for bch_is_open
  bcache: Correct printing of btree_gc_max_duration_ms
  bcache: try to set b->parent properly
  bcache: fix memory corruption in init error path
  bcache: fix crash with incomplete cache set
  bcache: Fix more early shutdown bugs
  bcache: fix use-after-free in btree_gc_coalesce()
  bcache: Fix an infinite loop in journal replay
  bcache: fix crash in bcache_btree_node_alloc_fail tracepoint
  bcache: bcache_write tracepoint was crashing
  bcache: fix typo in bch_bkey_equal_header
  bcache: Allocate bounce buffers with GFP_NOWAIT
  bcache: Make sure to pass GFP_WAIT to mempool_alloc()
  bcache: fix uninterruptible sleep in writeback thread
  bcache: wait for buckets when allocating new btree root
  bcache: fix crash on shutdown in passthrough mode
  bcache: fix lockdep warnings on shutdown
  bcache allocator: send discards with correct size
  bcache: Fix to remove the rcu_sched stalls.
  ...

16 files changed, 2758 insertions, 1218 deletions

diff --git a/drivers/block/drbd/Makefile b/drivers/block/drbd/Makefile
index 8b450338075e..4464e353c1e8 100644
--- a/drivers/block/drbd/Makefile
+++ b/drivers/block/drbd/Makefile
@@ -3,5 +3,6 @@ drbd-y += drbd_worker.o drbd_receiver.o drbd_req.o drbd_actlog.o
 drbd-y += drbd_main.o drbd_strings.o drbd_nl.o
 drbd-y += drbd_interval.o drbd_state.o
 drbd-y += drbd_nla.o
+drbd-$(CONFIG_DEBUG_FS) += drbd_debugfs.o
 
 obj-$(CONFIG_BLK_DEV_DRBD)     += drbd.o
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 05a1780ffa85..d26a3fa63688 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -92,34 +92,26 @@ struct __packed al_transaction_on_disk {
         __be32  context[AL_CONTEXT_PER_TRANSACTION];
 };
 
-struct update_odbm_work {
-        struct drbd_work w;
-        struct drbd_device *device;
-        unsigned int enr;
-};
-
-struct update_al_work {
-        struct drbd_work w;
-        struct drbd_device *device;
-        struct completion event;
-        int err;
-};
-
-
-void *drbd_md_get_buffer(struct drbd_device *device)
+void *drbd_md_get_buffer(struct drbd_device *device, const char *intent)
 {
         int r;
 
         wait_event(device->misc_wait,
-                   (r = atomic_cmpxchg(&device->md_io_in_use, 0, 1)) == 0 ||
+                   (r = atomic_cmpxchg(&device->md_io.in_use, 0, 1)) == 0 ||
                    device->state.disk <= D_FAILED);
 
-        return r ? NULL : page_address(device->md_io_page);
+        if (r)
+                return NULL;
+
+        device->md_io.current_use = intent;
+        device->md_io.start_jif = jiffies;
+        device->md_io.submit_jif = device->md_io.start_jif - 1;
+        return page_address(device->md_io.page);
 }
 
 void drbd_md_put_buffer(struct drbd_device *device)
 {
-        if (atomic_dec_and_test(&device->md_io_in_use))
+        if (atomic_dec_and_test(&device->md_io.in_use))
                 wake_up(&device->misc_wait);
 }
 
@@ -145,10 +137,11 @@ void wait_until_done_or_force_detached(struct drbd_device *device, struct drbd_b
 
 static int _drbd_md_sync_page_io(struct drbd_device *device,
                                  struct drbd_backing_dev *bdev,
-                                 struct page *page, sector_t sector,
-                                 int rw, int size)
+                                 sector_t sector, int rw)
 {
         struct bio *bio;
+        /* we do all our meta data IO in aligned 4k blocks. */
+        const int size = 4096;
         int err;
 
         device->md_io.done = 0;
@@ -156,15 +149,15 @@ static int _drbd_md_sync_page_io(struct drbd_device *device,
 
         if ((rw & WRITE) && !test_bit(MD_NO_FUA, &device->flags))
                 rw |= REQ_FUA | REQ_FLUSH;
-        rw |= REQ_SYNC;
+        rw |= REQ_SYNC | REQ_NOIDLE;
 
         bio = bio_alloc_drbd(GFP_NOIO);
         bio->bi_bdev = bdev->md_bdev;
         bio->bi_iter.bi_sector = sector;
         err = -EIO;
-        if (bio_add_page(bio, page, size, 0) != size)
+        if (bio_add_page(bio, device->md_io.page, size, 0) != size)
                 goto out;
-        bio->bi_private = &device->md_io;
+        bio->bi_private = device;
         bio->bi_end_io = drbd_md_io_complete;
         bio->bi_rw = rw;
 
@@ -179,7 +172,8 @@ static int _drbd_md_sync_page_io(struct drbd_device *device,
         }
 
         bio_get(bio); /* one bio_put() is in the completion handler */
-        atomic_inc(&device->md_io_in_use); /* drbd_md_put_buffer() is in the completion handler */
+        atomic_inc(&device->md_io.in_use); /* drbd_md_put_buffer() is in the completion handler */
+        device->md_io.submit_jif = jiffies;
         if (drbd_insert_fault(device, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
                 bio_endio(bio, -EIO);
         else
@@ -197,9 +191,7 @@ int drbd_md_sync_page_io(struct drbd_device *device, struct drbd_backing_dev *bd
                          sector_t sector, int rw)
 {
         int err;
-        struct page *iop = device->md_io_page;
-
-        D_ASSERT(device, atomic_read(&device->md_io_in_use) == 1);
+        D_ASSERT(device, atomic_read(&device->md_io.in_use) == 1);
 
         BUG_ON(!bdev->md_bdev);
 
@@ -214,8 +206,7 @@ int drbd_md_sync_page_io(struct drbd_device *device, struct drbd_backing_dev *bd
                      current->comm, current->pid, __func__,
                      (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
 
-        /* we do all our meta data IO in aligned 4k blocks. */
-        err = _drbd_md_sync_page_io(device, bdev, iop, sector, rw, 4096);
+        err = _drbd_md_sync_page_io(device, bdev, sector, rw);
         if (err) {
                 drbd_err(device, "drbd_md_sync_page_io(,%llus,%s) failed with error %d\n",
                     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ", err);
@@ -297,26 +288,12 @@ bool drbd_al_begin_io_prepare(struct drbd_device *device, struct drbd_interval *
         return need_transaction;
 }
 
-static int al_write_transaction(struct drbd_device *device, bool delegate);
-
-/* When called through generic_make_request(), we must delegate
- * activity log I/O to the worker thread: a further request
- * submitted via generic_make_request() within the same task
- * would be queued on current->bio_list, and would only start
- * after this function returns (see generic_make_request()).
- *
- * However, if we *are* the worker, we must not delegate to ourselves.
- */
+static int al_write_transaction(struct drbd_device *device);
 
-/*
- * @delegate:   delegate activity log I/O to the worker thread
- */
-void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate)
+void drbd_al_begin_io_commit(struct drbd_device *device)
 {
         bool locked = false;
 
-        BUG_ON(delegate && current == first_peer_device(device)->connection->worker.task);
-
         /* Serialize multiple transactions.
          * This uses test_and_set_bit, memory barrier is implicit.
          */
@@ -335,7 +312,7 @@ void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate)
                         rcu_read_unlock();
 
                         if (write_al_updates)
-                                al_write_transaction(device, delegate);
+                                al_write_transaction(device);
                         spin_lock_irq(&device->al_lock);
                         /* FIXME
                         if (err)
@@ -352,12 +329,10 @@ void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate)
 /*
  * @delegate:   delegate activity log I/O to the worker thread
  */
-void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i, bool delegate)
+void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i)
 {
-        BUG_ON(delegate && current == first_peer_device(device)->connection->worker.task);
-
         if (drbd_al_begin_io_prepare(device, i))
-                drbd_al_begin_io_commit(device, delegate);
+                drbd_al_begin_io_commit(device);
 }
 
 int drbd_al_begin_io_nonblock(struct drbd_device *device, struct drbd_interval *i)
@@ -380,8 +355,19 @@ int drbd_al_begin_io_nonblock(struct drbd_device *device, struct drbd_interval *
         /* We want all necessary updates for a given request within the same transaction
          * We could first check how many updates are *actually* needed,
          * and use that instead of the worst-case nr_al_extents */
-        if (available_update_slots < nr_al_extents)
-                return -EWOULDBLOCK;
+        if (available_update_slots < nr_al_extents) {
+                /* Too many activity log extents are currently "hot".
+                 *
+                 * If we have accumulated pending changes already,
+                 * we made progress.
+                 *
+                 * If we cannot get even a single pending change through,
+                 * stop the fast path until we made some progress,
+                 * or requests to "cold" extents could be starved. */
+                if (!al->pending_changes)
+                        __set_bit(__LC_STARVING, &device->act_log->flags);
+                return -ENOBUFS;
+        }
 
         /* Is resync active in this area? */
         for (enr = first; enr <= last; enr++) {
@@ -452,15 +438,6 @@ static unsigned int al_extent_to_bm_page(unsigned int al_enr)
                  (AL_EXTENT_SHIFT - BM_BLOCK_SHIFT));
 }
 
-static unsigned int rs_extent_to_bm_page(unsigned int rs_enr)
-{
-        return rs_enr >>
-                /* bit to page */
-                ((PAGE_SHIFT + 3) -
-                /* resync extent number to bit */
-                 (BM_EXT_SHIFT - BM_BLOCK_SHIFT));
-}
-
 static sector_t al_tr_number_to_on_disk_sector(struct drbd_device *device)
 {
         const unsigned int stripes = device->ldev->md.al_stripes;
@@ -479,8 +456,7 @@ static sector_t al_tr_number_to_on_disk_sector(struct drbd_device *device)
         return device->ldev->md.md_offset + device->ldev->md.al_offset + t;
 }
 
-static int
-_al_write_transaction(struct drbd_device *device)
+int al_write_transaction(struct drbd_device *device)
 {
         struct al_transaction_on_disk *buffer;
         struct lc_element *e;
@@ -505,7 +481,8 @@ _al_write_transaction(struct drbd_device *device)
                 return -EIO;
         }
 
-        buffer = drbd_md_get_buffer(device); /* protects md_io_buffer, al_tr_cycle, ... */
+        /* protects md_io_buffer, al_tr_cycle, ... */
+        buffer = drbd_md_get_buffer(device, __func__);
         if (!buffer) {
                 drbd_err(device, "disk failed while waiting for md_io buffer\n");
                 put_ldev(device);
@@ -590,38 +567,6 @@ _al_write_transaction(struct drbd_device *device)
         return err;
 }
 
-
-static int w_al_write_transaction(struct drbd_work *w, int unused)
-{
-        struct update_al_work *aw = container_of(w, struct update_al_work, w);
-        struct drbd_device *device = aw->device;
-        int err;
-
-        err = _al_write_transaction(device);
-        aw->err = err;
-        complete(&aw->event);
-
-        return err != -EIO ? err : 0;
-}
-
-/* Calls from worker context (see w_restart_disk_io()) need to write the
-   transaction directly. Others came through generic_make_request(),
-   those need to delegate it to the worker. */
-static int al_write_transaction(struct drbd_device *device, bool delegate)
-{
-        if (delegate) {
-                struct update_al_work al_work;
-                init_completion(&al_work.event);
-                al_work.w.cb = w_al_write_transaction;
-                al_work.device = device;
-                drbd_queue_work_front(&first_peer_device(device)->connection->sender_work,
-                                      &al_work.w);
-                wait_for_completion(&al_work.event);
-                return al_work.err;
-        } else
-                return _al_write_transaction(device);
-}
-
 static int _try_lc_del(struct drbd_device *device, struct lc_element *al_ext)
 {
         int rv;
@@ -682,72 +627,56 @@ int drbd_initialize_al(struct drbd_device *device, void *buffer)
         return 0;
 }
 
-static int w_update_odbm(struct drbd_work *w, int unused)
-{
-        struct update_odbm_work *udw = container_of(w, struct update_odbm_work, w);
-        struct drbd_device *device = udw->device;
-        struct sib_info sib = { .sib_reason = SIB_SYNC_PROGRESS, };
-
-        if (!get_ldev(device)) {
-                if (__ratelimit(&drbd_ratelimit_state))
-                        drbd_warn(device, "Can not update on disk bitmap, local IO disabled.\n");
-                kfree(udw);
-                return 0;
-        }
-
-        drbd_bm_write_page(device, rs_extent_to_bm_page(udw->enr));
-        put_ldev(device);
-
-        kfree(udw);
-
-        if (drbd_bm_total_weight(device) <= device->rs_failed) {
-                switch (device->state.conn) {
-                case C_SYNC_SOURCE:  case C_SYNC_TARGET:
-                case C_PAUSED_SYNC_S: case C_PAUSED_SYNC_T:
-                        drbd_resync_finished(device);
-                default:
-                        /* nothing to do */
-                        break;
-                }
-        }
-        drbd_bcast_event(device, &sib);
-
-        return 0;
-}
-
+static const char *drbd_change_sync_fname[] = {
+        [RECORD_RS_FAILED] = "drbd_rs_failed_io",
+        [SET_IN_SYNC] = "drbd_set_in_sync",
+        [SET_OUT_OF_SYNC] = "drbd_set_out_of_sync"
+};
 
 /* ATTENTION. The AL's extents are 4MB each, while the extents in the
  * resync LRU-cache are 16MB each.
  * The caller of this function has to hold an get_ldev() reference.
  *
+ * Adjusts the caching members ->rs_left (success) or ->rs_failed (!success),
+ * potentially pulling in (and recounting the corresponding bits)
+ * this resync extent into the resync extent lru cache.
+ *
+ * Returns whether all bits have been cleared for this resync extent,
+ * precisely: (rs_left <= rs_failed)
+ *
  * TODO will be obsoleted once we have a caching lru of the on disk bitmap
  */
-static void drbd_try_clear_on_disk_bm(struct drbd_device *device, sector_t sector,
-                                      int count, int success)
+static bool update_rs_extent(struct drbd_device *device,
+                unsigned int enr, int count,
+                enum update_sync_bits_mode mode)
 {
         struct lc_element *e;
-        struct update_odbm_work *udw;
-
-        unsigned int enr;
 
         D_ASSERT(device, atomic_read(&device->local_cnt));
 
-        /* I simply assume that a sector/size pair never crosses
-         * a 16 MB extent border. (Currently this is true...) */
-        enr = BM_SECT_TO_EXT(sector);
-
-        e = lc_get(device->resync, enr);
+        /* When setting out-of-sync bits,
+         * we don't need it cached (lc_find).
+         * But if it is present in the cache,
+         * we should update the cached bit count.
+         * Otherwise, that extent should be in the resync extent lru cache
+         * already -- or we want to pull it in if necessary -- (lc_get),
+         * then update and check rs_left and rs_failed. */
+        if (mode == SET_OUT_OF_SYNC)
+                e = lc_find(device->resync, enr);
+        else
+                e = lc_get(device->resync, enr);
         if (e) {
                 struct bm_extent *ext = lc_entry(e, struct bm_extent, lce);
                 if (ext->lce.lc_number == enr) {
-                        if (success)
+                        if (mode == SET_IN_SYNC)
                                 ext->rs_left -= count;
+                        else if (mode == SET_OUT_OF_SYNC)
+                                ext->rs_left += count;
                         else
                                 ext->rs_failed += count;
                         if (ext->rs_left < ext->rs_failed) {
-                                drbd_warn(device, "BAD! sector=%llus enr=%u rs_left=%d "
+                                drbd_warn(device, "BAD! enr=%u rs_left=%d "
                                     "rs_failed=%d count=%d cstate=%s\n",
-                                     (unsigned long long)sector,
                                      ext->lce.lc_number, ext->rs_left,
                                      ext->rs_failed, count,
                                      drbd_conn_str(device->state.conn));
@@ -781,34 +710,27 @@ static void drbd_try_clear_on_disk_bm(struct drbd_device *device, sector_t secto
                                      ext->lce.lc_number, ext->rs_failed);
                         }
                         ext->rs_left = rs_left;
-                        ext->rs_failed = success ? 0 : count;
+                        ext->rs_failed = (mode == RECORD_RS_FAILED) ? count : 0;
                         /* we don't keep a persistent log of the resync lru,
                          * we can commit any change right away. */
                         lc_committed(device->resync);
                 }
-                lc_put(device->resync, &ext->lce);
+                if (mode != SET_OUT_OF_SYNC)
+                        lc_put(device->resync, &ext->lce);
                 /* no race, we are within the al_lock! */
 
-                if (ext->rs_left == ext->rs_failed) {
+                if (ext->rs_left <= ext->rs_failed) {
                         ext->rs_failed = 0;
-
-                        udw = kmalloc(sizeof(*udw), GFP_ATOMIC);
-                        if (udw) {
-                                udw->enr = ext->lce.lc_number;
-                                udw->w.cb = w_update_odbm;
-                                udw->device = device;
-                                drbd_queue_work_front(&first_peer_device(device)->connection->sender_work,
-                                                      &udw->w);
-                        } else {
-                                drbd_warn(device, "Could not kmalloc an udw\n");
-                        }
+                        return true;
                 }
-        } else {
+        } else if (mode != SET_OUT_OF_SYNC) {
+                /* be quiet if lc_find() did not find it. */
                 drbd_err(device, "lc_get() failed! locked=%d/%d flags=%lu\n",
                     device->resync_locked,
                     device->resync->nr_elements,
                     device->resync->flags);
         }
+        return false;
 }
 
 void drbd_advance_rs_marks(struct drbd_device *device, unsigned long still_to_go)
@@ -827,105 +749,105 @@ void drbd_advance_rs_marks(struct drbd_device *device, unsigned long still_to_go
         }
 }
 
-/* clear the bit corresponding to the piece of storage in question:
- * size byte of data starting from sector.  Only clear a bits of the affected
- * one ore more _aligned_ BM_BLOCK_SIZE blocks.
- *
- * called by worker on C_SYNC_TARGET and receiver on SyncSource.
- *
- */
-void __drbd_set_in_sync(struct drbd_device *device, sector_t sector, int size,
-                       const char *file, const unsigned int line)
+/* It is called lazy update, so don't do write-out too often. */
+static bool lazy_bitmap_update_due(struct drbd_device *device)
 {
-        /* Is called from worker and receiver context _only_ */
-        unsigned long sbnr, ebnr, lbnr;
-        unsigned long count = 0;
-        sector_t esector, nr_sectors;
-        int wake_up = 0;
-        unsigned long flags;
+        return time_after(jiffies, device->rs_last_bcast + 2*HZ);
+}
 
-        if (size <= 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_DISCARD_SIZE) {
-                drbd_err(device, "drbd_set_in_sync: sector=%llus size=%d nonsense!\n",
-                                (unsigned long long)sector, size);
+static void maybe_schedule_on_disk_bitmap_update(struct drbd_device *device, bool rs_done)
+{
+        if (rs_done)
+                set_bit(RS_DONE, &device->flags);
+                /* and also set RS_PROGRESS below */
+        else if (!lazy_bitmap_update_due(device))
                 return;
-        }
-
-        if (!get_ldev(device))
-                return; /* no disk, no metadata, no bitmap to clear bits in */
-
-        nr_sectors = drbd_get_capacity(device->this_bdev);
-        esector = sector + (size >> 9) - 1;
-
-        if (!expect(sector < nr_sectors))
-                goto out;
-        if (!expect(esector < nr_sectors))
-                esector = nr_sectors - 1;
-
-        lbnr = BM_SECT_TO_BIT(nr_sectors-1);
-
-        /* we clear it (in sync).
-         * round up start sector, round down end sector.  we make sure we only
-         * clear full, aligned, BM_BLOCK_SIZE (4K) blocks */
-        if (unlikely(esector < BM_SECT_PER_BIT-1))
-                goto out;
-        if (unlikely(esector == (nr_sectors-1)))
-                ebnr = lbnr;
-        else
-                ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
-        sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
 
-        if (sbnr > ebnr)
-                goto out;
+        drbd_device_post_work(device, RS_PROGRESS);
+}
 
+static int update_sync_bits(struct drbd_device *device,
+                unsigned long sbnr, unsigned long ebnr,
+                enum update_sync_bits_mode mode)
+{
         /*
-         * ok, (capacity & 7) != 0 sometimes, but who cares...
-         * we count rs_{total,left} in bits, not sectors.
+         * We keep a count of set bits per resync-extent in the ->rs_left
+         * caching member, so we need to loop and work within the resync extent
+         * alignment. Typically this loop will execute exactly once.
          */
-        count = drbd_bm_clear_bits(device, sbnr, ebnr);
-        if (count) {
-                drbd_advance_rs_marks(device, drbd_bm_total_weight(device));
-                spin_lock_irqsave(&device->al_lock, flags);
-                drbd_try_clear_on_disk_bm(device, sector, count, true);
-                spin_unlock_irqrestore(&device->al_lock, flags);
-
-                /* just wake_up unconditional now, various lc_chaged(),
-                 * lc_put() in drbd_try_clear_on_disk_bm(). */
-                wake_up = 1;
+        unsigned long flags;
+        unsigned long count = 0;
+        unsigned int cleared = 0;
+        while (sbnr <= ebnr) {
+                /* set temporary boundary bit number to last bit number within
+                 * the resync extent of the current start bit number,
+                 * but cap at provided end bit number */
+                unsigned long tbnr = min(ebnr, sbnr | BM_BLOCKS_PER_BM_EXT_MASK);
+                unsigned long c;
+
+                if (mode == RECORD_RS_FAILED)
+                        /* Only called from drbd_rs_failed_io(), bits
+                         * supposedly still set.  Recount, maybe some
+                         * of the bits have been successfully cleared
+                         * by application IO meanwhile.
+                         */
+                        c = drbd_bm_count_bits(device, sbnr, tbnr);
+                else if (mode == SET_IN_SYNC)
+                        c = drbd_bm_clear_bits(device, sbnr, tbnr);
+                else /* if (mode == SET_OUT_OF_SYNC) */
+                        c = drbd_bm_set_bits(device, sbnr, tbnr);
+
+                if (c) {
+                        spin_lock_irqsave(&device->al_lock, flags);
+                        cleared += update_rs_extent(device, BM_BIT_TO_EXT(sbnr), c, mode);
+                        spin_unlock_irqrestore(&device->al_lock, flags);
+                        count += c;
+                }
+                sbnr = tbnr + 1;
         }
-out:
-        put_ldev(device);
-        if (wake_up)
+        if (count) {
+                if (mode == SET_IN_SYNC) {
+                        unsigned long still_to_go = drbd_bm_total_weight(device);
+                        bool rs_is_done = (still_to_go <= device->rs_failed);
+                        drbd_advance_rs_marks(device, still_to_go);
+                        if (cleared || rs_is_done)
+                                maybe_schedule_on_disk_bitmap_update(device, rs_is_done);
+                } else if (mode == RECORD_RS_FAILED)
+                        device->rs_failed += count;
                 wake_up(&device->al_wait);
+        }
+        return count;
 }
 
-/*
- * this is intended to set one request worth of data out of sync.
- * affects at least 1 bit,
- * and at most 1+DRBD_MAX_BIO_SIZE/BM_BLOCK_SIZE bits.
+/* clear the bit corresponding to the piece of storage in question:
+ * size byte of data starting from sector.  Only clear a bits of the affected
+ * one ore more _aligned_ BM_BLOCK_SIZE blocks.
+ *
+ * called by worker on C_SYNC_TARGET and receiver on SyncSource.
  *
- * called by tl_clear and drbd_send_dblock (==drbd_make_request).
- * so this can be _any_ process.
  */
-int __drbd_set_out_of_sync(struct drbd_device *device, sector_t sector, int size,
-                            const char *file, const unsigned int line)
+int __drbd_change_sync(struct drbd_device *device, sector_t sector, int size,
+                enum update_sync_bits_mode mode,
+                const char *file, const unsigned int line)
 {
-        unsigned long sbnr, ebnr, flags;
+        /* Is called from worker and receiver context _only_ */
+        unsigned long sbnr, ebnr, lbnr;
+        unsigned long count = 0;
         sector_t esector, nr_sectors;
-        unsigned int enr, count = 0;
-        struct lc_element *e;
 
-        /* this should be an empty REQ_FLUSH */
-        if (size == 0)
+        /* This would be an empty REQ_FLUSH, be silent. */
+        if ((mode == SET_OUT_OF_SYNC) && size == 0)
                 return 0;
 
-        if (size < 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_DISCARD_SIZE) {
-                drbd_err(device, "sector: %llus, size: %d\n",
-                        (unsigned long long)sector, size);
+        if (size <= 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_DISCARD_SIZE) {
+                drbd_err(device, "%s: sector=%llus size=%d nonsense!\n",
+                                drbd_change_sync_fname[mode],
+                                (unsigned long long)sector, size);
                 return 0;
         }
 
         if (!get_ldev(device))
-                return 0; /* no disk, no metadata, no bitmap to set bits in */
+                return 0; /* no disk, no metadata, no bitmap to manipulate bits in */
 
         nr_sectors = drbd_get_capacity(device->this_bdev);
         esector = sector + (size >> 9) - 1;
@@ -935,25 +857,28 @@ int __drbd_set_out_of_sync(struct drbd_device *device, sector_t sector, int size
         if (!expect(esector < nr_sectors))
                 esector = nr_sectors - 1;
 
-        /* we set it out of sync,
-         * we do not need to round anything here */
-        sbnr = BM_SECT_TO_BIT(sector);
-        ebnr = BM_SECT_TO_BIT(esector);
-
-        /* ok, (capacity & 7) != 0 sometimes, but who cares...
-         * we count rs_{total,left} in bits, not sectors.  */
-        spin_lock_irqsave(&device->al_lock, flags);
-        count = drbd_bm_set_bits(device, sbnr, ebnr);
+        lbnr = BM_SECT_TO_BIT(nr_sectors-1);
 
-        enr = BM_SECT_TO_EXT(sector);
-        e = lc_find(device->resync, enr);
-        if (e)
-                lc_entry(e, struct bm_extent, lce)->rs_left += count;
-        spin_unlock_irqrestore(&device->al_lock, flags);
+        if (mode == SET_IN_SYNC) {
+                /* Round up start sector, round down end sector.  We make sure
+                 * we only clear full, aligned, BM_BLOCK_SIZE blocks. */
+                if (unlikely(esector < BM_SECT_PER_BIT-1))
+                        goto out;
+                if (unlikely(esector == (nr_sectors-1)))
+                        ebnr = lbnr;
+                else
+                        ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
+                sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
+        } else {
+                /* We set it out of sync, or record resync failure.
+                 * Should not round anything here. */
+                sbnr = BM_SECT_TO_BIT(sector);
+                ebnr = BM_SECT_TO_BIT(esector);
+        }
 
+        count = update_sync_bits(device, sbnr, ebnr, mode);
 out:
         put_ldev(device);
-
         return count;
 }
 
@@ -1075,6 +1000,15 @@ int drbd_try_rs_begin_io(struct drbd_device *device, sector_t sector)
         struct lc_element *e;
         struct bm_extent *bm_ext;
         int i;
+        bool throttle = drbd_rs_should_slow_down(device, sector, true);
+
+        /* If we need to throttle, a half-locked (only marked BME_NO_WRITES,
+         * not yet BME_LOCKED) extent needs to be kicked out explicitly if we
+         * need to throttle. There is at most one such half-locked extent,
+         * which is remembered in resync_wenr. */
+
+        if (throttle && device->resync_wenr != enr)
+                return -EAGAIN;
 
         spin_lock_irq(&device->al_lock);
         if (device->resync_wenr != LC_FREE && device->resync_wenr != enr) {
@@ -1098,8 +1032,10 @@ int drbd_try_rs_begin_io(struct drbd_device *device, sector_t sector)
                         D_ASSERT(device, test_bit(BME_NO_WRITES, &bm_ext->flags));
                         clear_bit(BME_NO_WRITES, &bm_ext->flags);
                         device->resync_wenr = LC_FREE;
-                        if (lc_put(device->resync, &bm_ext->lce) == 0)
+                        if (lc_put(device->resync, &bm_ext->lce) == 0) {
+                                bm_ext->flags = 0;
                                 device->resync_locked--;
+                        }
                         wake_up(&device->al_wait);
                 } else {
                         drbd_alert(device, "LOGIC BUG\n");
@@ -1161,8 +1097,20 @@ proceed:
         return 0;
 
 try_again:
-        if (bm_ext)
-                device->resync_wenr = enr;
+        if (bm_ext) {
+                if (throttle) {
+                        D_ASSERT(device, !test_bit(BME_LOCKED, &bm_ext->flags));
+                        D_ASSERT(device, test_bit(BME_NO_WRITES, &bm_ext->flags));
+                        clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                        device->resync_wenr = LC_FREE;
+                        if (lc_put(device->resync, &bm_ext->lce) == 0) {
+                                bm_ext->flags = 0;
+                                device->resync_locked--;
+                        }
+                        wake_up(&device->al_wait);
+                } else
+                        device->resync_wenr = enr;
+        }
         spin_unlock_irq(&device->al_lock);
         return -EAGAIN;
 }
@@ -1270,69 +1218,3 @@ int drbd_rs_del_all(struct drbd_device *device)
 
         return 0;
 }
-
-/**
- * drbd_rs_failed_io() - Record information on a failure to resync the specified blocks
- * @device:     DRBD device.
- * @sector:     The sector number.
- * @size:       Size of failed IO operation, in byte.
- */
-void drbd_rs_failed_io(struct drbd_device *device, sector_t sector, int size)
-{
-        /* Is called from worker and receiver context _only_ */
-        unsigned long sbnr, ebnr, lbnr;
-        unsigned long count;
-        sector_t esector, nr_sectors;
-        int wake_up = 0;
-
-        if (size <= 0 || !IS_ALIGNED(size, 512) || size > DRBD_MAX_DISCARD_SIZE) {
-                drbd_err(device, "drbd_rs_failed_io: sector=%llus size=%d nonsense!\n",
-                                (unsigned long long)sector, size);
-                return;
-        }
-        nr_sectors = drbd_get_capacity(device->this_bdev);
-        esector = sector + (size >> 9) - 1;
-
-        if (!expect(sector < nr_sectors))
-                return;
-        if (!expect(esector < nr_sectors))
-                esector = nr_sectors - 1;
-
-        lbnr = BM_SECT_TO_BIT(nr_sectors-1);
-
-        /*
-         * round up start sector, round down end sector.  we make sure we only
-         * handle full, aligned, BM_BLOCK_SIZE (4K) blocks */
-        if (unlikely(esector < BM_SECT_PER_BIT-1))
-                return;
-        if (unlikely(esector == (nr_sectors-1)))
-                ebnr = lbnr;
-        else
-                ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
-        sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
-
-        if (sbnr > ebnr)
-                return;
-
-        /*
-         * ok, (capacity & 7) != 0 sometimes, but who cares...
-         * we count rs_{total,left} in bits, not sectors.
-         */
-        spin_lock_irq(&device->al_lock);
-        count = drbd_bm_count_bits(device, sbnr, ebnr);
-        if (count) {
-                device->rs_failed += count;
-
-                if (get_ldev(device)) {
-                        drbd_try_clear_on_disk_bm(device, sector, count, false);
-                        put_ldev(device);
-                }
-
-                /* just wake_up unconditional now, various lc_chaged(),
-                 * lc_put() in drbd_try_clear_on_disk_bm(). */
-                wake_up = 1;
-        }
-        spin_unlock_irq(&device->al_lock);
-        if (wake_up)
-                wake_up(&device->al_wait);
-}
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 1aa29f8fdfe1..426c97aef900 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -22,6 +22,8 @@
    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
+
 #include <linux/bitops.h>
 #include <linux/vmalloc.h>
 #include <linux/string.h>
@@ -353,9 +355,8 @@ static void bm_free_pages(struct page **pages, unsigned long number)
 
         for (i = 0; i < number; i++) {
                 if (!pages[i]) {
-                        printk(KERN_ALERT "drbd: bm_free_pages tried to free "
-                                          "a NULL pointer; i=%lu n=%lu\n",
-                                          i, number);
+                        pr_alert("bm_free_pages tried to free a NULL pointer; i=%lu n=%lu\n",
+                                 i, number);
                         continue;
                 }
                 __free_page(pages[i]);
@@ -592,7 +593,7 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
         end = offset + len;
 
         if (end > b->bm_words) {
-                printk(KERN_ALERT "drbd: bm_memset end > bm_words\n");
+                pr_alert("bm_memset end > bm_words\n");
                 return;
         }
 
@@ -602,7 +603,7 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
                 p_addr = bm_map_pidx(b, idx);
                 bm = p_addr + MLPP(offset);
                 if (bm+do_now > p_addr + LWPP) {
-                        printk(KERN_ALERT "drbd: BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
+                        pr_alert("BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
                                p_addr, bm, (int)do_now);
                 } else
                         memset(bm, c, do_now * sizeof(long));
@@ -927,22 +928,14 @@ void drbd_bm_clear_all(struct drbd_device *device)
         spin_unlock_irq(&b->bm_lock);
 }
 
-struct bm_aio_ctx {
-        struct drbd_device *device;
-        atomic_t in_flight;
-        unsigned int done;
-        unsigned flags;
-#define BM_AIO_COPY_PAGES       1
-#define BM_AIO_WRITE_HINTED     2
-#define BM_WRITE_ALL_PAGES      4
-        int error;
-        struct kref kref;
-};
-
-static void bm_aio_ctx_destroy(struct kref *kref)
+static void drbd_bm_aio_ctx_destroy(struct kref *kref)
 {
-        struct bm_aio_ctx *ctx = container_of(kref, struct bm_aio_ctx, kref);
+        struct drbd_bm_aio_ctx *ctx = container_of(kref, struct drbd_bm_aio_ctx, kref);
+        unsigned long flags;
 
+        spin_lock_irqsave(&ctx->device->resource->req_lock, flags);
+        list_del(&ctx->list);
+        spin_unlock_irqrestore(&ctx->device->resource->req_lock, flags);
         put_ldev(ctx->device);
         kfree(ctx);
 }
@@ -950,7 +943,7 @@ static void bm_aio_ctx_destroy(struct kref *kref)
 /* bv_page may be a copy, or may be the original */
 static void bm_async_io_complete(struct bio *bio, int error)
 {
-        struct bm_aio_ctx *ctx = bio->bi_private;
+        struct drbd_bm_aio_ctx *ctx = bio->bi_private;
         struct drbd_device *device = ctx->device;
         struct drbd_bitmap *b = device->bitmap;
         unsigned int idx = bm_page_to_idx(bio->bi_io_vec[0].bv_page);
@@ -993,17 +986,18 @@ static void bm_async_io_complete(struct bio *bio, int error)
         if (atomic_dec_and_test(&ctx->in_flight)) {
                 ctx->done = 1;
                 wake_up(&device->misc_wait);
-                kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+                kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
         }
 }
 
-static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must_hold(local)
+static void bm_page_io_async(struct drbd_bm_aio_ctx *ctx, int page_nr) __must_hold(local)
 {
         struct bio *bio = bio_alloc_drbd(GFP_NOIO);
         struct drbd_device *device = ctx->device;
         struct drbd_bitmap *b = device->bitmap;
         struct page *page;
         unsigned int len;
+        unsigned int rw = (ctx->flags & BM_AIO_READ) ? READ : WRITE;
 
         sector_t on_disk_sector =
                 device->ldev->md.md_offset + device->ldev->md.bm_offset;
@@ -1049,9 +1043,9 @@ static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must
 /*
  * bm_rw: read/write the whole bitmap from/to its on disk location.
  */
-static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned lazy_writeout_upper_idx) __must_hold(local)
+static int bm_rw(struct drbd_device *device, const unsigned int flags, unsigned lazy_writeout_upper_idx) __must_hold(local)
 {
-        struct bm_aio_ctx *ctx;
+        struct drbd_bm_aio_ctx *ctx;
         struct drbd_bitmap *b = device->bitmap;
         int num_pages, i, count = 0;
         unsigned long now;
@@ -1067,12 +1061,13 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
          * as we submit copies of pages anyways.
          */
 
-        ctx = kmalloc(sizeof(struct bm_aio_ctx), GFP_NOIO);
+        ctx = kmalloc(sizeof(struct drbd_bm_aio_ctx), GFP_NOIO);
         if (!ctx)
                 return -ENOMEM;
 
-        *ctx = (struct bm_aio_ctx) {
+        *ctx = (struct drbd_bm_aio_ctx) {
                 .device = device,
+                .start_jif = jiffies,
                 .in_flight = ATOMIC_INIT(1),
                 .done = 0,
                 .flags = flags,
@@ -1080,15 +1075,21 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
                 .kref = { ATOMIC_INIT(2) },
         };
 
-        if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in bm_aio_ctx_destroy() */
+        if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in drbd_bm_aio_ctx_destroy() */
                 drbd_err(device, "ASSERT FAILED: get_ldev_if_state() == 1 in bm_rw()\n");
                 kfree(ctx);
                 return -ENODEV;
         }
+        /* Here D_ATTACHING is sufficient since drbd_bm_read() is called only from
+           drbd_adm_attach(), after device->ldev was assigned. */
 
-        if (!ctx->flags)
+        if (0 == (ctx->flags & ~BM_AIO_READ))
                 WARN_ON(!(BM_LOCKED_MASK & b->bm_flags));
 
+        spin_lock_irq(&device->resource->req_lock);
+        list_add_tail(&ctx->list, &device->pending_bitmap_io);
+        spin_unlock_irq(&device->resource->req_lock);
+
         num_pages = b->bm_number_of_pages;
 
         now = jiffies;
@@ -1098,13 +1099,13 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
                 /* ignore completely unchanged pages */
                 if (lazy_writeout_upper_idx && i == lazy_writeout_upper_idx)
                         break;
-                if (rw & WRITE) {
+                if (!(flags & BM_AIO_READ)) {
                         if ((flags & BM_AIO_WRITE_HINTED) &&
                             !test_and_clear_bit(BM_PAGE_HINT_WRITEOUT,
                                     &page_private(b->bm_pages[i])))
                                 continue;
 
-                        if (!(flags & BM_WRITE_ALL_PAGES) &&
+                        if (!(flags & BM_AIO_WRITE_ALL_PAGES) &&
                             bm_test_page_unchanged(b->bm_pages[i])) {
                                 dynamic_drbd_dbg(device, "skipped bm write for idx %u\n", i);
                                 continue;
@@ -1118,7 +1119,7 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
                         }
                 }
                 atomic_inc(&ctx->in_flight);
-                bm_page_io_async(ctx, i, rw);
+                bm_page_io_async(ctx, i);
                 ++count;
                 cond_resched();
         }
@@ -1134,12 +1135,12 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
         if (!atomic_dec_and_test(&ctx->in_flight))
                 wait_until_done_or_force_detached(device, device->ldev, &ctx->done);
         else
-                kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+                kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
 
         /* summary for global bitmap IO */
         if (flags == 0)
                 drbd_info(device, "bitmap %s of %u pages took %lu jiffies\n",
-                         rw == WRITE ? "WRITE" : "READ",
+                         (flags & BM_AIO_READ) ? "READ" : "WRITE",
                          count, jiffies - now);
 
         if (ctx->error) {
@@ -1152,20 +1153,18 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
                 err = -EIO; /* Disk timeout/force-detach during IO... */
 
         now = jiffies;
-        if (rw == WRITE) {
-                drbd_md_flush(device);
-        } else /* rw == READ */ {
+        if (flags & BM_AIO_READ) {
                 b->bm_set = bm_count_bits(b);
                 drbd_info(device, "recounting of set bits took additional %lu jiffies\n",
                      jiffies - now);
         }
         now = b->bm_set;
 
-        if (flags == 0)
+        if ((flags & ~BM_AIO_READ) == 0)
                 drbd_info(device, "%s (%lu bits) marked out-of-sync by on disk bit-map.\n",
                      ppsize(ppb, now << (BM_BLOCK_SHIFT-10)), now);
 
-        kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+        kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
         return err;
 }
 
@@ -1175,7 +1174,7 @@ static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned la
  */
 int drbd_bm_read(struct drbd_device *device) __must_hold(local)
 {
-        return bm_rw(device, READ, 0, 0);
+        return bm_rw(device, BM_AIO_READ, 0);
 }
 
 /**
@@ -1186,7 +1185,7 @@ int drbd_bm_read(struct drbd_device *device) __must_hold(local)
  */
 int drbd_bm_write(struct drbd_device *device) __must_hold(local)
 {
-        return bm_rw(device, WRITE, 0, 0);
+        return bm_rw(device, 0, 0);
 }
 
 /**
@@ -1197,7 +1196,17 @@ int drbd_bm_write(struct drbd_device *device) __must_hold(local)
  */
 int drbd_bm_write_all(struct drbd_device *device) __must_hold(local)
 {
-        return bm_rw(device, WRITE, BM_WRITE_ALL_PAGES, 0);
+        return bm_rw(device, BM_AIO_WRITE_ALL_PAGES, 0);
+}
+
+/**
+ * drbd_bm_write_lazy() - Write bitmap pages 0 to @upper_idx-1, if they have changed.
+ * @device:     DRBD device.
+ * @upper_idx:  0: write all changed pages; +ve: page index to stop scanning for changed pages
+ */
+int drbd_bm_write_lazy(struct drbd_device *device, unsigned upper_idx) __must_hold(local)
+{
+        return bm_rw(device, BM_AIO_COPY_PAGES, upper_idx);
 }
 
 /**
@@ -1213,7 +1222,7 @@ int drbd_bm_write_all(struct drbd_device *device) __must_hold(local)
  */
 int drbd_bm_write_copy_pages(struct drbd_device *device) __must_hold(local)
 {
-        return bm_rw(device, WRITE, BM_AIO_COPY_PAGES, 0);
+        return bm_rw(device, BM_AIO_COPY_PAGES, 0);
 }
 
 /**
@@ -1222,62 +1231,7 @@ int drbd_bm_write_copy_pages(struct drbd_device *device) __must_hold(local)
  */
 int drbd_bm_write_hinted(struct drbd_device *device) __must_hold(local)
 {
-        return bm_rw(device, WRITE, BM_AIO_WRITE_HINTED | BM_AIO_COPY_PAGES, 0);
-}
-
-/**
- * drbd_bm_write_page() - Writes a PAGE_SIZE aligned piece of bitmap
- * @device:     DRBD device.
- * @idx:        bitmap page index
- *
- * We don't want to special case on logical_block_size of the backend device,
- * so we submit PAGE_SIZE aligned pieces.
- * Note that on "most" systems, PAGE_SIZE is 4k.
- *
- * In case this becomes an issue on systems with larger PAGE_SIZE,
- * we may want to change this again to write 4k aligned 4k pieces.
- */
-int drbd_bm_write_page(struct drbd_device *device, unsigned int idx) __must_hold(local)
-{
-        struct bm_aio_ctx *ctx;
-        int err;
-
-        if (bm_test_page_unchanged(device->bitmap->bm_pages[idx])) {
-                dynamic_drbd_dbg(device, "skipped bm page write for idx %u\n", idx);
-                return 0;
-        }
-
-        ctx = kmalloc(sizeof(struct bm_aio_ctx), GFP_NOIO);
-        if (!ctx)
-                return -ENOMEM;
-
-        *ctx = (struct bm_aio_ctx) {
-                .device = device,
-                .in_flight = ATOMIC_INIT(1),
-                .done = 0,
-                .flags = BM_AIO_COPY_PAGES,
-                .error = 0,
-                .kref = { ATOMIC_INIT(2) },
-        };
-
-        if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in bm_aio_ctx_destroy() */
-                drbd_err(device, "ASSERT FAILED: get_ldev_if_state() == 1 in drbd_bm_write_page()\n");
-                kfree(ctx);
-                return -ENODEV;
-        }
-
-        bm_page_io_async(ctx, idx, WRITE_SYNC);
-        wait_until_done_or_force_detached(device, device->ldev, &ctx->done);
-
-        if (ctx->error)
-                drbd_chk_io_error(device, 1, DRBD_META_IO_ERROR);
-                /* that causes us to detach, so the in memory bitmap will be
-                 * gone in a moment as well. */
-
-        device->bm_writ_cnt++;
-        err = atomic_read(&ctx->in_flight) ? -EIO : ctx->error;
-        kref_put(&ctx->kref, &bm_aio_ctx_destroy);
-        return err;
+        return bm_rw(device, BM_AIO_WRITE_HINTED | BM_AIO_COPY_PAGES, 0);
 }
 
 /* NOTE
diff --git a/drivers/block/drbd/drbd_debugfs.c b/drivers/block/drbd/drbd_debugfs.c
new file mode 100644
index 000000000000..5c20b18540b8
--- /dev/null
+++ b/drivers/block/drbd/drbd_debugfs.c
@@ -0,0 +1,958 @@
+#define pr_fmt(fmt) "drbd debugfs: " fmt
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/stat.h>
+#include <linux/jiffies.h>
+#include <linux/list.h>
+
+#include "drbd_int.h"
+#include "drbd_req.h"
+#include "drbd_debugfs.h"
+
+
+/**********************************************************************
+ * Whenever you change the file format, remember to bump the version. *
+ **********************************************************************/
+
+static struct dentry *drbd_debugfs_root;
+static struct dentry *drbd_debugfs_version;
+static struct dentry *drbd_debugfs_resources;
+static struct dentry *drbd_debugfs_minors;
+
+static void seq_print_age_or_dash(struct seq_file *m, bool valid, unsigned long dt)
+{
+        if (valid)
+                seq_printf(m, "\t%d", jiffies_to_msecs(dt));
+        else
+                seq_printf(m, "\t-");
+}
+
+static void __seq_print_rq_state_bit(struct seq_file *m,
+        bool is_set, char *sep, const char *set_name, const char *unset_name)
+{
+        if (is_set && set_name) {
+                seq_putc(m, *sep);
+                seq_puts(m, set_name);
+                *sep = '|';
+        } else if (!is_set && unset_name) {
+                seq_putc(m, *sep);
+                seq_puts(m, unset_name);
+                *sep = '|';
+        }
+}
+
+static void seq_print_rq_state_bit(struct seq_file *m,
+        bool is_set, char *sep, const char *set_name)
+{
+        __seq_print_rq_state_bit(m, is_set, sep, set_name, NULL);
+}
+
+/* pretty print enum drbd_req_state_bits req->rq_state */
+static void seq_print_request_state(struct seq_file *m, struct drbd_request *req)
+{
+        unsigned int s = req->rq_state;
+        char sep = ' ';
+        seq_printf(m, "\t0x%08x", s);
+        seq_printf(m, "\tmaster: %s", req->master_bio ? "pending" : "completed");
+
+        /* RQ_WRITE ignored, already reported */
+        seq_puts(m, "\tlocal:");
+        seq_print_rq_state_bit(m, s & RQ_IN_ACT_LOG, &sep, "in-AL");
+        seq_print_rq_state_bit(m, s & RQ_POSTPONED, &sep, "postponed");
+        seq_print_rq_state_bit(m, s & RQ_COMPLETION_SUSP, &sep, "suspended");
+        sep = ' ';
+        seq_print_rq_state_bit(m, s & RQ_LOCAL_PENDING, &sep, "pending");
+        seq_print_rq_state_bit(m, s & RQ_LOCAL_COMPLETED, &sep, "completed");
+        seq_print_rq_state_bit(m, s & RQ_LOCAL_ABORTED, &sep, "aborted");
+        seq_print_rq_state_bit(m, s & RQ_LOCAL_OK, &sep, "ok");
+        if (sep == ' ')
+                seq_puts(m, " -");
+
+        /* for_each_connection ... */
+        seq_printf(m, "\tnet:");
+        sep = ' ';
+        seq_print_rq_state_bit(m, s & RQ_NET_PENDING, &sep, "pending");
+        seq_print_rq_state_bit(m, s & RQ_NET_QUEUED, &sep, "queued");
+        seq_print_rq_state_bit(m, s & RQ_NET_SENT, &sep, "sent");
+        seq_print_rq_state_bit(m, s & RQ_NET_DONE, &sep, "done");
+        seq_print_rq_state_bit(m, s & RQ_NET_SIS, &sep, "sis");
+        seq_print_rq_state_bit(m, s & RQ_NET_OK, &sep, "ok");
+        if (sep == ' ')
+                seq_puts(m, " -");
+
+        seq_printf(m, " :");
+        sep = ' ';
+        seq_print_rq_state_bit(m, s & RQ_EXP_RECEIVE_ACK, &sep, "B");
+        seq_print_rq_state_bit(m, s & RQ_EXP_WRITE_ACK, &sep, "C");
+        seq_print_rq_state_bit(m, s & RQ_EXP_BARR_ACK, &sep, "barr");
+        if (sep == ' ')
+                seq_puts(m, " -");
+        seq_printf(m, "\n");
+}
+
+static void seq_print_one_request(struct seq_file *m, struct drbd_request *req, unsigned long now)
+{
+        /* change anything here, fixup header below! */
+        unsigned int s = req->rq_state;
+
+#define RQ_HDR_1 "epoch\tsector\tsize\trw"
+        seq_printf(m, "0x%x\t%llu\t%u\t%s",
+                req->epoch,
+                (unsigned long long)req->i.sector, req->i.size >> 9,
+                (s & RQ_WRITE) ? "W" : "R");
+
+#define RQ_HDR_2 "\tstart\tin AL\tsubmit"
+        seq_printf(m, "\t%d", jiffies_to_msecs(now - req->start_jif));
+        seq_print_age_or_dash(m, s & RQ_IN_ACT_LOG, now - req->in_actlog_jif);
+        seq_print_age_or_dash(m, s & RQ_LOCAL_PENDING, now - req->pre_submit_jif);
+
+#define RQ_HDR_3 "\tsent\tacked\tdone"
+        seq_print_age_or_dash(m, s & RQ_NET_SENT, now - req->pre_send_jif);
+        seq_print_age_or_dash(m, (s & RQ_NET_SENT) && !(s & RQ_NET_PENDING), now - req->acked_jif);
+        seq_print_age_or_dash(m, s & RQ_NET_DONE, now - req->net_done_jif);
+
+#define RQ_HDR_4 "\tstate\n"
+        seq_print_request_state(m, req);
+}
+#define RQ_HDR RQ_HDR_1 RQ_HDR_2 RQ_HDR_3 RQ_HDR_4
+
+static void seq_print_minor_vnr_req(struct seq_file *m, struct drbd_request *req, unsigned long now)
+{
+        seq_printf(m, "%u\t%u\t", req->device->minor, req->device->vnr);
+        seq_print_one_request(m, req, now);
+}
+
+static void seq_print_resource_pending_meta_io(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
+{
+        struct drbd_device *device;
+        unsigned int i;
+
+        seq_puts(m, "minor\tvnr\tstart\tsubmit\tintent\n");
+        rcu_read_lock();
+        idr_for_each_entry(&resource->devices, device, i) {
+                struct drbd_md_io tmp;
+                /* In theory this is racy,
+                 * in the sense that there could have been a
+                 * drbd_md_put_buffer(); drbd_md_get_buffer();
+                 * between accessing these members here.  */
+                tmp = device->md_io;
+                if (atomic_read(&tmp.in_use)) {
+                        seq_printf(m, "%u\t%u\t%d\t",
+                                device->minor, device->vnr,
+                                jiffies_to_msecs(now - tmp.start_jif));
+                        if (time_before(tmp.submit_jif, tmp.start_jif))
+                                seq_puts(m, "-\t");
+                        else
+                                seq_printf(m, "%d\t", jiffies_to_msecs(now - tmp.submit_jif));
+                        seq_printf(m, "%s\n", tmp.current_use);
+                }
+        }
+        rcu_read_unlock();
+}
+
+static void seq_print_waiting_for_AL(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
+{
+        struct drbd_device *device;
+        unsigned int i;
+
+        seq_puts(m, "minor\tvnr\tage\t#waiting\n");
+        rcu_read_lock();
+        idr_for_each_entry(&resource->devices, device, i) {
+                unsigned long jif;
+                struct drbd_request *req;
+                int n = atomic_read(&device->ap_actlog_cnt);
+                if (n) {
+                        spin_lock_irq(&device->resource->req_lock);
+                        req = list_first_entry_or_null(&device->pending_master_completion[1],
+                                struct drbd_request, req_pending_master_completion);
+                        /* if the oldest request does not wait for the activity log
+                         * it is not interesting for us here */
+                        if (req && !(req->rq_state & RQ_IN_ACT_LOG))
+                                jif = req->start_jif;
+                        else
+                                req = NULL;
+                        spin_unlock_irq(&device->resource->req_lock);
+                }
+                if (n) {
+                        seq_printf(m, "%u\t%u\t", device->minor, device->vnr);
+                        if (req)
+                                seq_printf(m, "%u\t", jiffies_to_msecs(now - jif));
+                        else
+                                seq_puts(m, "-\t");
+                        seq_printf(m, "%u\n", n);
+                }
+        }
+        rcu_read_unlock();
+}
+
+static void seq_print_device_bitmap_io(struct seq_file *m, struct drbd_device *device, unsigned long now)
+{
+        struct drbd_bm_aio_ctx *ctx;
+        unsigned long start_jif;
+        unsigned int in_flight;
+        unsigned int flags;
+        spin_lock_irq(&device->resource->req_lock);
+        ctx = list_first_entry_or_null(&device->pending_bitmap_io, struct drbd_bm_aio_ctx, list);
+        if (ctx && ctx->done)
+                ctx = NULL;
+        if (ctx) {
+                start_jif = ctx->start_jif;
+                in_flight = atomic_read(&ctx->in_flight);
+                flags = ctx->flags;
+        }
+        spin_unlock_irq(&device->resource->req_lock);
+        if (ctx) {
+                seq_printf(m, "%u\t%u\t%c\t%u\t%u\n",
+                        device->minor, device->vnr,
+                        (flags & BM_AIO_READ) ? 'R' : 'W',
+                        jiffies_to_msecs(now - start_jif),
+                        in_flight);
+        }
+}
+
+static void seq_print_resource_pending_bitmap_io(struct seq_file *m, struct drbd_resource *resource, unsigned long now)
+{
+        struct drbd_device *device;
+        unsigned int i;
+
+        seq_puts(m, "minor\tvnr\trw\tage\t#in-flight\n");
+        rcu_read_lock();
+        idr_for_each_entry(&resource->devices, device, i) {
+                seq_print_device_bitmap_io(m, device, now);
+        }
+        rcu_read_unlock();
+}
+
+/* pretty print enum peer_req->flags */
+static void seq_print_peer_request_flags(struct seq_file *m, struct drbd_peer_request *peer_req)
+{
+        unsigned long f = peer_req->flags;
+        char sep = ' ';
+
+        __seq_print_rq_state_bit(m, f & EE_SUBMITTED, &sep, "submitted", "preparing");
+        __seq_print_rq_state_bit(m, f & EE_APPLICATION, &sep, "application", "internal");
+        seq_print_rq_state_bit(m, f & EE_CALL_AL_COMPLETE_IO, &sep, "in-AL");
+        seq_print_rq_state_bit(m, f & EE_SEND_WRITE_ACK, &sep, "C");
+        seq_print_rq_state_bit(m, f & EE_MAY_SET_IN_SYNC, &sep, "set-in-sync");
+
+        if (f & EE_IS_TRIM) {
+                seq_putc(m, sep);
+                sep = '|';
+                if (f & EE_IS_TRIM_USE_ZEROOUT)
+                        seq_puts(m, "zero-out");
+                else
+                        seq_puts(m, "trim");
+        }
+        seq_putc(m, '\n');
+}
+
+static void seq_print_peer_request(struct seq_file *m,
+        struct drbd_device *device, struct list_head *lh,
+        unsigned long now)
+{
+        bool reported_preparing = false;
+        struct drbd_peer_request *peer_req;
+        list_for_each_entry(peer_req, lh, w.list) {
+                if (reported_preparing && !(peer_req->flags & EE_SUBMITTED))
+                        continue;
+
+                if (device)
+                        seq_printf(m, "%u\t%u\t", device->minor, device->vnr);
+
+                seq_printf(m, "%llu\t%u\t%c\t%u\t",
+                        (unsigned long long)peer_req->i.sector, peer_req->i.size >> 9,
+                        (peer_req->flags & EE_WRITE) ? 'W' : 'R',
+                        jiffies_to_msecs(now - peer_req->submit_jif));
+                seq_print_peer_request_flags(m, peer_req);
+                if (peer_req->flags & EE_SUBMITTED)
+                        break;
+                else
+                        reported_preparing = true;
+        }
+}
+
+static void seq_print_device_peer_requests(struct seq_file *m,
+        struct drbd_device *device, unsigned long now)
+{
+        seq_puts(m, "minor\tvnr\tsector\tsize\trw\tage\tflags\n");
+        spin_lock_irq(&device->resource->req_lock);
+        seq_print_peer_request(m, device, &device->active_ee, now);
+        seq_print_peer_request(m, device, &device->read_ee, now);
+        seq_print_peer_request(m, device, &device->sync_ee, now);
+        spin_unlock_irq(&device->resource->req_lock);
+        if (test_bit(FLUSH_PENDING, &device->flags)) {
+                seq_printf(m, "%u\t%u\t-\t-\tF\t%u\tflush\n",
+                        device->minor, device->vnr,
+                        jiffies_to_msecs(now - device->flush_jif));
+        }
+}
+
+static void seq_print_resource_pending_peer_requests(struct seq_file *m,
+        struct drbd_resource *resource, unsigned long now)
+{
+        struct drbd_device *device;
+        unsigned int i;
+
+        rcu_read_lock();
+        idr_for_each_entry(&resource->devices, device, i) {
+                seq_print_device_peer_requests(m, device, now);
+        }
+        rcu_read_unlock();
+}
+
+static void seq_print_resource_transfer_log_summary(struct seq_file *m,
+        struct drbd_resource *resource,
+        struct drbd_connection *connection,
+        unsigned long now)
+{
+        struct drbd_request *req;
+        unsigned int count = 0;
+        unsigned int show_state = 0;
+
+        seq_puts(m, "n\tdevice\tvnr\t" RQ_HDR);
+        spin_lock_irq(&resource->req_lock);
+        list_for_each_entry(req, &connection->transfer_log, tl_requests) {
+                unsigned int tmp = 0;
+                unsigned int s;
+                ++count;
+
+                /* don't disable irq "forever" */
+                if (!(count & 0x1ff)) {
+                        struct drbd_request *req_next;
+                        kref_get(&req->kref);
+                        spin_unlock_irq(&resource->req_lock);
+                        cond_resched();
+                        spin_lock_irq(&resource->req_lock);
+                        req_next = list_next_entry(req, tl_requests);
+                        if (kref_put(&req->kref, drbd_req_destroy))
+                                req = req_next;
+                        if (&req->tl_requests == &connection->transfer_log)
+                                break;
+                }
+
+                s = req->rq_state;
+
+                /* This is meant to summarize timing issues, to be able to tell
+                 * local disk problems from network problems.
+                 * Skip requests, if we have shown an even older request with
+                 * similar aspects already.  */
+                if (req->master_bio == NULL)
+                        tmp |= 1;
+                if ((s & RQ_LOCAL_MASK) && (s & RQ_LOCAL_PENDING))
+                        tmp |= 2;
+                if (s & RQ_NET_MASK) {
+                        if (!(s & RQ_NET_SENT))
+                                tmp |= 4;
+                        if (s & RQ_NET_PENDING)
+                                tmp |= 8;
+                        if (!(s & RQ_NET_DONE))
+                                tmp |= 16;
+                }
+                if ((tmp & show_state) == tmp)
+                        continue;
+                show_state |= tmp;
+                seq_printf(m, "%u\t", count);
+                seq_print_minor_vnr_req(m, req, now);
+                if (show_state == 0x1f)
+                        break;
+        }
+        spin_unlock_irq(&resource->req_lock);
+}
+
+/* TODO: transfer_log and friends should be moved to resource */
+static int in_flight_summary_show(struct seq_file *m, void *pos)
+{
+        struct drbd_resource *resource = m->private;
+        struct drbd_connection *connection;
+        unsigned long jif = jiffies;
+
+        connection = first_connection(resource);
+        /* This does not happen, actually.
+         * But be robust and prepare for future code changes. */
+        if (!connection || !kref_get_unless_zero(&connection->kref))
+                return -ESTALE;
+
+        /* BUMP me if you change the file format/content/presentation */
+        seq_printf(m, "v: %u\n\n", 0);
+
+        seq_puts(m, "oldest bitmap IO\n");
+        seq_print_resource_pending_bitmap_io(m, resource, jif);
+        seq_putc(m, '\n');
+
+        seq_puts(m, "meta data IO\n");
+        seq_print_resource_pending_meta_io(m, resource, jif);
+        seq_putc(m, '\n');
+
+        seq_puts(m, "socket buffer stats\n");
+        /* for each connection ... once we have more than one */
+        rcu_read_lock();
+        if (connection->data.socket) {
+                /* open coded SIOCINQ, the "relevant" part */
+                struct tcp_sock *tp = tcp_sk(connection->data.socket->sk);
+                int answ = tp->rcv_nxt - tp->copied_seq;
+                seq_printf(m, "unread receive buffer: %u Byte\n", answ);
+                /* open coded SIOCOUTQ, the "relevant" part */
+                answ = tp->write_seq - tp->snd_una;
+                seq_printf(m, "unacked send buffer: %u Byte\n", answ);
+        }
+        rcu_read_unlock();
+        seq_putc(m, '\n');
+
+        seq_puts(m, "oldest peer requests\n");
+        seq_print_resource_pending_peer_requests(m, resource, jif);
+        seq_putc(m, '\n');
+
+        seq_puts(m, "application requests waiting for activity log\n");
+        seq_print_waiting_for_AL(m, resource, jif);
+        seq_putc(m, '\n');
+
+        seq_puts(m, "oldest application requests\n");
+        seq_print_resource_transfer_log_summary(m, resource, connection, jif);
+        seq_putc(m, '\n');
+
+        jif = jiffies - jif;
+        if (jif)
+                seq_printf(m, "generated in %d ms\n", jiffies_to_msecs(jif));
+        kref_put(&connection->kref, drbd_destroy_connection);
+        return 0;
+}
+
+/* simple_positive(file->f_dentry) respectively debugfs_positive(),
+ * but neither is "reachable" from here.
+ * So we have our own inline version of it above.  :-( */
+static inline int debugfs_positive(struct dentry *dentry)
+{
+        return dentry->d_inode && !d_unhashed(dentry);
+}
+
+/* make sure at *open* time that the respective object won't go away. */
+static int drbd_single_open(struct file *file, int (*show)(struct seq_file *, void *),
+                                void *data, struct kref *kref,
+                                void (*release)(struct kref *))
+{
+        struct dentry *parent;
+        int ret = -ESTALE;
+
+        /* Are we still linked,
+         * or has debugfs_remove() already been called? */
+        parent = file->f_dentry->d_parent;
+        /* not sure if this can happen: */
+        if (!parent || !parent->d_inode)
+                goto out;
+        /* serialize with d_delete() */
+        mutex_lock(&parent->d_inode->i_mutex);
+        /* Make sure the object is still alive */
+        if (debugfs_positive(file->f_dentry)
+        && kref_get_unless_zero(kref))
+                ret = 0;
+        mutex_unlock(&parent->d_inode->i_mutex);
+        if (!ret) {
+                ret = single_open(file, show, data);
+                if (ret)
+                        kref_put(kref, release);
+        }
+out:
+        return ret;
+}
+
+static int in_flight_summary_open(struct inode *inode, struct file *file)
+{
+        struct drbd_resource *resource = inode->i_private;
+        return drbd_single_open(file, in_flight_summary_show, resource,
+                                &resource->kref, drbd_destroy_resource);
+}
+
+static int in_flight_summary_release(struct inode *inode, struct file *file)
+{
+        struct drbd_resource *resource = inode->i_private;
+        kref_put(&resource->kref, drbd_destroy_resource);
+        return single_release(inode, file);
+}
+
+static const struct file_operations in_flight_summary_fops = {
+        .owner          = THIS_MODULE,
+        .open           = in_flight_summary_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = in_flight_summary_release,
+};
+
+void drbd_debugfs_resource_add(struct drbd_resource *resource)
+{
+        struct dentry *dentry;
+        if (!drbd_debugfs_resources)
+                return;
+
+        dentry = debugfs_create_dir(resource->name, drbd_debugfs_resources);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        resource->debugfs_res = dentry;
+
+        dentry = debugfs_create_dir("volumes", resource->debugfs_res);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        resource->debugfs_res_volumes = dentry;
+
+        dentry = debugfs_create_dir("connections", resource->debugfs_res);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        resource->debugfs_res_connections = dentry;
+
+        dentry = debugfs_create_file("in_flight_summary", S_IRUSR|S_IRGRP,
+                        resource->debugfs_res, resource,
+                        &in_flight_summary_fops);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        resource->debugfs_res_in_flight_summary = dentry;
+        return;
+
+fail:
+        drbd_debugfs_resource_cleanup(resource);
+        drbd_err(resource, "failed to create debugfs dentry\n");
+}
+
+static void drbd_debugfs_remove(struct dentry **dp)
+{
+        debugfs_remove(*dp);
+        *dp = NULL;
+}
+
+void drbd_debugfs_resource_cleanup(struct drbd_resource *resource)
+{
+        /* it is ok to call debugfs_remove(NULL) */
+        drbd_debugfs_remove(&resource->debugfs_res_in_flight_summary);
+        drbd_debugfs_remove(&resource->debugfs_res_connections);
+        drbd_debugfs_remove(&resource->debugfs_res_volumes);
+        drbd_debugfs_remove(&resource->debugfs_res);
+}
+
+static void seq_print_one_timing_detail(struct seq_file *m,
+        const struct drbd_thread_timing_details *tdp,
+        unsigned long now)
+{
+        struct drbd_thread_timing_details td;
+        /* No locking...
+         * use temporary assignment to get at consistent data. */
+        do {
+                td = *tdp;
+        } while (td.cb_nr != tdp->cb_nr);
+        if (!td.cb_addr)
+                return;
+        seq_printf(m, "%u\t%d\t%s:%u\t%ps\n",
+                        td.cb_nr,
+                        jiffies_to_msecs(now - td.start_jif),
+                        td.caller_fn, td.line,
+                        td.cb_addr);
+}
+
+static void seq_print_timing_details(struct seq_file *m,
+                const char *title,
+                unsigned int cb_nr, struct drbd_thread_timing_details *tdp, unsigned long now)
+{
+        unsigned int start_idx;
+        unsigned int i;
+
+        seq_printf(m, "%s\n", title);
+        /* If not much is going on, this will result in natural ordering.
+         * If it is very busy, we will possibly skip events, or even see wrap
+         * arounds, which could only be avoided with locking.
+         */
+        start_idx = cb_nr % DRBD_THREAD_DETAILS_HIST;
+        for (i = start_idx; i < DRBD_THREAD_DETAILS_HIST; i++)
+                seq_print_one_timing_detail(m, tdp+i, now);
+        for (i = 0; i < start_idx; i++)
+                seq_print_one_timing_detail(m, tdp+i, now);
+}
+
+static int callback_history_show(struct seq_file *m, void *ignored)
+{
+        struct drbd_connection *connection = m->private;
+        unsigned long jif = jiffies;
+
+        /* BUMP me if you change the file format/content/presentation */
+        seq_printf(m, "v: %u\n\n", 0);
+
+        seq_puts(m, "n\tage\tcallsite\tfn\n");
+        seq_print_timing_details(m, "worker", connection->w_cb_nr, connection->w_timing_details, jif);
+        seq_print_timing_details(m, "receiver", connection->r_cb_nr, connection->r_timing_details, jif);
+        return 0;
+}
+
+static int callback_history_open(struct inode *inode, struct file *file)
+{
+        struct drbd_connection *connection = inode->i_private;
+        return drbd_single_open(file, callback_history_show, connection,
+                                &connection->kref, drbd_destroy_connection);
+}
+
+static int callback_history_release(struct inode *inode, struct file *file)
+{
+        struct drbd_connection *connection = inode->i_private;
+        kref_put(&connection->kref, drbd_destroy_connection);
+        return single_release(inode, file);
+}
+
+static const struct file_operations connection_callback_history_fops = {
+        .owner          = THIS_MODULE,
+        .open           = callback_history_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = callback_history_release,
+};
+
+static int connection_oldest_requests_show(struct seq_file *m, void *ignored)
+{
+        struct drbd_connection *connection = m->private;
+        unsigned long now = jiffies;
+        struct drbd_request *r1, *r2;
+
+        /* BUMP me if you change the file format/content/presentation */
+        seq_printf(m, "v: %u\n\n", 0);
+
+        spin_lock_irq(&connection->resource->req_lock);
+        r1 = connection->req_next;
+        if (r1)
+                seq_print_minor_vnr_req(m, r1, now);
+        r2 = connection->req_ack_pending;
+        if (r2 && r2 != r1) {
+                r1 = r2;
+                seq_print_minor_vnr_req(m, r1, now);
+        }
+        r2 = connection->req_not_net_done;
+        if (r2 && r2 != r1)
+                seq_print_minor_vnr_req(m, r2, now);
+        spin_unlock_irq(&connection->resource->req_lock);
+        return 0;
+}
+
+static int connection_oldest_requests_open(struct inode *inode, struct file *file)
+{
+        struct drbd_connection *connection = inode->i_private;
+        return drbd_single_open(file, connection_oldest_requests_show, connection,
+                                &connection->kref, drbd_destroy_connection);
+}
+
+static int connection_oldest_requests_release(struct inode *inode, struct file *file)
+{
+        struct drbd_connection *connection = inode->i_private;
+        kref_put(&connection->kref, drbd_destroy_connection);
+        return single_release(inode, file);
+}
+
+static const struct file_operations connection_oldest_requests_fops = {
+        .owner          = THIS_MODULE,
+        .open           = connection_oldest_requests_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = connection_oldest_requests_release,
+};
+
+void drbd_debugfs_connection_add(struct drbd_connection *connection)
+{
+        struct dentry *conns_dir = connection->resource->debugfs_res_connections;
+        struct dentry *dentry;
+        if (!conns_dir)
+                return;
+
+        /* Once we enable mutliple peers,
+         * these connections will have descriptive names.
+         * For now, it is just the one connection to the (only) "peer". */
+        dentry = debugfs_create_dir("peer", conns_dir);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        connection->debugfs_conn = dentry;
+
+        dentry = debugfs_create_file("callback_history", S_IRUSR|S_IRGRP,
+                        connection->debugfs_conn, connection,
+                        &connection_callback_history_fops);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        connection->debugfs_conn_callback_history = dentry;
+
+        dentry = debugfs_create_file("oldest_requests", S_IRUSR|S_IRGRP,
+                        connection->debugfs_conn, connection,
+                        &connection_oldest_requests_fops);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        connection->debugfs_conn_oldest_requests = dentry;
+        return;
+
+fail:
+        drbd_debugfs_connection_cleanup(connection);
+        drbd_err(connection, "failed to create debugfs dentry\n");
+}
+
+void drbd_debugfs_connection_cleanup(struct drbd_connection *connection)
+{
+        drbd_debugfs_remove(&connection->debugfs_conn_callback_history);
+        drbd_debugfs_remove(&connection->debugfs_conn_oldest_requests);
+        drbd_debugfs_remove(&connection->debugfs_conn);
+}
+
+static void resync_dump_detail(struct seq_file *m, struct lc_element *e)
+{
+       struct bm_extent *bme = lc_entry(e, struct bm_extent, lce);
+
+       seq_printf(m, "%5d %s %s %s\n", bme->rs_left,
+                  test_bit(BME_NO_WRITES, &bme->flags) ? "NO_WRITES" : "---------",
+                  test_bit(BME_LOCKED, &bme->flags) ? "LOCKED" : "------",
+                  test_bit(BME_PRIORITY, &bme->flags) ? "PRIORITY" : "--------"
+                  );
+}
+
+static int device_resync_extents_show(struct seq_file *m, void *ignored)
+{
+        struct drbd_device *device = m->private;
+
+        /* BUMP me if you change the file format/content/presentation */
+        seq_printf(m, "v: %u\n\n", 0);
+
+        if (get_ldev_if_state(device, D_FAILED)) {
+                lc_seq_printf_stats(m, device->resync);
+                lc_seq_dump_details(m, device->resync, "rs_left flags", resync_dump_detail);
+                put_ldev(device);
+        }
+        return 0;
+}
+
+static int device_act_log_extents_show(struct seq_file *m, void *ignored)
+{
+        struct drbd_device *device = m->private;
+
+        /* BUMP me if you change the file format/content/presentation */
+        seq_printf(m, "v: %u\n\n", 0);
+
+        if (get_ldev_if_state(device, D_FAILED)) {
+                lc_seq_printf_stats(m, device->act_log);
+                lc_seq_dump_details(m, device->act_log, "", NULL);
+                put_ldev(device);
+        }
+        return 0;
+}
+
+static int device_oldest_requests_show(struct seq_file *m, void *ignored)
+{
+        struct drbd_device *device = m->private;
+        struct drbd_resource *resource = device->resource;
+        unsigned long now = jiffies;
+        struct drbd_request *r1, *r2;
+        int i;
+
+        /* BUMP me if you change the file format/content/presentation */
+        seq_printf(m, "v: %u\n\n", 0);
+
+        seq_puts(m, RQ_HDR);
+        spin_lock_irq(&resource->req_lock);
+        /* WRITE, then READ */
+        for (i = 1; i >= 0; --i) {
+                r1 = list_first_entry_or_null(&device->pending_master_completion[i],
+                        struct drbd_request, req_pending_master_completion);
+                r2 = list_first_entry_or_null(&device->pending_completion[i],
+                        struct drbd_request, req_pending_local);
+                if (r1)
+                        seq_print_one_request(m, r1, now);
+                if (r2 && r2 != r1)
+                        seq_print_one_request(m, r2, now);
+        }
+        spin_unlock_irq(&resource->req_lock);
+        return 0;
+}
+
+static int device_data_gen_id_show(struct seq_file *m, void *ignored)
+{
+        struct drbd_device *device = m->private;
+        struct drbd_md *md;
+        enum drbd_uuid_index idx;
+
+        if (!get_ldev_if_state(device, D_FAILED))
+                return -ENODEV;
+
+        md = &device->ldev->md;
+        spin_lock_irq(&md->uuid_lock);
+        for (idx = UI_CURRENT; idx <= UI_HISTORY_END; idx++) {
+                seq_printf(m, "0x%016llX\n", md->uuid[idx]);
+        }
+        spin_unlock_irq(&md->uuid_lock);
+        put_ldev(device);
+        return 0;
+}
+
+#define drbd_debugfs_device_attr(name)                                          \
+static int device_ ## name ## _open(struct inode *inode, struct file *file)     \
+{                                                                               \
+        struct drbd_device *device = inode->i_private;                          \
+        return drbd_single_open(file, device_ ## name ## _show, device,         \
+                                &device->kref, drbd_destroy_device);            \
+}                                                                               \
+static int device_ ## name ## _release(struct inode *inode, struct file *file)  \
+{                                                                               \
+        struct drbd_device *device = inode->i_private;                          \
+        kref_put(&device->kref, drbd_destroy_device);                           \
+        return single_release(inode, file);                                     \
+}                                                                               \
+static const struct file_operations device_ ## name ## _fops = {                \
+        .owner          = THIS_MODULE,                                          \
+        .open           = device_ ## name ## _open,                             \
+        .read           = seq_read,                                             \
+        .llseek         = seq_lseek,                                            \
+        .release        = device_ ## name ## _release,                          \
+};
+
+drbd_debugfs_device_attr(oldest_requests)
+drbd_debugfs_device_attr(act_log_extents)
+drbd_debugfs_device_attr(resync_extents)
+drbd_debugfs_device_attr(data_gen_id)
+
+void drbd_debugfs_device_add(struct drbd_device *device)
+{
+        struct dentry *vols_dir = device->resource->debugfs_res_volumes;
+        char minor_buf[8]; /* MINORMASK, MINORBITS == 20; */
+        char vnr_buf[8];   /* volume number vnr is even 16 bit only; */
+        char *slink_name = NULL;
+
+        struct dentry *dentry;
+        if (!vols_dir || !drbd_debugfs_minors)
+                return;
+
+        snprintf(vnr_buf, sizeof(vnr_buf), "%u", device->vnr);
+        dentry = debugfs_create_dir(vnr_buf, vols_dir);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        device->debugfs_vol = dentry;
+
+        snprintf(minor_buf, sizeof(minor_buf), "%u", device->minor);
+        slink_name = kasprintf(GFP_KERNEL, "../resources/%s/volumes/%u",
+                        device->resource->name, device->vnr);
+        if (!slink_name)
+                goto fail;
+        dentry = debugfs_create_symlink(minor_buf, drbd_debugfs_minors, slink_name);
+        kfree(slink_name);
+        slink_name = NULL;
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        device->debugfs_minor = dentry;
+
+#define DCF(name)       do {                                    \
+        dentry = debugfs_create_file(#name, S_IRUSR|S_IRGRP,    \
+                        device->debugfs_vol, device,            \
+                        &device_ ## name ## _fops);             \
+        if (IS_ERR_OR_NULL(dentry))                             \
+                goto fail;                                      \
+        device->debugfs_vol_ ## name = dentry;                  \
+        } while (0)
+
+        DCF(oldest_requests);
+        DCF(act_log_extents);
+        DCF(resync_extents);
+        DCF(data_gen_id);
+#undef DCF
+        return;
+
+fail:
+        drbd_debugfs_device_cleanup(device);
+        drbd_err(device, "failed to create debugfs entries\n");
+}
+
+void drbd_debugfs_device_cleanup(struct drbd_device *device)
+{
+        drbd_debugfs_remove(&device->debugfs_minor);
+        drbd_debugfs_remove(&device->debugfs_vol_oldest_requests);
+        drbd_debugfs_remove(&device->debugfs_vol_act_log_extents);
+        drbd_debugfs_remove(&device->debugfs_vol_resync_extents);
+        drbd_debugfs_remove(&device->debugfs_vol_data_gen_id);
+        drbd_debugfs_remove(&device->debugfs_vol);
+}
+
+void drbd_debugfs_peer_device_add(struct drbd_peer_device *peer_device)
+{
+        struct dentry *conn_dir = peer_device->connection->debugfs_conn;
+        struct dentry *dentry;
+        char vnr_buf[8];
+
+        if (!conn_dir)
+                return;
+
+        snprintf(vnr_buf, sizeof(vnr_buf), "%u", peer_device->device->vnr);
+        dentry = debugfs_create_dir(vnr_buf, conn_dir);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        peer_device->debugfs_peer_dev = dentry;
+        return;
+
+fail:
+        drbd_debugfs_peer_device_cleanup(peer_device);
+        drbd_err(peer_device, "failed to create debugfs entries\n");
+}
+
+void drbd_debugfs_peer_device_cleanup(struct drbd_peer_device *peer_device)
+{
+        drbd_debugfs_remove(&peer_device->debugfs_peer_dev);
+}
+
+static int drbd_version_show(struct seq_file *m, void *ignored)
+{
+        seq_printf(m, "# %s\n", drbd_buildtag());
+        seq_printf(m, "VERSION=%s\n", REL_VERSION);
+        seq_printf(m, "API_VERSION=%u\n", API_VERSION);
+        seq_printf(m, "PRO_VERSION_MIN=%u\n", PRO_VERSION_MIN);
+        seq_printf(m, "PRO_VERSION_MAX=%u\n", PRO_VERSION_MAX);
+        return 0;
+}
+
+static int drbd_version_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, drbd_version_show, NULL);
+}
+
+static struct file_operations drbd_version_fops = {
+        .owner = THIS_MODULE,
+        .open = drbd_version_open,
+        .llseek = seq_lseek,
+        .read = seq_read,
+        .release = single_release,
+};
+
+/* not __exit, may be indirectly called
+ * from the module-load-failure path as well. */
+void drbd_debugfs_cleanup(void)
+{
+        drbd_debugfs_remove(&drbd_debugfs_resources);
+        drbd_debugfs_remove(&drbd_debugfs_minors);
+        drbd_debugfs_remove(&drbd_debugfs_version);
+        drbd_debugfs_remove(&drbd_debugfs_root);
+}
+
+int __init drbd_debugfs_init(void)
+{
+        struct dentry *dentry;
+
+        dentry = debugfs_create_dir("drbd", NULL);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        drbd_debugfs_root = dentry;
+
+        dentry = debugfs_create_file("version", 0444, drbd_debugfs_root, NULL, &drbd_version_fops);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        drbd_debugfs_version = dentry;
+
+        dentry = debugfs_create_dir("resources", drbd_debugfs_root);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        drbd_debugfs_resources = dentry;
+
+        dentry = debugfs_create_dir("minors", drbd_debugfs_root);
+        if (IS_ERR_OR_NULL(dentry))
+                goto fail;
+        drbd_debugfs_minors = dentry;
+        return 0;
+
+fail:
+        drbd_debugfs_cleanup();
+        if (dentry)
+                return PTR_ERR(dentry);
+        else
+                return -EINVAL;
+}
diff --git a/drivers/block/drbd/drbd_debugfs.h b/drivers/block/drbd/drbd_debugfs.h
new file mode 100644
index 000000000000..8bee21340dce
--- /dev/null
+++ b/drivers/block/drbd/drbd_debugfs.h
@@ -0,0 +1,39 @@
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/debugfs.h>
+
+#include "drbd_int.h"
+
+#ifdef CONFIG_DEBUG_FS
+int __init drbd_debugfs_init(void);
+void drbd_debugfs_cleanup(void);
+
+void drbd_debugfs_resource_add(struct drbd_resource *resource);
+void drbd_debugfs_resource_cleanup(struct drbd_resource *resource);
+
+void drbd_debugfs_connection_add(struct drbd_connection *connection);
+void drbd_debugfs_connection_cleanup(struct drbd_connection *connection);
+
+void drbd_debugfs_device_add(struct drbd_device *device);
+void drbd_debugfs_device_cleanup(struct drbd_device *device);
+
+void drbd_debugfs_peer_device_add(struct drbd_peer_device *peer_device);
+void drbd_debugfs_peer_device_cleanup(struct drbd_peer_device *peer_device);
+#else
+
+static inline int __init drbd_debugfs_init(void) { return -ENODEV; }
+static inline void drbd_debugfs_cleanup(void) { }
+
+static inline void drbd_debugfs_resource_add(struct drbd_resource *resource) { }
+static inline void drbd_debugfs_resource_cleanup(struct drbd_resource *resource) { }
+
+static inline void drbd_debugfs_connection_add(struct drbd_connection *connection) { }
+static inline void drbd_debugfs_connection_cleanup(struct drbd_connection *connection) { }
+
+static inline void drbd_debugfs_device_add(struct drbd_device *device) { }
+static inline void drbd_debugfs_device_cleanup(struct drbd_device *device) { }
+
+static inline void drbd_debugfs_peer_device_add(struct drbd_peer_device *peer_device) { }
+static inline void drbd_debugfs_peer_device_cleanup(struct drbd_peer_device *peer_device) { }
+
+#endif
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index a76ceb344d64..1a000016ccdf 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -317,7 +317,63 @@ struct drbd_request {
 
         struct list_head tl_requests; /* ring list in the transfer log */
         struct bio *master_bio;       /* master bio pointer */
-        unsigned long start_time;
+
+        /* see struct drbd_device */
+        struct list_head req_pending_master_completion;
+        struct list_head req_pending_local;
+
+        /* for generic IO accounting */
+        unsigned long start_jif;
+
+        /* for DRBD internal statistics */
+
+        /* Minimal set of time stamps to determine if we wait for activity log
+         * transactions, local disk or peer.  32 bit "jiffies" are good enough,
+         * we don't expect a DRBD request to be stalled for several month.
+         */
+
+        /* before actual request processing */
+        unsigned long in_actlog_jif;
+
+        /* local disk */
+        unsigned long pre_submit_jif;
+
+        /* per connection */
+        unsigned long pre_send_jif;
+        unsigned long acked_jif;
+        unsigned long net_done_jif;
+
+        /* Possibly even more detail to track each phase:
+         *  master_completion_jif
+         *      how long did it take to complete the master bio
+         *      (application visible latency)
+         *  allocated_jif
+         *      how long the master bio was blocked until we finally allocated
+         *      a tracking struct
+         *  in_actlog_jif
+         *      how long did we wait for activity log transactions
+         *
+         *  net_queued_jif
+         *      when did we finally queue it for sending
+         *  pre_send_jif
+         *      when did we start sending it
+         *  post_send_jif
+         *      how long did we block in the network stack trying to send it
+         *  acked_jif
+         *      when did we receive (or fake, in protocol A) a remote ACK
+         *  net_done_jif
+         *      when did we receive final acknowledgement (P_BARRIER_ACK),
+         *      or decide, e.g. on connection loss, that we do no longer expect
+         *      anything from this peer for this request.
+         *
+         *  pre_submit_jif
+         *  post_sub_jif
+         *      when did we start submiting to the lower level device,
+         *      and how long did we block in that submit function
+         *  local_completion_jif
+         *      how long did it take the lower level device to complete this request
+         */
+
 
         /* once it hits 0, we may complete the master_bio */
         atomic_t completion_ref;
@@ -366,6 +422,7 @@ struct drbd_peer_request {
         struct drbd_interval i;
         /* see comments on ee flag bits below */
         unsigned long flags;
+        unsigned long submit_jif;
         union {
                 u64 block_id;
                 struct digest_info *digest;
@@ -408,6 +465,17 @@ enum {
 
         /* Is set when net_conf had two_primaries set while creating this peer_req */
         __EE_IN_INTERVAL_TREE,
+
+        /* for debugfs: */
+        /* has this been submitted, or does it still wait for something else? */
+        __EE_SUBMITTED,
+
+        /* this is/was a write request */
+        __EE_WRITE,
+
+        /* this originates from application on peer
+         * (not some resync or verify or other DRBD internal request) */
+        __EE_APPLICATION,
 };
 #define EE_CALL_AL_COMPLETE_IO (1<<__EE_CALL_AL_COMPLETE_IO)
 #define EE_MAY_SET_IN_SYNC     (1<<__EE_MAY_SET_IN_SYNC)
@@ -419,6 +487,9 @@ enum {
 #define EE_RESTART_REQUESTS     (1<<__EE_RESTART_REQUESTS)
 #define EE_SEND_WRITE_ACK       (1<<__EE_SEND_WRITE_ACK)
 #define EE_IN_INTERVAL_TREE     (1<<__EE_IN_INTERVAL_TREE)
+#define EE_SUBMITTED            (1<<__EE_SUBMITTED)
+#define EE_WRITE                (1<<__EE_WRITE)
+#define EE_APPLICATION          (1<<__EE_APPLICATION)
 
 /* flag bits per device */
 enum {
@@ -433,11 +504,11 @@ enum {
         CONSIDER_RESYNC,
 
         MD_NO_FUA,              /* Users wants us to not use FUA/FLUSH on meta data dev */
+
         SUSPEND_IO,             /* suspend application io */
         BITMAP_IO,              /* suspend application io;
                                    once no more io in flight, start bitmap io */
         BITMAP_IO_QUEUED,       /* Started bitmap IO */
-        GO_DISKLESS,            /* Disk is being detached, on io-error or admin request. */
         WAS_IO_ERROR,           /* Local disk failed, returned IO error */
         WAS_READ_ERROR,         /* Local disk READ failed (set additionally to the above) */
         FORCE_DETACH,           /* Force-detach from local disk, aborting any pending local IO */
@@ -450,6 +521,20 @@ enum {
         B_RS_H_DONE,            /* Before resync handler done (already executed) */
         DISCARD_MY_DATA,        /* discard_my_data flag per volume */
         READ_BALANCE_RR,
+
+        FLUSH_PENDING,          /* if set, device->flush_jif is when we submitted that flush
+                                 * from drbd_flush_after_epoch() */
+
+        /* cleared only after backing device related structures have been destroyed. */
+        GOING_DISKLESS,         /* Disk is being detached, because of io-error, or admin request. */
+
+        /* to be used in drbd_device_post_work() */
+        GO_DISKLESS,            /* tell worker to schedule cleanup before detach */
+        DESTROY_DISK,           /* tell worker to close backing devices and destroy related structures. */
+        MD_SYNC,                /* tell worker to call drbd_md_sync() */
+        RS_START,               /* tell worker to start resync/OV */
+        RS_PROGRESS,            /* tell worker that resync made significant progress */
+        RS_DONE,                /* tell worker that resync is done */
 };
 
 struct drbd_bitmap; /* opaque for drbd_device */
@@ -531,6 +616,11 @@ struct drbd_backing_dev {
 };
 
 struct drbd_md_io {
+        struct page *page;
+        unsigned long start_jif;        /* last call to drbd_md_get_buffer */
+        unsigned long submit_jif;       /* last _drbd_md_sync_page_io() submit */
+        const char *current_use;
+        atomic_t in_use;
         unsigned int done;
         int error;
 };
@@ -577,10 +667,18 @@ enum {
                                  * and potentially deadlock on, this drbd worker.
                                  */
         DISCONNECT_SENT,
+
+        DEVICE_WORK_PENDING,    /* tell worker that some device has pending work */
 };
 
 struct drbd_resource {
         char *name;
+#ifdef CONFIG_DEBUG_FS
+        struct dentry *debugfs_res;
+        struct dentry *debugfs_res_volumes;
+        struct dentry *debugfs_res_connections;
+        struct dentry *debugfs_res_in_flight_summary;
+#endif
         struct kref kref;
         struct idr devices;             /* volume number to device mapping */
         struct list_head connections;
@@ -594,12 +692,28 @@ struct drbd_resource {
         unsigned susp_nod:1;            /* IO suspended because no data */
         unsigned susp_fen:1;            /* IO suspended because fence peer handler runs */
 
+        enum write_ordering_e write_ordering;
+
         cpumask_var_t cpu_mask;
 };
 
+struct drbd_thread_timing_details
+{
+        unsigned long start_jif;
+        void *cb_addr;
+        const char *caller_fn;
+        unsigned int line;
+        unsigned int cb_nr;
+};
+
 struct drbd_connection {
         struct list_head connections;
         struct drbd_resource *resource;
+#ifdef CONFIG_DEBUG_FS
+        struct dentry *debugfs_conn;
+        struct dentry *debugfs_conn_callback_history;
+        struct dentry *debugfs_conn_oldest_requests;
+#endif
         struct kref kref;
         struct idr peer_devices;        /* volume number to peer device mapping */
         enum drbd_conns cstate;         /* Only C_STANDALONE to C_WF_REPORT_PARAMS */
@@ -636,7 +750,6 @@ struct drbd_connection {
         struct drbd_epoch *current_epoch;
         spinlock_t epoch_lock;
         unsigned int epochs;
-        enum write_ordering_e write_ordering;
         atomic_t current_tle_nr;        /* transfer log epoch number */
         unsigned current_tle_writes;    /* writes seen within this tl epoch */
 
@@ -645,9 +758,22 @@ struct drbd_connection {
         struct drbd_thread worker;
         struct drbd_thread asender;
 
+        /* cached pointers,
+         * so we can look up the oldest pending requests more quickly.
+         * protected by resource->req_lock */
+        struct drbd_request *req_next; /* DRBD 9: todo.req_next */
+        struct drbd_request *req_ack_pending;
+        struct drbd_request *req_not_net_done;
+
         /* sender side */
         struct drbd_work_queue sender_work;
 
+#define DRBD_THREAD_DETAILS_HIST        16
+        unsigned int w_cb_nr; /* keeps counting up */
+        unsigned int r_cb_nr; /* keeps counting up */
+        struct drbd_thread_timing_details w_timing_details[DRBD_THREAD_DETAILS_HIST];
+        struct drbd_thread_timing_details r_timing_details[DRBD_THREAD_DETAILS_HIST];
+
         struct {
                 /* whether this sender thread
                  * has processed a single write yet. */
@@ -663,11 +789,22 @@ struct drbd_connection {
         } send;
 };
 
+void __update_timing_details(
+                struct drbd_thread_timing_details *tdp,
+                unsigned int *cb_nr,
+                void *cb,
+                const char *fn, const unsigned int line);
+
+#define update_worker_timing_details(c, cb) \
+        __update_timing_details(c->w_timing_details, &c->w_cb_nr, cb, __func__ , __LINE__ )
+#define update_receiver_timing_details(c, cb) \
+        __update_timing_details(c->r_timing_details, &c->r_cb_nr, cb, __func__ , __LINE__ )
+
 struct submit_worker {
         struct workqueue_struct *wq;
         struct work_struct worker;
 
-        spinlock_t lock;
+        /* protected by ..->resource->req_lock */
         struct list_head writes;
 };
 
@@ -675,12 +812,29 @@ struct drbd_peer_device {
         struct list_head peer_devices;
         struct drbd_device *device;
         struct drbd_connection *connection;
+#ifdef CONFIG_DEBUG_FS
+        struct dentry *debugfs_peer_dev;
+#endif
 };
 
 struct drbd_device {
         struct drbd_resource *resource;
         struct list_head peer_devices;
-        int vnr;                        /* volume number within the connection */
+        struct list_head pending_bitmap_io;
+
+        unsigned long flush_jif;
+#ifdef CONFIG_DEBUG_FS
+        struct dentry *debugfs_minor;
+        struct dentry *debugfs_vol;
+        struct dentry *debugfs_vol_oldest_requests;
+        struct dentry *debugfs_vol_act_log_extents;
+        struct dentry *debugfs_vol_resync_extents;
+        struct dentry *debugfs_vol_data_gen_id;
+#endif
+
+        unsigned int vnr;       /* volume number within the connection */
+        unsigned int minor;     /* device minor number */
+
         struct kref kref;
 
         /* things that are stored as / read from meta data on disk */
@@ -697,19 +851,10 @@ struct drbd_device {
         unsigned long last_reattach_jif;
         struct drbd_work resync_work;
         struct drbd_work unplug_work;
-        struct drbd_work go_diskless;
-        struct drbd_work md_sync_work;
-        struct drbd_work start_resync_work;
         struct timer_list resync_timer;
         struct timer_list md_sync_timer;
         struct timer_list start_resync_timer;
         struct timer_list request_timer;
-#ifdef DRBD_DEBUG_MD_SYNC
-        struct {
-                unsigned int line;
-                const char* func;
-        } last_md_mark_dirty;
-#endif
 
         /* Used after attach while negotiating new disk state. */
         union drbd_state new_state_tmp;
@@ -724,6 +869,7 @@ struct drbd_device {
         unsigned int al_writ_cnt;
         unsigned int bm_writ_cnt;
         atomic_t ap_bio_cnt;     /* Requests we need to complete */
+        atomic_t ap_actlog_cnt;  /* Requests waiting for activity log */
         atomic_t ap_pending_cnt; /* AP data packets on the wire, ack expected */
         atomic_t rs_pending_cnt; /* RS request/data packets on the wire */
         atomic_t unacked_cnt;    /* Need to send replies for */
@@ -733,6 +879,13 @@ struct drbd_device {
         struct rb_root read_requests;
         struct rb_root write_requests;
 
+        /* for statistics and timeouts */
+        /* [0] read, [1] write */
+        struct list_head pending_master_completion[2];
+        struct list_head pending_completion[2];
+
+        /* use checksums for *this* resync */
+        bool use_csums;
         /* blocks to resync in this run [unit BM_BLOCK_SIZE] */
         unsigned long rs_total;
         /* number of resync blocks that failed in this run */
@@ -788,9 +941,7 @@ struct drbd_device {
         atomic_t pp_in_use;             /* allocated from page pool */
         atomic_t pp_in_use_by_net;      /* sendpage()d, still referenced by tcp */
         wait_queue_head_t ee_wait;
-        struct page *md_io_page;        /* one page buffer for md_io */
         struct drbd_md_io md_io;
-        atomic_t md_io_in_use;          /* protects the md_io, md_io_page and md_io_tmpp */
         spinlock_t al_lock;
         wait_queue_head_t al_wait;
         struct lru_cache *act_log;      /* activity log */
@@ -800,7 +951,6 @@ struct drbd_device {
         atomic_t packet_seq;
         unsigned int peer_seq;
         spinlock_t peer_seq_lock;
-        unsigned int minor;
         unsigned long comm_bm_set; /* communicated number of set bits. */
         struct bm_io_work bm_io_work;
         u64 ed_uuid; /* UUID of the exposed data */
@@ -824,6 +974,21 @@ struct drbd_device {
         struct submit_worker submit;
 };
 
+struct drbd_bm_aio_ctx {
+        struct drbd_device *device;
+        struct list_head list; /* on device->pending_bitmap_io */;
+        unsigned long start_jif;
+        atomic_t in_flight;
+        unsigned int done;
+        unsigned flags;
+#define BM_AIO_COPY_PAGES       1
+#define BM_AIO_WRITE_HINTED     2
+#define BM_AIO_WRITE_ALL_PAGES  4
+#define BM_AIO_READ             8
+        int error;
+        struct kref kref;
+};
+
 struct drbd_config_context {
         /* assigned from drbd_genlmsghdr */
         unsigned int minor;
@@ -949,7 +1114,7 @@ extern int drbd_send_ov_request(struct drbd_peer_device *, sector_t sector, int
 extern int drbd_send_bitmap(struct drbd_device *device);
 extern void drbd_send_sr_reply(struct drbd_peer_device *, enum drbd_state_rv retcode);
 extern void conn_send_sr_reply(struct drbd_connection *connection, enum drbd_state_rv retcode);
-extern void drbd_free_bc(struct drbd_backing_dev *ldev);
+extern void drbd_free_ldev(struct drbd_backing_dev *ldev);
 extern void drbd_device_cleanup(struct drbd_device *device);
 void drbd_print_uuids(struct drbd_device *device, const char *text);
 
@@ -966,13 +1131,7 @@ extern void __drbd_uuid_set(struct drbd_device *device, int idx, u64 val) __must
 extern void drbd_md_set_flag(struct drbd_device *device, int flags) __must_hold(local);
 extern void drbd_md_clear_flag(struct drbd_device *device, int flags)__must_hold(local);
 extern int drbd_md_test_flag(struct drbd_backing_dev *, int);
-#ifndef DRBD_DEBUG_MD_SYNC
 extern void drbd_md_mark_dirty(struct drbd_device *device);
-#else
-#define drbd_md_mark_dirty(m)   drbd_md_mark_dirty_(m, __LINE__ , __func__ )
-extern void drbd_md_mark_dirty_(struct drbd_device *device,
-                unsigned int line, const char *func);
-#endif
 extern void drbd_queue_bitmap_io(struct drbd_device *device,
                                  int (*io_fn)(struct drbd_device *),
                                  void (*done)(struct drbd_device *, int),
@@ -983,9 +1142,8 @@ extern int drbd_bitmap_io(struct drbd_device *device,
 extern int drbd_bitmap_io_from_worker(struct drbd_device *device,
                 int (*io_fn)(struct drbd_device *),
                 char *why, enum bm_flag flags);
-extern int drbd_bmio_set_n_write(struct drbd_device *device);
-extern int drbd_bmio_clear_n_write(struct drbd_device *device);
-extern void drbd_ldev_destroy(struct drbd_device *device);
+extern int drbd_bmio_set_n_write(struct drbd_device *device) __must_hold(local);
+extern int drbd_bmio_clear_n_write(struct drbd_device *device) __must_hold(local);
 
 /* Meta data layout
  *
@@ -1105,17 +1263,21 @@ struct bm_extent {
 /* in which _bitmap_ extent (resp. sector) the bit for a certain
  * _storage_ sector is located in */
 #define BM_SECT_TO_EXT(x)   ((x)>>(BM_EXT_SHIFT-9))
+#define BM_BIT_TO_EXT(x)    ((x) >> (BM_EXT_SHIFT - BM_BLOCK_SHIFT))
 
-/* how much _storage_ sectors we have per bitmap sector */
+/* first storage sector a bitmap extent corresponds to */
 #define BM_EXT_TO_SECT(x)   ((sector_t)(x) << (BM_EXT_SHIFT-9))
+/* how much _storage_ sectors we have per bitmap extent */
 #define BM_SECT_PER_EXT     BM_EXT_TO_SECT(1)
+/* how many bits are covered by one bitmap extent (resync extent) */
+#define BM_BITS_PER_EXT     (1UL << (BM_EXT_SHIFT - BM_BLOCK_SHIFT))
+
+#define BM_BLOCKS_PER_BM_EXT_MASK  (BM_BITS_PER_EXT - 1)
+
 
 /* in one sector of the bitmap, we have this many activity_log extents. */
 #define AL_EXT_PER_BM_SECT  (1 << (BM_EXT_SHIFT - AL_EXTENT_SHIFT))
 
-#define BM_BLOCKS_PER_BM_EXT_B (BM_EXT_SHIFT - BM_BLOCK_SHIFT)
-#define BM_BLOCKS_PER_BM_EXT_MASK  ((1<<BM_BLOCKS_PER_BM_EXT_B) - 1)
-
 /* the extent in "PER_EXTENT" below is an activity log extent
  * we need that many (long words/bytes) to store the bitmap
  *                   of one AL_EXTENT_SIZE chunk of storage.
@@ -1195,11 +1357,11 @@ extern void _drbd_bm_set_bits(struct drbd_device *device,
                 const unsigned long s, const unsigned long e);
 extern int  drbd_bm_test_bit(struct drbd_device *device, unsigned long bitnr);
 extern int  drbd_bm_e_weight(struct drbd_device *device, unsigned long enr);
-extern int  drbd_bm_write_page(struct drbd_device *device, unsigned int idx) __must_hold(local);
 extern int  drbd_bm_read(struct drbd_device *device) __must_hold(local);
 extern void drbd_bm_mark_for_writeout(struct drbd_device *device, int page_nr);
 extern int  drbd_bm_write(struct drbd_device *device) __must_hold(local);
 extern int  drbd_bm_write_hinted(struct drbd_device *device) __must_hold(local);
+extern int  drbd_bm_write_lazy(struct drbd_device *device, unsigned upper_idx) __must_hold(local);
 extern int drbd_bm_write_all(struct drbd_device *device) __must_hold(local);
 extern int  drbd_bm_write_copy_pages(struct drbd_device *device) __must_hold(local);
 extern size_t        drbd_bm_words(struct drbd_device *device);
@@ -1213,7 +1375,6 @@ extern unsigned long _drbd_bm_find_next(struct drbd_device *device, unsigned lon
 extern unsigned long _drbd_bm_find_next_zero(struct drbd_device *device, unsigned long bm_fo);
 extern unsigned long _drbd_bm_total_weight(struct drbd_device *device);
 extern unsigned long drbd_bm_total_weight(struct drbd_device *device);
-extern int drbd_bm_rs_done(struct drbd_device *device);
 /* for receive_bitmap */
 extern void drbd_bm_merge_lel(struct drbd_device *device, size_t offset,
                 size_t number, unsigned long *buffer);
@@ -1312,7 +1473,7 @@ enum determine_dev_size {
 extern enum determine_dev_size
 drbd_determine_dev_size(struct drbd_device *, enum dds_flags, struct resize_parms *) __must_hold(local);
 extern void resync_after_online_grow(struct drbd_device *);
-extern void drbd_reconsider_max_bio_size(struct drbd_device *device);
+extern void drbd_reconsider_max_bio_size(struct drbd_device *device, struct drbd_backing_dev *bdev);
 extern enum drbd_state_rv drbd_set_role(struct drbd_device *device,
                                         enum drbd_role new_role,
                                         int force);
@@ -1333,7 +1494,7 @@ extern void resume_next_sg(struct drbd_device *device);
 extern void suspend_other_sg(struct drbd_device *device);
 extern int drbd_resync_finished(struct drbd_device *device);
 /* maybe rather drbd_main.c ? */
-extern void *drbd_md_get_buffer(struct drbd_device *device);
+extern void *drbd_md_get_buffer(struct drbd_device *device, const char *intent);
 extern void drbd_md_put_buffer(struct drbd_device *device);
 extern int drbd_md_sync_page_io(struct drbd_device *device,
                 struct drbd_backing_dev *bdev, sector_t sector, int rw);
@@ -1380,7 +1541,8 @@ extern void drbd_endio_write_sec_final(struct drbd_peer_request *peer_req);
 extern int drbd_receiver(struct drbd_thread *thi);
 extern int drbd_asender(struct drbd_thread *thi);
 extern bool drbd_rs_c_min_rate_throttle(struct drbd_device *device);
-extern bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector);
+extern bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector,
+                bool throttle_if_app_is_waiting);
 extern int drbd_submit_peer_request(struct drbd_device *,
                                     struct drbd_peer_request *, const unsigned,
                                     const int);
@@ -1464,10 +1626,7 @@ static inline void drbd_generic_make_request(struct drbd_device *device,
 {
         __release(local);
         if (!bio->bi_bdev) {
-                printk(KERN_ERR "drbd%d: drbd_generic_make_request: "
-                                "bio->bi_bdev == NULL\n",
-                       device_to_minor(device));
-                dump_stack();
+                drbd_err(device, "drbd_generic_make_request: bio->bi_bdev == NULL\n");
                 bio_endio(bio, -ENODEV);
                 return;
         }
@@ -1478,7 +1637,8 @@ static inline void drbd_generic_make_request(struct drbd_device *device,
                 generic_make_request(bio);
 }
 
-void drbd_bump_write_ordering(struct drbd_connection *connection, enum write_ordering_e wo);
+void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backing_dev *bdev,
+                              enum write_ordering_e wo);
 
 /* drbd_proc.c */
 extern struct proc_dir_entry *drbd_proc;
@@ -1489,9 +1649,9 @@ extern const char *drbd_role_str(enum drbd_role s);
 /* drbd_actlog.c */
 extern bool drbd_al_begin_io_prepare(struct drbd_device *device, struct drbd_interval *i);
 extern int drbd_al_begin_io_nonblock(struct drbd_device *device, struct drbd_interval *i);
-extern void drbd_al_begin_io_commit(struct drbd_device *device, bool delegate);
+extern void drbd_al_begin_io_commit(struct drbd_device *device);
 extern bool drbd_al_begin_io_fastpath(struct drbd_device *device, struct drbd_interval *i);
-extern void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i, bool delegate);
+extern void drbd_al_begin_io(struct drbd_device *device, struct drbd_interval *i);
 extern void drbd_al_complete_io(struct drbd_device *device, struct drbd_interval *i);
 extern void drbd_rs_complete_io(struct drbd_device *device, sector_t sector);
 extern int drbd_rs_begin_io(struct drbd_device *device, sector_t sector);
@@ -1501,14 +1661,17 @@ extern int drbd_rs_del_all(struct drbd_device *device);
 extern void drbd_rs_failed_io(struct drbd_device *device,
                 sector_t sector, int size);
 extern void drbd_advance_rs_marks(struct drbd_device *device, unsigned long still_to_go);
-extern void __drbd_set_in_sync(struct drbd_device *device, sector_t sector,
-                int size, const char *file, const unsigned int line);
+
+enum update_sync_bits_mode { RECORD_RS_FAILED, SET_OUT_OF_SYNC, SET_IN_SYNC };
+extern int __drbd_change_sync(struct drbd_device *device, sector_t sector, int size,
+                enum update_sync_bits_mode mode,
+                const char *file, const unsigned int line);
 #define drbd_set_in_sync(device, sector, size) \
-        __drbd_set_in_sync(device, sector, size, __FILE__, __LINE__)
-extern int __drbd_set_out_of_sync(struct drbd_device *device, sector_t sector,
-                int size, const char *file, const unsigned int line);
+        __drbd_change_sync(device, sector, size, SET_IN_SYNC, __FILE__, __LINE__)
 #define drbd_set_out_of_sync(device, sector, size) \
-        __drbd_set_out_of_sync(device, sector, size, __FILE__, __LINE__)
+        __drbd_change_sync(device, sector, size, SET_OUT_OF_SYNC, __FILE__, __LINE__)
+#define drbd_rs_failed_io(device, sector, size) \
+        __drbd_change_sync(device, sector, size, RECORD_RS_FAILED, __FILE__, __LINE__)
 extern void drbd_al_shrink(struct drbd_device *device);
 extern int drbd_initialize_al(struct drbd_device *, void *);
 
@@ -1764,25 +1927,38 @@ static inline sector_t drbd_md_ss(struct drbd_backing_dev *bdev)
 }
 
 static inline void
-drbd_queue_work_front(struct drbd_work_queue *q, struct drbd_work *w)
+drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
 {
         unsigned long flags;
         spin_lock_irqsave(&q->q_lock, flags);
-        list_add(&w->list, &q->q);
+        list_add_tail(&w->list, &q->q);
         spin_unlock_irqrestore(&q->q_lock, flags);
         wake_up(&q->q_wait);
 }
 
 static inline void
-drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
+drbd_queue_work_if_unqueued(struct drbd_work_queue *q, struct drbd_work *w)
 {
         unsigned long flags;
         spin_lock_irqsave(&q->q_lock, flags);
-        list_add_tail(&w->list, &q->q);
+        if (list_empty_careful(&w->list))
+                list_add_tail(&w->list, &q->q);
         spin_unlock_irqrestore(&q->q_lock, flags);
         wake_up(&q->q_wait);
 }
 
+static inline void
+drbd_device_post_work(struct drbd_device *device, int work_bit)
+{
+        if (!test_and_set_bit(work_bit, &device->flags)) {
+                struct drbd_connection *connection =
+                        first_peer_device(device)->connection;
+                struct drbd_work_queue *q = &connection->sender_work;
+                if (!test_and_set_bit(DEVICE_WORK_PENDING, &connection->flags))
+                        wake_up(&q->q_wait);
+        }
+}
+
 extern void drbd_flush_workqueue(struct drbd_work_queue *work_queue);
 
 static inline void wake_asender(struct drbd_connection *connection)
@@ -1859,7 +2035,7 @@ static inline void inc_ap_pending(struct drbd_device *device)
                         func, line,                                     \
                         atomic_read(&device->which))
 
-#define dec_ap_pending(device) _dec_ap_pending(device, __FUNCTION__, __LINE__)
+#define dec_ap_pending(device) _dec_ap_pending(device, __func__, __LINE__)
 static inline void _dec_ap_pending(struct drbd_device *device, const char *func, int line)
 {
         if (atomic_dec_and_test(&device->ap_pending_cnt))
@@ -1878,7 +2054,7 @@ static inline void inc_rs_pending(struct drbd_device *device)
         atomic_inc(&device->rs_pending_cnt);
 }
 
-#define dec_rs_pending(device) _dec_rs_pending(device, __FUNCTION__, __LINE__)
+#define dec_rs_pending(device) _dec_rs_pending(device, __func__, __LINE__)
 static inline void _dec_rs_pending(struct drbd_device *device, const char *func, int line)
 {
         atomic_dec(&device->rs_pending_cnt);
@@ -1899,20 +2075,29 @@ static inline void inc_unacked(struct drbd_device *device)
         atomic_inc(&device->unacked_cnt);
 }
 
-#define dec_unacked(device) _dec_unacked(device, __FUNCTION__, __LINE__)
+#define dec_unacked(device) _dec_unacked(device, __func__, __LINE__)
 static inline void _dec_unacked(struct drbd_device *device, const char *func, int line)
 {
         atomic_dec(&device->unacked_cnt);
         ERR_IF_CNT_IS_NEGATIVE(unacked_cnt, func, line);
 }
 
-#define sub_unacked(device, n) _sub_unacked(device, n, __FUNCTION__, __LINE__)
+#define sub_unacked(device, n) _sub_unacked(device, n, __func__, __LINE__)
 static inline void _sub_unacked(struct drbd_device *device, int n, const char *func, int line)
 {
         atomic_sub(n, &device->unacked_cnt);
         ERR_IF_CNT_IS_NEGATIVE(unacked_cnt, func, line);
 }
 
+static inline bool is_sync_state(enum drbd_conns connection_state)
+{
+        return
+           (connection_state == C_SYNC_SOURCE
+        ||  connection_state == C_SYNC_TARGET
+        ||  connection_state == C_PAUSED_SYNC_S
+        ||  connection_state == C_PAUSED_SYNC_T);
+}
+
 /**
  * get_ldev() - Increase the ref count on device->ldev. Returns 0 if there is no ldev
  * @M:          DRBD device.
@@ -1924,6 +2109,11 @@ static inline void _sub_unacked(struct drbd_device *device, int n, const char *f
 
 static inline void put_ldev(struct drbd_device *device)
 {
+        enum drbd_disk_state ds = device->state.disk;
+        /* We must check the state *before* the atomic_dec becomes visible,
+         * or we have a theoretical race where someone hitting zero,
+         * while state still D_FAILED, will then see D_DISKLESS in the
+         * condition below and calling into destroy, where he must not, yet. */
         int i = atomic_dec_return(&device->local_cnt);
 
         /* This may be called from some endio handler,
@@ -1932,15 +2122,13 @@ static inline void put_ldev(struct drbd_device *device)
         __release(local);
         D_ASSERT(device, i >= 0);
         if (i == 0) {
-                if (device->state.disk == D_DISKLESS)
+                if (ds == D_DISKLESS)
                         /* even internal references gone, safe to destroy */
-                        drbd_ldev_destroy(device);
-                if (device->state.disk == D_FAILED) {
+                        drbd_device_post_work(device, DESTROY_DISK);
+                if (ds == D_FAILED)
                         /* all application IO references gone. */
-                        if (!test_and_set_bit(GO_DISKLESS, &device->flags))
-                                drbd_queue_work(&first_peer_device(device)->connection->sender_work,
-                                                &device->go_diskless);
-                }
+                        if (!test_and_set_bit(GOING_DISKLESS, &device->flags))
+                                drbd_device_post_work(device, GO_DISKLESS);
                 wake_up(&device->misc_wait);
         }
 }
@@ -1964,54 +2152,6 @@ static inline int _get_ldev_if_state(struct drbd_device *device, enum drbd_disk_
 extern int _get_ldev_if_state(struct drbd_device *device, enum drbd_disk_state mins);
 #endif
 
-/* you must have an "get_ldev" reference */
-static inline void drbd_get_syncer_progress(struct drbd_device *device,
-                unsigned long *bits_left, unsigned int *per_mil_done)
-{
-        /* this is to break it at compile time when we change that, in case we
-         * want to support more than (1<<32) bits on a 32bit arch. */
-        typecheck(unsigned long, device->rs_total);
-
-        /* note: both rs_total and rs_left are in bits, i.e. in
-         * units of BM_BLOCK_SIZE.
-         * for the percentage, we don't care. */
-
-        if (device->state.conn == C_VERIFY_S || device->state.conn == C_VERIFY_T)
-                *bits_left = device->ov_left;
-        else
-                *bits_left = drbd_bm_total_weight(device) - device->rs_failed;
-        /* >> 10 to prevent overflow,
-         * +1 to prevent division by zero */
-        if (*bits_left > device->rs_total) {
-                /* doh. maybe a logic bug somewhere.
-                 * may also be just a race condition
-                 * between this and a disconnect during sync.
-                 * for now, just prevent in-kernel buffer overflow.
-                 */
-                smp_rmb();
-                drbd_warn(device, "cs:%s rs_left=%lu > rs_total=%lu (rs_failed %lu)\n",
-                                drbd_conn_str(device->state.conn),
-                                *bits_left, device->rs_total, device->rs_failed);
-                *per_mil_done = 0;
-        } else {
-                /* Make sure the division happens in long context.
-                 * We allow up to one petabyte storage right now,
-                 * at a granularity of 4k per bit that is 2**38 bits.
-                 * After shift right and multiplication by 1000,
-                 * this should still fit easily into a 32bit long,
-                 * so we don't need a 64bit division on 32bit arch.
-                 * Note: currently we don't support such large bitmaps on 32bit
-                 * arch anyways, but no harm done to be prepared for it here.
-                 */
-                unsigned int shift = device->rs_total > UINT_MAX ? 16 : 10;
-                unsigned long left = *bits_left >> shift;
-                unsigned long total = 1UL + (device->rs_total >> shift);
-                unsigned long tmp = 1000UL - left * 1000UL/total;
-                *per_mil_done = tmp;
-        }
-}
-
-
 /* this throttles on-the-fly application requests
  * according to max_buffers settings;
  * maybe re-implement using semaphores? */
@@ -2201,25 +2341,6 @@ static inline int drbd_queue_order_type(struct drbd_device *device)
         return QUEUE_ORDERED_NONE;
 }
 
-static inline void drbd_md_flush(struct drbd_device *device)
-{
-        int r;
-
-        if (device->ldev == NULL) {
-                drbd_warn(device, "device->ldev == NULL in drbd_md_flush\n");
-                return;
-        }
-
-        if (test_bit(MD_NO_FUA, &device->flags))
-                return;
-
-        r = blkdev_issue_flush(device->ldev->md_bdev, GFP_NOIO, NULL);
-        if (r) {
-                set_bit(MD_NO_FUA, &device->flags);
-                drbd_err(device, "meta data flush failed with status %d, disabling md-flushes\n", r);
-        }
-}
-
 static inline struct drbd_connection *first_connection(struct drbd_resource *resource)
 {
         return list_first_entry_or_null(&resource->connections,
diff --git a/drivers/block/drbd/drbd_interval.h b/drivers/block/drbd/drbd_interval.h
index f38fcb00c10d..f210543f05f4 100644
--- a/drivers/block/drbd/drbd_interval.h
+++ b/drivers/block/drbd/drbd_interval.h
@@ -10,7 +10,9 @@ struct drbd_interval {
         unsigned int size;      /* size in bytes */
         sector_t end;           /* highest interval end in subtree */
         int local:1             /* local or remote request? */;
-        int waiting:1;
+        int waiting:1;          /* someone is waiting for this to complete */
+        int completed:1;        /* this has been completed already;
+                                 * ignore for conflict detection */
 };
 
 static inline void drbd_clear_interval(struct drbd_interval *i)
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 960645c26e6f..9b465bb68487 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -26,7 +26,10 @@
 
  */
 
+#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
+
 #include <linux/module.h>
+#include <linux/jiffies.h>
 #include <linux/drbd.h>
 #include <asm/uaccess.h>
 #include <asm/types.h>
@@ -54,16 +57,14 @@
 #include "drbd_int.h"
 #include "drbd_protocol.h"
 #include "drbd_req.h" /* only for _req_mod in tl_release and tl_clear */
-
 #include "drbd_vli.h"
+#include "drbd_debugfs.h"
 
 static DEFINE_MUTEX(drbd_main_mutex);
 static int drbd_open(struct block_device *bdev, fmode_t mode);
 static void drbd_release(struct gendisk *gd, fmode_t mode);
-static int w_md_sync(struct drbd_work *w, int unused);
 static void md_sync_timer_fn(unsigned long data);
 static int w_bitmap_io(struct drbd_work *w, int unused);
-static int w_go_diskless(struct drbd_work *w, int unused);
 
 MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
               "Lars Ellenberg <lars@linbit.com>");
@@ -264,7 +265,7 @@ bail:
 
 /**
  * _tl_restart() - Walks the transfer log, and applies an action to all requests
- * @device:     DRBD device.
+ * @connection: DRBD connection to operate on.
  * @what:       The action/event to perform with all request objects
  *
  * @what might be one of CONNECTION_LOST_WHILE_PENDING, RESEND, FAIL_FROZEN_DISK_IO,
@@ -662,6 +663,11 @@ static int __send_command(struct drbd_connection *connection, int vnr,
                             msg_flags);
         if (data && !err)
                 err = drbd_send_all(connection, sock->socket, data, size, 0);
+        /* DRBD protocol "pings" are latency critical.
+         * This is supposed to trigger tcp_push_pending_frames() */
+        if (!err && (cmd == P_PING || cmd == P_PING_ACK))
+                drbd_tcp_nodelay(sock->socket);
+
         return err;
 }
 
@@ -1636,7 +1642,10 @@ int drbd_send_dblock(struct drbd_peer_device *peer_device, struct drbd_request *
         if (peer_device->connection->agreed_pro_version >= 100) {
                 if (req->rq_state & RQ_EXP_RECEIVE_ACK)
                         dp_flags |= DP_SEND_RECEIVE_ACK;
-                if (req->rq_state & RQ_EXP_WRITE_ACK)
+                /* During resync, request an explicit write ack,
+                 * even in protocol != C */
+                if (req->rq_state & RQ_EXP_WRITE_ACK
+                || (dp_flags & DP_MAY_SET_IN_SYNC))
                         dp_flags |= DP_SEND_WRITE_ACK;
         }
         p->dp_flags = cpu_to_be32(dp_flags);
@@ -1900,6 +1909,7 @@ void drbd_init_set_defaults(struct drbd_device *device)
         drbd_set_defaults(device);
 
         atomic_set(&device->ap_bio_cnt, 0);
+        atomic_set(&device->ap_actlog_cnt, 0);
         atomic_set(&device->ap_pending_cnt, 0);
         atomic_set(&device->rs_pending_cnt, 0);
         atomic_set(&device->unacked_cnt, 0);
@@ -1908,7 +1918,7 @@ void drbd_init_set_defaults(struct drbd_device *device)
         atomic_set(&device->rs_sect_in, 0);
         atomic_set(&device->rs_sect_ev, 0);
         atomic_set(&device->ap_in_flight, 0);
-        atomic_set(&device->md_io_in_use, 0);
+        atomic_set(&device->md_io.in_use, 0);
 
         mutex_init(&device->own_state_mutex);
         device->state_mutex = &device->own_state_mutex;
@@ -1924,17 +1934,15 @@ void drbd_init_set_defaults(struct drbd_device *device)
         INIT_LIST_HEAD(&device->resync_reads);
         INIT_LIST_HEAD(&device->resync_work.list);
         INIT_LIST_HEAD(&device->unplug_work.list);
-        INIT_LIST_HEAD(&device->go_diskless.list);
-        INIT_LIST_HEAD(&device->md_sync_work.list);
-        INIT_LIST_HEAD(&device->start_resync_work.list);
         INIT_LIST_HEAD(&device->bm_io_work.w.list);
+        INIT_LIST_HEAD(&device->pending_master_completion[0]);
+        INIT_LIST_HEAD(&device->pending_master_completion[1]);
+        INIT_LIST_HEAD(&device->pending_completion[0]);
+        INIT_LIST_HEAD(&device->pending_completion[1]);
 
         device->resync_work.cb  = w_resync_timer;
         device->unplug_work.cb  = w_send_write_hint;
-        device->go_diskless.cb  = w_go_diskless;
-        device->md_sync_work.cb = w_md_sync;
         device->bm_io_work.w.cb = w_bitmap_io;
-        device->start_resync_work.cb = w_start_resync;
 
         init_timer(&device->resync_timer);
         init_timer(&device->md_sync_timer);
@@ -1992,7 +2000,7 @@ void drbd_device_cleanup(struct drbd_device *device)
                 drbd_bm_cleanup(device);
         }
 
-        drbd_free_bc(device->ldev);
+        drbd_free_ldev(device->ldev);
         device->ldev = NULL;
 
         clear_bit(AL_SUSPENDED, &device->flags);
@@ -2006,7 +2014,6 @@ void drbd_device_cleanup(struct drbd_device *device)
         D_ASSERT(device, list_empty(&first_peer_device(device)->connection->sender_work.q));
         D_ASSERT(device, list_empty(&device->resync_work.list));
         D_ASSERT(device, list_empty(&device->unplug_work.list));
-        D_ASSERT(device, list_empty(&device->go_diskless.list));
 
         drbd_set_defaults(device);
 }
@@ -2129,20 +2136,6 @@ Enomem:
         return -ENOMEM;
 }
 
-static int drbd_notify_sys(struct notifier_block *this, unsigned long code,
-        void *unused)
-{
-        /* just so we have it.  you never know what interesting things we
-         * might want to do here some day...
-         */
-
-        return NOTIFY_DONE;
-}
-
-static struct notifier_block drbd_notifier = {
-        .notifier_call = drbd_notify_sys,
-};
-
 static void drbd_release_all_peer_reqs(struct drbd_device *device)
 {
         int rr;
@@ -2173,7 +2166,7 @@ void drbd_destroy_device(struct kref *kref)
 {
         struct drbd_device *device = container_of(kref, struct drbd_device, kref);
         struct drbd_resource *resource = device->resource;
-        struct drbd_connection *connection;
+        struct drbd_peer_device *peer_device, *tmp_peer_device;
 
         del_timer_sync(&device->request_timer);
 
@@ -2187,7 +2180,7 @@ void drbd_destroy_device(struct kref *kref)
         if (device->this_bdev)
                 bdput(device->this_bdev);
 
-        drbd_free_bc(device->ldev);
+        drbd_free_ldev(device->ldev);
         device->ldev = NULL;
 
         drbd_release_all_peer_reqs(device);
@@ -2200,15 +2193,20 @@ void drbd_destroy_device(struct kref *kref)
 
         if (device->bitmap) /* should no longer be there. */
                 drbd_bm_cleanup(device);
-        __free_page(device->md_io_page);
+        __free_page(device->md_io.page);
         put_disk(device->vdisk);
         blk_cleanup_queue(device->rq_queue);
         kfree(device->rs_plan_s);
-        kfree(first_peer_device(device));
-        kfree(device);
 
-        for_each_connection(connection, resource)
-                kref_put(&connection->kref, drbd_destroy_connection);
+        /* not for_each_connection(connection, resource):
+         * those may have been cleaned up and disassociated already.
+         */
+        for_each_peer_device_safe(peer_device, tmp_peer_device, device) {
+                kref_put(&peer_device->connection->kref, drbd_destroy_connection);
+                kfree(peer_device);
+        }
+        memset(device, 0xfd, sizeof(*device));
+        kfree(device);
         kref_put(&resource->kref, drbd_destroy_resource);
 }
 
@@ -2236,7 +2234,7 @@ static void do_retry(struct work_struct *ws)
         list_for_each_entry_safe(req, tmp, &writes, tl_requests) {
                 struct drbd_device *device = req->device;
                 struct bio *bio = req->master_bio;
-                unsigned long start_time = req->start_time;
+                unsigned long start_jif = req->start_jif;
                 bool expected;
 
                 expected =
@@ -2271,10 +2269,12 @@ static void do_retry(struct work_struct *ws)
                 /* We are not just doing generic_make_request(),
                  * as we want to keep the start_time information. */
                 inc_ap_bio(device);
-                __drbd_make_request(device, bio, start_time);
+                __drbd_make_request(device, bio, start_jif);
         }
 }
 
+/* called via drbd_req_put_completion_ref(),
+ * holds resource->req_lock */
 void drbd_restart_request(struct drbd_request *req)
 {
         unsigned long flags;
@@ -2298,6 +2298,7 @@ void drbd_destroy_resource(struct kref *kref)
         idr_destroy(&resource->devices);
         free_cpumask_var(resource->cpu_mask);
         kfree(resource->name);
+        memset(resource, 0xf2, sizeof(*resource));
         kfree(resource);
 }
 
@@ -2307,8 +2308,10 @@ void drbd_free_resource(struct drbd_resource *resource)
 
         for_each_connection_safe(connection, tmp, resource) {
                 list_del(&connection->connections);
+                drbd_debugfs_connection_cleanup(connection);
                 kref_put(&connection->kref, drbd_destroy_connection);
         }
+        drbd_debugfs_resource_cleanup(resource);
         kref_put(&resource->kref, drbd_destroy_resource);
 }
 
@@ -2318,8 +2321,6 @@ static void drbd_cleanup(void)
         struct drbd_device *device;
         struct drbd_resource *resource, *tmp;
 
-        unregister_reboot_notifier(&drbd_notifier);
-
         /* first remove proc,
          * drbdsetup uses it's presence to detect
          * whether DRBD is loaded.
@@ -2335,6 +2336,7 @@ static void drbd_cleanup(void)
                 destroy_workqueue(retry.wq);
 
         drbd_genl_unregister();
+        drbd_debugfs_cleanup();
 
         idr_for_each_entry(&drbd_devices, device, i)
                 drbd_delete_device(device);
@@ -2350,7 +2352,7 @@ static void drbd_cleanup(void)
 
         idr_destroy(&drbd_devices);
 
-        printk(KERN_INFO "drbd: module cleanup done.\n");
+        pr_info("module cleanup done.\n");
 }
 
 /**
@@ -2539,6 +2541,20 @@ int set_resource_options(struct drbd_resource *resource, struct res_opts *res_op
         if (nr_cpu_ids > 1 && res_opts->cpu_mask[0] != 0) {
                 err = bitmap_parse(res_opts->cpu_mask, DRBD_CPU_MASK_SIZE,
                                    cpumask_bits(new_cpu_mask), nr_cpu_ids);
+                if (err == -EOVERFLOW) {
+                        /* So what. mask it out. */
+                        cpumask_var_t tmp_cpu_mask;
+                        if (zalloc_cpumask_var(&tmp_cpu_mask, GFP_KERNEL)) {
+                                cpumask_setall(tmp_cpu_mask);
+                                cpumask_and(new_cpu_mask, new_cpu_mask, tmp_cpu_mask);
+                                drbd_warn(resource, "Overflow in bitmap_parse(%.12s%s), truncating to %u bits\n",
+                                        res_opts->cpu_mask,
+                                        strlen(res_opts->cpu_mask) > 12 ? "..." : "",
+                                        nr_cpu_ids);
+                                free_cpumask_var(tmp_cpu_mask);
+                                err = 0;
+                        }
+                }
                 if (err) {
                         drbd_warn(resource, "bitmap_parse() failed with %d\n", err);
                         /* retcode = ERR_CPU_MASK_PARSE; */
@@ -2579,10 +2595,12 @@ struct drbd_resource *drbd_create_resource(const char *name)
         kref_init(&resource->kref);
         idr_init(&resource->devices);
         INIT_LIST_HEAD(&resource->connections);
+        resource->write_ordering = WO_bdev_flush;
         list_add_tail_rcu(&resource->resources, &drbd_resources);
         mutex_init(&resource->conf_update);
         mutex_init(&resource->adm_mutex);
         spin_lock_init(&resource->req_lock);
+        drbd_debugfs_resource_add(resource);
         return resource;
 
 fail_free_name:
@@ -2593,7 +2611,7 @@ fail:
         return NULL;
 }
 
-/* caller must be under genl_lock() */
+/* caller must be under adm_mutex */
 struct drbd_connection *conn_create(const char *name, struct res_opts *res_opts)
 {
         struct drbd_resource *resource;
@@ -2617,7 +2635,6 @@ struct drbd_connection *conn_create(const char *name, struct res_opts *res_opts)
         INIT_LIST_HEAD(&connection->current_epoch->list);
         connection->epochs = 1;
         spin_lock_init(&connection->epoch_lock);
-        connection->write_ordering = WO_bdev_flush;
 
         connection->send.seen_any_write_yet = false;
         connection->send.current_epoch_nr = 0;
@@ -2652,6 +2669,7 @@ struct drbd_connection *conn_create(const char *name, struct res_opts *res_opts)
 
         kref_get(&resource->kref);
         list_add_tail_rcu(&connection->connections, &resource->connections);
+        drbd_debugfs_connection_add(connection);
         return connection;
 
 fail_resource:
@@ -2680,6 +2698,7 @@ void drbd_destroy_connection(struct kref *kref)
         drbd_free_socket(&connection->data);
         kfree(connection->int_dig_in);
         kfree(connection->int_dig_vv);
+        memset(connection, 0xfc, sizeof(*connection));
         kfree(connection);
         kref_put(&resource->kref, drbd_destroy_resource);
 }
@@ -2694,7 +2713,6 @@ static int init_submitter(struct drbd_device *device)
                 return -ENOMEM;
 
         INIT_WORK(&device->submit.worker, do_submit);
-        spin_lock_init(&device->submit.lock);
         INIT_LIST_HEAD(&device->submit.writes);
         return 0;
 }
@@ -2764,8 +2782,8 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
         blk_queue_merge_bvec(q, drbd_merge_bvec);
         q->queue_lock = &resource->req_lock;
 
-        device->md_io_page = alloc_page(GFP_KERNEL);
-        if (!device->md_io_page)
+        device->md_io.page = alloc_page(GFP_KERNEL);
+        if (!device->md_io.page)
                 goto out_no_io_page;
 
         if (drbd_bm_init(device))
@@ -2794,6 +2812,7 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
         kref_get(&device->kref);
 
         INIT_LIST_HEAD(&device->peer_devices);
+        INIT_LIST_HEAD(&device->pending_bitmap_io);
         for_each_connection(connection, resource) {
                 peer_device = kzalloc(sizeof(struct drbd_peer_device), GFP_KERNEL);
                 if (!peer_device)
@@ -2829,7 +2848,10 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
                 for_each_peer_device(peer_device, device)
                         drbd_connected(peer_device);
         }
-
+        /* move to create_peer_device() */
+        for_each_peer_device(peer_device, device)
+                drbd_debugfs_peer_device_add(peer_device);
+        drbd_debugfs_device_add(device);
         return NO_ERROR;
 
 out_idr_remove_vol:
@@ -2853,7 +2875,7 @@ out_idr_remove_minor:
 out_no_minor_idr:
         drbd_bm_cleanup(device);
 out_no_bitmap:
-        __free_page(device->md_io_page);
+        __free_page(device->md_io.page);
 out_no_io_page:
         put_disk(disk);
 out_no_disk:
@@ -2868,8 +2890,13 @@ void drbd_delete_device(struct drbd_device *device)
 {
         struct drbd_resource *resource = device->resource;
         struct drbd_connection *connection;
+        struct drbd_peer_device *peer_device;
         int refs = 3;
 
+        /* move to free_peer_device() */
+        for_each_peer_device(peer_device, device)
+                drbd_debugfs_peer_device_cleanup(peer_device);
+        drbd_debugfs_device_cleanup(device);
         for_each_connection(connection, resource) {
                 idr_remove(&connection->peer_devices, device->vnr);
                 refs++;
@@ -2881,13 +2908,12 @@ void drbd_delete_device(struct drbd_device *device)
         kref_sub(&device->kref, refs, drbd_destroy_device);
 }
 
-int __init drbd_init(void)
+static int __init drbd_init(void)
 {
         int err;
 
         if (minor_count < DRBD_MINOR_COUNT_MIN || minor_count > DRBD_MINOR_COUNT_MAX) {
-                printk(KERN_ERR
-                       "drbd: invalid minor_count (%d)\n", minor_count);
+                pr_err("invalid minor_count (%d)\n", minor_count);
 #ifdef MODULE
                 return -EINVAL;
 #else
@@ -2897,14 +2923,11 @@ int __init drbd_init(void)
 
         err = register_blkdev(DRBD_MAJOR, "drbd");
         if (err) {
-                printk(KERN_ERR
-                       "drbd: unable to register block device major %d\n",
+                pr_err("unable to register block device major %d\n",
                        DRBD_MAJOR);
                 return err;
         }
 
-        register_reboot_notifier(&drbd_notifier);
-
         /*
          * allocate all necessary structs
          */
@@ -2918,7 +2941,7 @@ int __init drbd_init(void)
 
         err = drbd_genl_register();
         if (err) {
-                printk(KERN_ERR "drbd: unable to register generic netlink family\n");
+                pr_err("unable to register generic netlink family\n");
                 goto fail;
         }
 
@@ -2929,38 +2952,39 @@ int __init drbd_init(void)
         err = -ENOMEM;
         drbd_proc = proc_create_data("drbd", S_IFREG | S_IRUGO , NULL, &drbd_proc_fops, NULL);
         if (!drbd_proc) {
-                printk(KERN_ERR "drbd: unable to register proc file\n");
+                pr_err("unable to register proc file\n");
                 goto fail;
         }
 
         retry.wq = create_singlethread_workqueue("drbd-reissue");
         if (!retry.wq) {
-                printk(KERN_ERR "drbd: unable to create retry workqueue\n");
+                pr_err("unable to create retry workqueue\n");
                 goto fail;
         }
         INIT_WORK(&retry.worker, do_retry);
         spin_lock_init(&retry.lock);
         INIT_LIST_HEAD(&retry.writes);
 
-        printk(KERN_INFO "drbd: initialized. "
+        if (drbd_debugfs_init())
+                pr_notice("failed to initialize debugfs -- will not be available\n");
+
+        pr_info("initialized. "
                "Version: " REL_VERSION " (api:%d/proto:%d-%d)\n",
                API_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX);
-        printk(KERN_INFO "drbd: %s\n", drbd_buildtag());
-        printk(KERN_INFO "drbd: registered as block device major %d\n",
-                DRBD_MAJOR);
-
+        pr_info("%s\n", drbd_buildtag());
+        pr_info("registered as block device major %d\n", DRBD_MAJOR);
         return 0; /* Success! */
 
 fail:
         drbd_cleanup();
         if (err == -ENOMEM)
-                printk(KERN_ERR "drbd: ran out of memory\n");
+                pr_err("ran out of memory\n");
         else
-                printk(KERN_ERR "drbd: initialization failure\n");
+                pr_err("initialization failure\n");
         return err;
 }
 
-void drbd_free_bc(struct drbd_backing_dev *ldev)
+void drbd_free_ldev(struct drbd_backing_dev *ldev)
 {
         if (ldev == NULL)
                 return;
@@ -2972,24 +2996,29 @@ void drbd_free_bc(struct drbd_backing_dev *ldev)
         kfree(ldev);
 }
 
-void drbd_free_sock(struct drbd_connection *connection)
+static void drbd_free_one_sock(struct drbd_socket *ds)
 {
-        if (connection->data.socket) {
-                mutex_lock(&connection->data.mutex);
-                kernel_sock_shutdown(connection->data.socket, SHUT_RDWR);
-                sock_release(connection->data.socket);
-                connection->data.socket = NULL;
-                mutex_unlock(&connection->data.mutex);
-        }
-        if (connection->meta.socket) {
-                mutex_lock(&connection->meta.mutex);
-                kernel_sock_shutdown(connection->meta.socket, SHUT_RDWR);
-                sock_release(connection->meta.socket);
-                connection->meta.socket = NULL;
-                mutex_unlock(&connection->meta.mutex);
+        struct socket *s;
+        mutex_lock(&ds->mutex);
+        s = ds->socket;
+        ds->socket = NULL;
+        mutex_unlock(&ds->mutex);
+        if (s) {
+                /* so debugfs does not need to mutex_lock() */
+                synchronize_rcu();
+                kernel_sock_shutdown(s, SHUT_RDWR);
+                sock_release(s);
         }
 }
 
+void drbd_free_sock(struct drbd_connection *connection)
+{
+        if (connection->data.socket)
+                drbd_free_one_sock(&connection->data);
+        if (connection->meta.socket)
+                drbd_free_one_sock(&connection->meta);
+}
+
 /* meta data management */
 
 void conn_md_sync(struct drbd_connection *connection)
@@ -3093,7 +3122,7 @@ void drbd_md_sync(struct drbd_device *device)
         if (!get_ldev_if_state(device, D_FAILED))
                 return;
 
-        buffer = drbd_md_get_buffer(device);
+        buffer = drbd_md_get_buffer(device, __func__);
         if (!buffer)
                 goto out;
 
@@ -3253,7 +3282,7 @@ int drbd_md_read(struct drbd_device *device, struct drbd_backing_dev *bdev)
         if (device->state.disk != D_DISKLESS)
                 return ERR_DISK_CONFIGURED;
 
-        buffer = drbd_md_get_buffer(device);
+        buffer = drbd_md_get_buffer(device, __func__);
         if (!buffer)
                 return ERR_NOMEM;
 
@@ -3466,23 +3495,19 @@ void drbd_uuid_set_bm(struct drbd_device *device, u64 val) __must_hold(local)
  *
  * Sets all bits in the bitmap and writes the whole bitmap to stable storage.
  */
-int drbd_bmio_set_n_write(struct drbd_device *device)
+int drbd_bmio_set_n_write(struct drbd_device *device) __must_hold(local)
 {
         int rv = -EIO;
 
-        if (get_ldev_if_state(device, D_ATTACHING)) {
-                drbd_md_set_flag(device, MDF_FULL_SYNC);
-                drbd_md_sync(device);
-                drbd_bm_set_all(device);
-
-                rv = drbd_bm_write(device);
+        drbd_md_set_flag(device, MDF_FULL_SYNC);
+        drbd_md_sync(device);
+        drbd_bm_set_all(device);
 
-                if (!rv) {
-                        drbd_md_clear_flag(device, MDF_FULL_SYNC);
-                        drbd_md_sync(device);
-                }
+        rv = drbd_bm_write(device);
 
-                put_ldev(device);
+        if (!rv) {
+                drbd_md_clear_flag(device, MDF_FULL_SYNC);
+                drbd_md_sync(device);
         }
 
         return rv;
@@ -3494,18 +3519,11 @@ int drbd_bmio_set_n_write(struct drbd_device *device)
  *
  * Clears all bits in the bitmap and writes the whole bitmap to stable storage.
  */
-int drbd_bmio_clear_n_write(struct drbd_device *device)
+int drbd_bmio_clear_n_write(struct drbd_device *device) __must_hold(local)
 {
-        int rv = -EIO;
-
         drbd_resume_al(device);
-        if (get_ldev_if_state(device, D_ATTACHING)) {
-                drbd_bm_clear_all(device);
-                rv = drbd_bm_write(device);
-                put_ldev(device);
-        }
-
-        return rv;
+        drbd_bm_clear_all(device);
+        return drbd_bm_write(device);
 }
 
 static int w_bitmap_io(struct drbd_work *w, int unused)
@@ -3537,61 +3555,6 @@ static int w_bitmap_io(struct drbd_work *w, int unused)
         return 0;
 }
 
-void drbd_ldev_destroy(struct drbd_device *device)
-{
-        lc_destroy(device->resync);
-        device->resync = NULL;
-        lc_destroy(device->act_log);
-        device->act_log = NULL;
-        __no_warn(local,
-                drbd_free_bc(device->ldev);
-                device->ldev = NULL;);
-
-        clear_bit(GO_DISKLESS, &device->flags);
-}
-
-static int w_go_diskless(struct drbd_work *w, int unused)
-{
-        struct drbd_device *device =
-                container_of(w, struct drbd_device, go_diskless);
-
-        D_ASSERT(device, device->state.disk == D_FAILED);
-        /* we cannot assert local_cnt == 0 here, as get_ldev_if_state will
-         * inc/dec it frequently. Once we are D_DISKLESS, no one will touch
-         * the protected members anymore, though, so once put_ldev reaches zero
-         * again, it will be safe to free them. */
-
-        /* Try to write changed bitmap pages, read errors may have just
-         * set some bits outside the area covered by the activity log.
-         *
-         * If we have an IO error during the bitmap writeout,
-         * we will want a full sync next time, just in case.
-         * (Do we want a specific meta data flag for this?)
-         *
-         * If that does not make it to stable storage either,
-         * we cannot do anything about that anymore.
-         *
-         * We still need to check if both bitmap and ldev are present, we may
-         * end up here after a failed attach, before ldev was even assigned.
-         */
-        if (device->bitmap && device->ldev) {
-                /* An interrupted resync or similar is allowed to recounts bits
-                 * while we detach.
-                 * Any modifications would not be expected anymore, though.
-                 */
-                if (drbd_bitmap_io_from_worker(device, drbd_bm_write,
-                                        "detach", BM_LOCKED_TEST_ALLOWED)) {
-                        if (test_bit(WAS_READ_ERROR, &device->flags)) {
-                                drbd_md_set_flag(device, MDF_FULL_SYNC);
-                                drbd_md_sync(device);
-                        }
-                }
-        }
-
-        drbd_force_state(device, NS(disk, D_DISKLESS));
-        return 0;
-}
-
 /**
  * drbd_queue_bitmap_io() - Queues an IO operation on the whole bitmap
  * @device:     DRBD device.
@@ -3603,6 +3566,9 @@ static int w_go_diskless(struct drbd_work *w, int unused)
  * that drbd_set_out_of_sync() can not be called. This function MAY ONLY be
  * called from worker context. It MUST NOT be used while a previous such
  * work is still pending!
+ *
+ * Its worker function encloses the call of io_fn() by get_ldev() and
+ * put_ldev().
  */
 void drbd_queue_bitmap_io(struct drbd_device *device,
                           int (*io_fn)(struct drbd_device *),
@@ -3685,25 +3651,7 @@ int drbd_md_test_flag(struct drbd_backing_dev *bdev, int flag)
 static void md_sync_timer_fn(unsigned long data)
 {
         struct drbd_device *device = (struct drbd_device *) data;
-
-        /* must not double-queue! */
-        if (list_empty(&device->md_sync_work.list))
-                drbd_queue_work_front(&first_peer_device(device)->connection->sender_work,
-                                      &device->md_sync_work);
-}
-
-static int w_md_sync(struct drbd_work *w, int unused)
-{
-        struct drbd_device *device =
-                container_of(w, struct drbd_device, md_sync_work);
-
-        drbd_warn(device, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
-#ifdef DEBUG
-        drbd_warn(device, "last md_mark_dirty: %s:%u\n",
-                device->last_md_mark_dirty.func, device->last_md_mark_dirty.line);
-#endif
-        drbd_md_sync(device);
-        return 0;
+        drbd_device_post_work(device, MD_SYNC);
 }
 
 const char *cmdname(enum drbd_packet cmd)
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 3f2e16738080..1cd47df44bda 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -23,6 +23,8 @@
 
  */
 
+#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
+
 #include <linux/module.h>
 #include <linux/drbd.h>
 #include <linux/in.h>
@@ -85,7 +87,7 @@ static void drbd_adm_send_reply(struct sk_buff *skb, struct genl_info *info)
 {
         genlmsg_end(skb, genlmsg_data(nlmsg_data(nlmsg_hdr(skb))));
         if (genlmsg_reply(skb, info))
-                printk(KERN_ERR "drbd: error sending genl reply\n");
+                pr_err("error sending genl reply\n");
 }
 
 /* Used on a fresh "drbd_adm_prepare"d reply_skb, this cannot fail: The only
@@ -558,8 +560,10 @@ void conn_try_outdate_peer_async(struct drbd_connection *connection)
 }
 
 enum drbd_state_rv
-drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
+drbd_set_role(struct drbd_device *const device, enum drbd_role new_role, int force)
 {
+        struct drbd_peer_device *const peer_device = first_peer_device(device);
+        struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
         const int max_tries = 4;
         enum drbd_state_rv rv = SS_UNKNOWN_ERROR;
         struct net_conf *nc;
@@ -607,7 +611,7 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
                     device->state.disk == D_CONSISTENT && mask.pdsk == 0) {
                         D_ASSERT(device, device->state.pdsk == D_UNKNOWN);
 
-                        if (conn_try_outdate_peer(first_peer_device(device)->connection)) {
+                        if (conn_try_outdate_peer(connection)) {
                                 val.disk = D_UP_TO_DATE;
                                 mask.disk = D_MASK;
                         }
@@ -617,7 +621,7 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
                 if (rv == SS_NOTHING_TO_DO)
                         goto out;
                 if (rv == SS_PRIMARY_NOP && mask.pdsk == 0) {
-                        if (!conn_try_outdate_peer(first_peer_device(device)->connection) && force) {
+                        if (!conn_try_outdate_peer(connection) && force) {
                                 drbd_warn(device, "Forced into split brain situation!\n");
                                 mask.pdsk = D_MASK;
                                 val.pdsk  = D_OUTDATED;
@@ -630,7 +634,7 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
                            retry at most once more in this case. */
                         int timeo;
                         rcu_read_lock();
-                        nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+                        nc = rcu_dereference(connection->net_conf);
                         timeo = nc ? (nc->ping_timeo + 1) * HZ / 10 : 1;
                         rcu_read_unlock();
                         schedule_timeout_interruptible(timeo);
@@ -659,19 +663,17 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
         /* FIXME also wait for all pending P_BARRIER_ACK? */
 
         if (new_role == R_SECONDARY) {
-                set_disk_ro(device->vdisk, true);
                 if (get_ldev(device)) {
                         device->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;
                         put_ldev(device);
                 }
         } else {
-                /* Called from drbd_adm_set_role only.
-                 * We are still holding the conf_update mutex. */
-                nc = first_peer_device(device)->connection->net_conf;
+                mutex_lock(&device->resource->conf_update);
+                nc = connection->net_conf;
                 if (nc)
                         nc->discard_my_data = 0; /* without copy; single bit op is atomic */
+                mutex_unlock(&device->resource->conf_update);
 
-                set_disk_ro(device->vdisk, false);
                 if (get_ldev(device)) {
                         if (((device->state.conn < C_CONNECTED ||
                                device->state.pdsk <= D_FAILED)
@@ -689,12 +691,12 @@ drbd_set_role(struct drbd_device *device, enum drbd_role new_role, int force)
         if (device->state.conn >= C_WF_REPORT_PARAMS) {
                 /* if this was forced, we should consider sync */
                 if (forced)
-                        drbd_send_uuids(first_peer_device(device));
-                drbd_send_current_state(first_peer_device(device));
+                        drbd_send_uuids(peer_device);
+                drbd_send_current_state(peer_device);
         }
 
         drbd_md_sync(device);
-
+        set_disk_ro(device->vdisk, new_role == R_SECONDARY);
         kobject_uevent(&disk_to_dev(device->vdisk)->kobj, KOBJ_CHANGE);
 out:
         mutex_unlock(device->state_mutex);
@@ -891,7 +893,7 @@ drbd_determine_dev_size(struct drbd_device *device, enum dds_flags flags, struct
          * still lock the act_log to not trigger ASSERTs there.
          */
         drbd_suspend_io(device);
-        buffer = drbd_md_get_buffer(device); /* Lock meta-data IO */
+        buffer = drbd_md_get_buffer(device, __func__); /* Lock meta-data IO */
         if (!buffer) {
                 drbd_resume_io(device);
                 return DS_ERROR;
@@ -971,6 +973,10 @@ drbd_determine_dev_size(struct drbd_device *device, enum dds_flags flags, struct
         if (la_size_changed || md_moved || rs) {
                 u32 prev_flags;
 
+                /* We do some synchronous IO below, which may take some time.
+                 * Clear the timer, to avoid scary "timer expired!" messages,
+                 * "Superblock" is written out at least twice below, anyways. */
+                del_timer(&device->md_sync_timer);
                 drbd_al_shrink(device); /* All extents inactive. */
 
                 prev_flags = md->flags;
@@ -1116,15 +1122,16 @@ static int drbd_check_al_size(struct drbd_device *device, struct disk_conf *dc)
         return 0;
 }
 
-static void drbd_setup_queue_param(struct drbd_device *device, unsigned int max_bio_size)
+static void drbd_setup_queue_param(struct drbd_device *device, struct drbd_backing_dev *bdev,
+                                   unsigned int max_bio_size)
 {
         struct request_queue * const q = device->rq_queue;
         unsigned int max_hw_sectors = max_bio_size >> 9;
         unsigned int max_segments = 0;
         struct request_queue *b = NULL;
 
-        if (get_ldev_if_state(device, D_ATTACHING)) {
-                b = device->ldev->backing_bdev->bd_disk->queue;
+        if (bdev) {
+                b = bdev->backing_bdev->bd_disk->queue;
 
                 max_hw_sectors = min(queue_max_hw_sectors(b), max_bio_size >> 9);
                 rcu_read_lock();
@@ -1169,11 +1176,10 @@ static void drbd_setup_queue_param(struct drbd_device *device, unsigned int max_
                                  b->backing_dev_info.ra_pages);
                         q->backing_dev_info.ra_pages = b->backing_dev_info.ra_pages;
                 }
-                put_ldev(device);
         }
 }
 
-void drbd_reconsider_max_bio_size(struct drbd_device *device)
+void drbd_reconsider_max_bio_size(struct drbd_device *device, struct drbd_backing_dev *bdev)
 {
         unsigned int now, new, local, peer;
 
@@ -1181,10 +1187,9 @@ void drbd_reconsider_max_bio_size(struct drbd_device *device)
         local = device->local_max_bio_size; /* Eventually last known value, from volatile memory */
         peer = device->peer_max_bio_size; /* Eventually last known value, from meta data */
 
-        if (get_ldev_if_state(device, D_ATTACHING)) {
-                local = queue_max_hw_sectors(device->ldev->backing_bdev->bd_disk->queue) << 9;
+        if (bdev) {
+                local = queue_max_hw_sectors(bdev->backing_bdev->bd_disk->queue) << 9;
                 device->local_max_bio_size = local;
-                put_ldev(device);
         }
         local = min(local, DRBD_MAX_BIO_SIZE);
 
@@ -1217,7 +1222,7 @@ void drbd_reconsider_max_bio_size(struct drbd_device *device)
         if (new != now)
                 drbd_info(device, "max BIO size = %u\n", new);
 
-        drbd_setup_queue_param(device, new);
+        drbd_setup_queue_param(device, bdev, new);
 }
 
 /* Starts the worker thread */
@@ -1299,6 +1304,13 @@ static unsigned int drbd_al_extents_max(struct drbd_backing_dev *bdev)
         return (al_size_4k - 1) * AL_CONTEXT_PER_TRANSACTION;
 }
 
+static bool write_ordering_changed(struct disk_conf *a, struct disk_conf *b)
+{
+        return  a->disk_barrier != b->disk_barrier ||
+                a->disk_flushes != b->disk_flushes ||
+                a->disk_drain != b->disk_drain;
+}
+
 int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
 {
         struct drbd_config_context adm_ctx;
@@ -1405,7 +1417,8 @@ int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
         else
                 set_bit(MD_NO_FUA, &device->flags);
 
-        drbd_bump_write_ordering(first_peer_device(device)->connection, WO_bdev_flush);
+        if (write_ordering_changed(old_disk_conf, new_disk_conf))
+                drbd_bump_write_ordering(device->resource, NULL, WO_bdev_flush);
 
         drbd_md_sync(device);
 
@@ -1440,6 +1453,8 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 {
         struct drbd_config_context adm_ctx;
         struct drbd_device *device;
+        struct drbd_peer_device *peer_device;
+        struct drbd_connection *connection;
         int err;
         enum drbd_ret_code retcode;
         enum determine_dev_size dd;
@@ -1462,7 +1477,9 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 
         device = adm_ctx.device;
         mutex_lock(&adm_ctx.resource->adm_mutex);
-        conn_reconfig_start(first_peer_device(device)->connection);
+        peer_device = first_peer_device(device);
+        connection = peer_device ? peer_device->connection : NULL;
+        conn_reconfig_start(connection);
 
         /* if you want to reconfigure, please tear down first */
         if (device->state.disk > D_DISKLESS) {
@@ -1473,7 +1490,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
          * drbd_ldev_destroy is done already, we may end up here very fast,
          * e.g. if someone calls attach from the on-io-error handler,
          * to realize a "hot spare" feature (not that I'd recommend that) */
-        wait_event(device->misc_wait, !atomic_read(&device->local_cnt));
+        wait_event(device->misc_wait, !test_bit(GOING_DISKLESS, &device->flags));
 
         /* make sure there is no leftover from previous force-detach attempts */
         clear_bit(FORCE_DETACH, &device->flags);
@@ -1529,7 +1546,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
                 goto fail;
 
         rcu_read_lock();
-        nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+        nc = rcu_dereference(connection->net_conf);
         if (nc) {
                 if (new_disk_conf->fencing == FP_STONITH && nc->wire_protocol == DRBD_PROT_A) {
                         rcu_read_unlock();
@@ -1649,7 +1666,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
          */
         wait_event(device->misc_wait, !atomic_read(&device->ap_pending_cnt) || drbd_suspended(device));
         /* and for any other previously queued work */
-        drbd_flush_workqueue(&first_peer_device(device)->connection->sender_work);
+        drbd_flush_workqueue(&connection->sender_work);
 
         rv = _drbd_request_state(device, NS(disk, D_ATTACHING), CS_VERBOSE);
         retcode = rv;  /* FIXME: Type mismatch. */
@@ -1710,7 +1727,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
         new_disk_conf = NULL;
         new_plan = NULL;
 
-        drbd_bump_write_ordering(first_peer_device(device)->connection, WO_bdev_flush);
+        drbd_bump_write_ordering(device->resource, device->ldev, WO_bdev_flush);
 
         if (drbd_md_test_flag(device->ldev, MDF_CRASHED_PRIMARY))
                 set_bit(CRASHED_PRIMARY, &device->flags);
@@ -1726,7 +1743,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
         device->read_cnt = 0;
         device->writ_cnt = 0;
 
-        drbd_reconsider_max_bio_size(device);
+        drbd_reconsider_max_bio_size(device, device->ldev);
 
         /* If I am currently not R_PRIMARY,
          * but meta data primary indicator is set,
@@ -1845,7 +1862,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
 
         kobject_uevent(&disk_to_dev(device->vdisk)->kobj, KOBJ_CHANGE);
         put_ldev(device);
-        conn_reconfig_done(first_peer_device(device)->connection);
+        conn_reconfig_done(connection);
         mutex_unlock(&adm_ctx.resource->adm_mutex);
         drbd_adm_finish(&adm_ctx, info, retcode);
         return 0;
@@ -1856,7 +1873,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
         drbd_force_state(device, NS(disk, D_DISKLESS));
         drbd_md_sync(device);
  fail:
-        conn_reconfig_done(first_peer_device(device)->connection);
+        conn_reconfig_done(connection);
         if (nbc) {
                 if (nbc->backing_bdev)
                         blkdev_put(nbc->backing_bdev,
@@ -1888,7 +1905,7 @@ static int adm_detach(struct drbd_device *device, int force)
         }
 
         drbd_suspend_io(device); /* so no-one is stuck in drbd_al_begin_io */
-        drbd_md_get_buffer(device); /* make sure there is no in-flight meta-data IO */
+        drbd_md_get_buffer(device, __func__); /* make sure there is no in-flight meta-data IO */
         retcode = drbd_request_state(device, NS(disk, D_FAILED));
         drbd_md_put_buffer(device);
         /* D_FAILED will transition to DISKLESS. */
@@ -2654,8 +2671,13 @@ int drbd_adm_invalidate(struct sk_buff *skb, struct genl_info *info)
         if (retcode != NO_ERROR)
                 goto out;
 
-        mutex_lock(&adm_ctx.resource->adm_mutex);
         device = adm_ctx.device;
+        if (!get_ldev(device)) {
+                retcode = ERR_NO_DISK;
+                goto out;
+        }
+
+        mutex_lock(&adm_ctx.resource->adm_mutex);
 
         /* If there is still bitmap IO pending, probably because of a previous
          * resync just being finished, wait for it before requesting a new resync.
@@ -2679,6 +2701,7 @@ int drbd_adm_invalidate(struct sk_buff *skb, struct genl_info *info)
                 retcode = drbd_request_state(device, NS(conn, C_STARTING_SYNC_T));
         drbd_resume_io(device);
         mutex_unlock(&adm_ctx.resource->adm_mutex);
+        put_ldev(device);
 out:
         drbd_adm_finish(&adm_ctx, info, retcode);
         return 0;
@@ -2704,7 +2727,7 @@ out:
         return 0;
 }
 
-static int drbd_bmio_set_susp_al(struct drbd_device *device)
+static int drbd_bmio_set_susp_al(struct drbd_device *device) __must_hold(local)
 {
         int rv;
 
@@ -2725,8 +2748,13 @@ int drbd_adm_invalidate_peer(struct sk_buff *skb, struct genl_info *info)
         if (retcode != NO_ERROR)
                 goto out;
 
-        mutex_lock(&adm_ctx.resource->adm_mutex);
         device = adm_ctx.device;
+        if (!get_ldev(device)) {
+                retcode = ERR_NO_DISK;
+                goto out;
+        }
+
+        mutex_lock(&adm_ctx.resource->adm_mutex);
 
         /* If there is still bitmap IO pending, probably because of a previous
          * resync just being finished, wait for it before requesting a new resync.
@@ -2753,6 +2781,7 @@ int drbd_adm_invalidate_peer(struct sk_buff *skb, struct genl_info *info)
                 retcode = drbd_request_state(device, NS(conn, C_STARTING_SYNC_S));
         drbd_resume_io(device);
         mutex_unlock(&adm_ctx.resource->adm_mutex);
+        put_ldev(device);
 out:
         drbd_adm_finish(&adm_ctx, info, retcode);
         return 0;
@@ -2892,7 +2921,7 @@ static struct drbd_connection *the_only_connection(struct drbd_resource *resourc
         return list_first_entry(&resource->connections, struct drbd_connection, connections);
 }
 
-int nla_put_status_info(struct sk_buff *skb, struct drbd_device *device,
+static int nla_put_status_info(struct sk_buff *skb, struct drbd_device *device,
                 const struct sib_info *sib)
 {
         struct drbd_resource *resource = device->resource;
@@ -3622,13 +3651,6 @@ void drbd_bcast_event(struct drbd_device *device, const struct sib_info *sib)
         unsigned seq;
         int err = -ENOMEM;
 
-        if (sib->sib_reason == SIB_SYNC_PROGRESS) {
-                if (time_after(jiffies, device->rs_last_bcast + HZ))
-                        device->rs_last_bcast = jiffies;
-                else
-                        return;
-        }
-
         seq = atomic_inc_return(&drbd_genl_seq);
         msg = genlmsg_new(NLMSG_GOODSIZE, GFP_NOIO);
         if (!msg)
diff --git a/drivers/block/drbd/drbd_proc.c b/drivers/block/drbd/drbd_proc.c
index 89736bdbbc70..06e6147c7601 100644
--- a/drivers/block/drbd/drbd_proc.c
+++ b/drivers/block/drbd/drbd_proc.c
@@ -60,20 +60,65 @@ static void seq_printf_with_thousands_grouping(struct seq_file *seq, long v)
                 seq_printf(seq, "%ld", v);
 }
 
+static void drbd_get_syncer_progress(struct drbd_device *device,
+                union drbd_dev_state state, unsigned long *rs_total,
+                unsigned long *bits_left, unsigned int *per_mil_done)
+{
+        /* this is to break it at compile time when we change that, in case we
+         * want to support more than (1<<32) bits on a 32bit arch. */
+        typecheck(unsigned long, device->rs_total);
+        *rs_total = device->rs_total;
+
+        /* note: both rs_total and rs_left are in bits, i.e. in
+         * units of BM_BLOCK_SIZE.
+         * for the percentage, we don't care. */
+
+        if (state.conn == C_VERIFY_S || state.conn == C_VERIFY_T)
+                *bits_left = device->ov_left;
+        else
+                *bits_left = drbd_bm_total_weight(device) - device->rs_failed;
+        /* >> 10 to prevent overflow,
+         * +1 to prevent division by zero */
+        if (*bits_left > *rs_total) {
+                /* D'oh. Maybe a logic bug somewhere.  More likely just a race
+                 * between state change and reset of rs_total.
+                 */
+                *bits_left = *rs_total;
+                *per_mil_done = *rs_total ? 0 : 1000;
+        } else {
+                /* Make sure the division happens in long context.
+                 * We allow up to one petabyte storage right now,
+                 * at a granularity of 4k per bit that is 2**38 bits.
+                 * After shift right and multiplication by 1000,
+                 * this should still fit easily into a 32bit long,
+                 * so we don't need a 64bit division on 32bit arch.
+                 * Note: currently we don't support such large bitmaps on 32bit
+                 * arch anyways, but no harm done to be prepared for it here.
+                 */
+                unsigned int shift = *rs_total > UINT_MAX ? 16 : 10;
+                unsigned long left = *bits_left >> shift;
+                unsigned long total = 1UL + (*rs_total >> shift);
+                unsigned long tmp = 1000UL - left * 1000UL/total;
+                *per_mil_done = tmp;
+        }
+}
+
+
 /*lge
  * progress bars shamelessly adapted from driver/md/md.c
  * output looks like
  *      [=====>..............] 33.5% (23456/123456)
  *      finish: 2:20:20 speed: 6,345 (6,456) K/sec
  */
-static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *seq)
+static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *seq,
+                union drbd_dev_state state)
 {
-        unsigned long db, dt, dbdt, rt, rs_left;
+        unsigned long db, dt, dbdt, rt, rs_total, rs_left;
         unsigned int res;
         int i, x, y;
         int stalled = 0;
 
-        drbd_get_syncer_progress(device, &rs_left, &res);
+        drbd_get_syncer_progress(device, state, &rs_total, &rs_left, &res);
 
         x = res/50;
         y = 20-x;
@@ -85,21 +130,21 @@ static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *se
                 seq_printf(seq, ".");
         seq_printf(seq, "] ");
 
-        if (device->state.conn == C_VERIFY_S || device->state.conn == C_VERIFY_T)
+        if (state.conn == C_VERIFY_S || state.conn == C_VERIFY_T)
                 seq_printf(seq, "verified:");
         else
                 seq_printf(seq, "sync'ed:");
         seq_printf(seq, "%3u.%u%% ", res / 10, res % 10);
 
         /* if more than a few GB, display in MB */
-        if (device->rs_total > (4UL << (30 - BM_BLOCK_SHIFT)))
+        if (rs_total > (4UL << (30 - BM_BLOCK_SHIFT)))
                 seq_printf(seq, "(%lu/%lu)M",
                             (unsigned long) Bit2KB(rs_left >> 10),
-                            (unsigned long) Bit2KB(device->rs_total >> 10));
+                            (unsigned long) Bit2KB(rs_total >> 10));
         else
                 seq_printf(seq, "(%lu/%lu)K\n\t",
                             (unsigned long) Bit2KB(rs_left),
-                            (unsigned long) Bit2KB(device->rs_total));
+                            (unsigned long) Bit2KB(rs_total));
 
         /* see drivers/md/md.c
          * We do not want to overflow, so the order of operands and
@@ -150,13 +195,13 @@ static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *se
         dt = (jiffies - device->rs_start - device->rs_paused) / HZ;
         if (dt == 0)
                 dt = 1;
-        db = device->rs_total - rs_left;
+        db = rs_total - rs_left;
         dbdt = Bit2KB(db/dt);
         seq_printf_with_thousands_grouping(seq, dbdt);
         seq_printf(seq, ")");
 
-        if (device->state.conn == C_SYNC_TARGET ||
-            device->state.conn == C_VERIFY_S) {
+        if (state.conn == C_SYNC_TARGET ||
+            state.conn == C_VERIFY_S) {
                 seq_printf(seq, " want: ");
                 seq_printf_with_thousands_grouping(seq, device->c_sync_rate);
         }
@@ -168,8 +213,8 @@ static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *se
                 unsigned long bm_bits = drbd_bm_bits(device);
                 unsigned long bit_pos;
                 unsigned long long stop_sector = 0;
-                if (device->state.conn == C_VERIFY_S ||
-                    device->state.conn == C_VERIFY_T) {
+                if (state.conn == C_VERIFY_S ||
+                    state.conn == C_VERIFY_T) {
                         bit_pos = bm_bits - device->ov_left;
                         if (verify_can_do_stop_sector(device))
                                 stop_sector = device->ov_stop_sector;
@@ -188,22 +233,13 @@ static void drbd_syncer_progress(struct drbd_device *device, struct seq_file *se
         }
 }
 
-static void resync_dump_detail(struct seq_file *seq, struct lc_element *e)
-{
-        struct bm_extent *bme = lc_entry(e, struct bm_extent, lce);
-
-        seq_printf(seq, "%5d %s %s\n", bme->rs_left,
-                   bme->flags & BME_NO_WRITES ? "NO_WRITES" : "---------",
-                   bme->flags & BME_LOCKED ? "LOCKED" : "------"
-                   );
-}
-
 static int drbd_seq_show(struct seq_file *seq, void *v)
 {
         int i, prev_i = -1;
         const char *sn;
         struct drbd_device *device;
         struct net_conf *nc;
+        union drbd_dev_state state;
         char wp;
 
         static char write_ordering_chars[] = {
@@ -241,11 +277,12 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
                         seq_printf(seq, "\n");
                 prev_i = i;
 
-                sn = drbd_conn_str(device->state.conn);
+                state = device->state;
+                sn = drbd_conn_str(state.conn);
 
-                if (device->state.conn == C_STANDALONE &&
-                    device->state.disk == D_DISKLESS &&
-                    device->state.role == R_SECONDARY) {
+                if (state.conn == C_STANDALONE &&
+                    state.disk == D_DISKLESS &&
+                    state.role == R_SECONDARY) {
                         seq_printf(seq, "%2d: cs:Unconfigured\n", i);
                 } else {
                         /* reset device->congestion_reason */
@@ -258,15 +295,15 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
                            "    ns:%u nr:%u dw:%u dr:%u al:%u bm:%u "
                            "lo:%d pe:%d ua:%d ap:%d ep:%d wo:%c",
                            i, sn,
-                           drbd_role_str(device->state.role),
-                           drbd_role_str(device->state.peer),
-                           drbd_disk_str(device->state.disk),
-                           drbd_disk_str(device->state.pdsk),
+                           drbd_role_str(state.role),
+                           drbd_role_str(state.peer),
+                           drbd_disk_str(state.disk),
+                           drbd_disk_str(state.pdsk),
                            wp,
                            drbd_suspended(device) ? 's' : 'r',
-                           device->state.aftr_isp ? 'a' : '-',
-                           device->state.peer_isp ? 'p' : '-',
-                           device->state.user_isp ? 'u' : '-',
+                           state.aftr_isp ? 'a' : '-',
+                           state.peer_isp ? 'p' : '-',
+                           state.user_isp ? 'u' : '-',
                            device->congestion_reason ?: '-',
                            test_bit(AL_SUSPENDED, &device->flags) ? 's' : '-',
                            device->send_cnt/2,
@@ -281,17 +318,17 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
                            atomic_read(&device->unacked_cnt),
                            atomic_read(&device->ap_bio_cnt),
                            first_peer_device(device)->connection->epochs,
-                           write_ordering_chars[first_peer_device(device)->connection->write_ordering]
+                           write_ordering_chars[device->resource->write_ordering]
                         );
                         seq_printf(seq, " oos:%llu\n",
                                    Bit2KB((unsigned long long)
                                            drbd_bm_total_weight(device)));
                 }
-                if (device->state.conn == C_SYNC_SOURCE ||
-                    device->state.conn == C_SYNC_TARGET ||
-                    device->state.conn == C_VERIFY_S ||
-                    device->state.conn == C_VERIFY_T)
-                        drbd_syncer_progress(device, seq);
+                if (state.conn == C_SYNC_SOURCE ||
+                    state.conn == C_SYNC_TARGET ||
+                    state.conn == C_VERIFY_S ||
+                    state.conn == C_VERIFY_T)
+                        drbd_syncer_progress(device, seq, state);
 
                 if (proc_details >= 1 && get_ldev_if_state(device, D_FAILED)) {
                         lc_seq_printf_stats(seq, device->resync);
@@ -299,12 +336,8 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
                         put_ldev(device);
                 }
 
-                if (proc_details >= 2) {
-                        if (device->resync) {
-                                lc_seq_dump_details(seq, device->resync, "rs_left",
-                                        resync_dump_detail);
-                        }
-                }
+                if (proc_details >= 2)
+                        seq_printf(seq, "\tblocked on activity log: %d\n", atomic_read(&device->ap_actlog_cnt));
         }
         rcu_read_unlock();
 
@@ -316,7 +349,7 @@ static int drbd_proc_open(struct inode *inode, struct file *file)
         int err;
 
         if (try_module_get(THIS_MODULE)) {
-                err = single_open(file, drbd_seq_show, PDE_DATA(inode));
+                err = single_open(file, drbd_seq_show, NULL);
                 if (err)
                         module_put(THIS_MODULE);
                 return err;
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 5b17ec88ea05..9342b8da73ab 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -362,17 +362,14 @@ drbd_alloc_peer_req(struct drbd_peer_device *peer_device, u64 id, sector_t secto
                         goto fail;
         }
 
+        memset(peer_req, 0, sizeof(*peer_req));
+        INIT_LIST_HEAD(&peer_req->w.list);
         drbd_clear_interval(&peer_req->i);
         peer_req->i.size = data_size;
         peer_req->i.sector = sector;
-        peer_req->i.local = false;
-        peer_req->i.waiting = false;
-
-        peer_req->epoch = NULL;
+        peer_req->submit_jif = jiffies;
         peer_req->peer_device = peer_device;
         peer_req->pages = page;
-        atomic_set(&peer_req->pending_bios, 0);
-        peer_req->flags = 0;
         /*
          * The block_id is opaque to the receiver.  It is not endianness
          * converted, and sent back to the sender unchanged.
@@ -389,11 +386,16 @@ drbd_alloc_peer_req(struct drbd_peer_device *peer_device, u64 id, sector_t secto
 void __drbd_free_peer_req(struct drbd_device *device, struct drbd_peer_request *peer_req,
                        int is_net)
 {
+        might_sleep();
         if (peer_req->flags & EE_HAS_DIGEST)
                 kfree(peer_req->digest);
         drbd_free_pages(device, peer_req->pages, is_net);
         D_ASSERT(device, atomic_read(&peer_req->pending_bios) == 0);
         D_ASSERT(device, drbd_interval_empty(&peer_req->i));
+        if (!expect(!(peer_req->flags & EE_CALL_AL_COMPLETE_IO))) {
+                peer_req->flags &= ~EE_CALL_AL_COMPLETE_IO;
+                drbd_al_complete_io(device, &peer_req->i);
+        }
         mempool_free(peer_req, drbd_ee_mempool);
 }
 
@@ -791,8 +793,18 @@ static int receive_first_packet(struct drbd_connection *connection, struct socke
 {
         unsigned int header_size = drbd_header_size(connection);
         struct packet_info pi;
+        struct net_conf *nc;
         int err;
 
+        rcu_read_lock();
+        nc = rcu_dereference(connection->net_conf);
+        if (!nc) {
+                rcu_read_unlock();
+                return -EIO;
+        }
+        sock->sk->sk_rcvtimeo = nc->ping_timeo * 4 * HZ / 10;
+        rcu_read_unlock();
+
         err = drbd_recv_short(sock, connection->data.rbuf, header_size, 0);
         if (err != header_size) {
                 if (err >= 0)
@@ -809,7 +821,7 @@ static int receive_first_packet(struct drbd_connection *connection, struct socke
  * drbd_socket_okay() - Free the socket if its connection is not okay
  * @sock:       pointer to the pointer to the socket.
  */
-static int drbd_socket_okay(struct socket **sock)
+static bool drbd_socket_okay(struct socket **sock)
 {
         int rr;
         char tb[4];
@@ -827,6 +839,30 @@ static int drbd_socket_okay(struct socket **sock)
                 return false;
         }
 }
+
+static bool connection_established(struct drbd_connection *connection,
+                                   struct socket **sock1,
+                                   struct socket **sock2)
+{
+        struct net_conf *nc;
+        int timeout;
+        bool ok;
+
+        if (!*sock1 || !*sock2)
+                return false;
+
+        rcu_read_lock();
+        nc = rcu_dereference(connection->net_conf);
+        timeout = (nc->sock_check_timeo ?: nc->ping_timeo) * HZ / 10;
+        rcu_read_unlock();
+        schedule_timeout_interruptible(timeout);
+
+        ok = drbd_socket_okay(sock1);
+        ok = drbd_socket_okay(sock2) && ok;
+
+        return ok;
+}
+
 /* Gets called if a connection is established, or if a new minor gets created
    in a connection */
 int drbd_connected(struct drbd_peer_device *peer_device)
@@ -868,8 +904,8 @@ static int conn_connect(struct drbd_connection *connection)
         struct drbd_socket sock, msock;
         struct drbd_peer_device *peer_device;
         struct net_conf *nc;
-        int vnr, timeout, h, ok;
-        bool discard_my_data;
+        int vnr, timeout, h;
+        bool discard_my_data, ok;
         enum drbd_state_rv rv;
         struct accept_wait_data ad = {
                 .connection = connection,
@@ -913,17 +949,8 @@ static int conn_connect(struct drbd_connection *connection)
                         }
                 }
 
-                if (sock.socket && msock.socket) {
-                        rcu_read_lock();
-                        nc = rcu_dereference(connection->net_conf);
-                        timeout = nc->ping_timeo * HZ / 10;
-                        rcu_read_unlock();
-                        schedule_timeout_interruptible(timeout);
-                        ok = drbd_socket_okay(&sock.socket);
-                        ok = drbd_socket_okay(&msock.socket) && ok;
-                        if (ok)
-                                break;
-                }
+                if (connection_established(connection, &sock.socket, &msock.socket))
+                        break;
 
 retry:
                 s = drbd_wait_for_connect(connection, &ad);
@@ -969,8 +996,7 @@ randomize:
                                 goto out_release_sockets;
                 }
 
-                ok = drbd_socket_okay(&sock.socket);
-                ok = drbd_socket_okay(&msock.socket) && ok;
+                ok = connection_established(connection, &sock.socket, &msock.socket);
         } while (!ok);
 
         if (ad.s_listen)
@@ -1151,7 +1177,7 @@ static void drbd_flush(struct drbd_connection *connection)
         struct drbd_peer_device *peer_device;
         int vnr;
 
-        if (connection->write_ordering >= WO_bdev_flush) {
+        if (connection->resource->write_ordering >= WO_bdev_flush) {
                 rcu_read_lock();
                 idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
                         struct drbd_device *device = peer_device->device;
@@ -1161,14 +1187,22 @@ static void drbd_flush(struct drbd_connection *connection)
                         kref_get(&device->kref);
                         rcu_read_unlock();
 
+                        /* Right now, we have only this one synchronous code path
+                         * for flushes between request epochs.
+                         * We may want to make those asynchronous,
+                         * or at least parallelize the flushes to the volume devices.
+                         */
+                        device->flush_jif = jiffies;
+                        set_bit(FLUSH_PENDING, &device->flags);
                         rv = blkdev_issue_flush(device->ldev->backing_bdev,
                                         GFP_NOIO, NULL);
+                        clear_bit(FLUSH_PENDING, &device->flags);
                         if (rv) {
                                 drbd_info(device, "local disk flush failed with status %d\n", rv);
                                 /* would rather check on EOPNOTSUPP, but that is not reliable.
                                  * don't try again for ANY return value != 0
                                  * if (rv == -EOPNOTSUPP) */
-                                drbd_bump_write_ordering(connection, WO_drain_io);
+                                drbd_bump_write_ordering(connection->resource, NULL, WO_drain_io);
                         }
                         put_ldev(device);
                         kref_put(&device->kref, drbd_destroy_device);
@@ -1257,15 +1291,30 @@ static enum finish_epoch drbd_may_finish_epoch(struct drbd_connection *connectio
         return rv;
 }
 
+static enum write_ordering_e
+max_allowed_wo(struct drbd_backing_dev *bdev, enum write_ordering_e wo)
+{
+        struct disk_conf *dc;
+
+        dc = rcu_dereference(bdev->disk_conf);
+
+        if (wo == WO_bdev_flush && !dc->disk_flushes)
+                wo = WO_drain_io;
+        if (wo == WO_drain_io && !dc->disk_drain)
+                wo = WO_none;
+
+        return wo;
+}
+
 /**
  * drbd_bump_write_ordering() - Fall back to an other write ordering method
  * @connection: DRBD connection.
  * @wo:         Write ordering method to try.
  */
-void drbd_bump_write_ordering(struct drbd_connection *connection, enum write_ordering_e wo)
+void drbd_bump_write_ordering(struct drbd_resource *resource, struct drbd_backing_dev *bdev,
+                              enum write_ordering_e wo)
 {
-        struct disk_conf *dc;
-        struct drbd_peer_device *peer_device;
+        struct drbd_device *device;
         enum write_ordering_e pwo;
         int vnr;
         static char *write_ordering_str[] = {
@@ -1274,26 +1323,27 @@ void drbd_bump_write_ordering(struct drbd_connection *connection, enum write_ord
                 [WO_bdev_flush] = "flush",
         };
 
-        pwo = connection->write_ordering;
-        wo = min(pwo, wo);
+        pwo = resource->write_ordering;
+        if (wo != WO_bdev_flush)
+                wo = min(pwo, wo);
         rcu_read_lock();
-        idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
-                struct drbd_device *device = peer_device->device;
+        idr_for_each_entry(&resource->devices, device, vnr) {
+                if (get_ldev(device)) {
+                        wo = max_allowed_wo(device->ldev, wo);
+                        if (device->ldev == bdev)
+                                bdev = NULL;
+                        put_ldev(device);
+                }
+        }
 
-                if (!get_ldev_if_state(device, D_ATTACHING))
-                        continue;
-                dc = rcu_dereference(device->ldev->disk_conf);
+        if (bdev)
+                wo = max_allowed_wo(bdev, wo);
 
-                if (wo == WO_bdev_flush && !dc->disk_flushes)
-                        wo = WO_drain_io;
-                if (wo == WO_drain_io && !dc->disk_drain)
-                        wo = WO_none;
-                put_ldev(device);
-        }
         rcu_read_unlock();
-        connection->write_ordering = wo;
-        if (pwo != connection->write_ordering || wo == WO_bdev_flush)
-                drbd_info(connection, "Method to ensure write ordering: %s\n", write_ordering_str[connection->write_ordering]);
+
+        resource->write_ordering = wo;
+        if (pwo != resource->write_ordering || wo == WO_bdev_flush)
+                drbd_info(resource, "Method to ensure write ordering: %s\n", write_ordering_str[resource->write_ordering]);
 }
 
 /**
@@ -1330,6 +1380,13 @@ int drbd_submit_peer_request(struct drbd_device *device,
                 /* wait for all pending IO completions, before we start
                  * zeroing things out. */
                 conn_wait_active_ee_empty(first_peer_device(device)->connection);
+                /* add it to the active list now,
+                 * so we can find it to present it in debugfs */
+                peer_req->submit_jif = jiffies;
+                peer_req->flags |= EE_SUBMITTED;
+                spin_lock_irq(&device->resource->req_lock);
+                list_add_tail(&peer_req->w.list, &device->active_ee);
+                spin_unlock_irq(&device->resource->req_lock);
                 if (blkdev_issue_zeroout(device->ldev->backing_bdev,
                         sector, ds >> 9, GFP_NOIO))
                         peer_req->flags |= EE_WAS_ERROR;
@@ -1398,6 +1455,9 @@ submit:
         D_ASSERT(device, page == NULL);
 
         atomic_set(&peer_req->pending_bios, n_bios);
+        /* for debugfs: update timestamp, mark as submitted */
+        peer_req->submit_jif = jiffies;
+        peer_req->flags |= EE_SUBMITTED;
         do {
                 bio = bios;
                 bios = bios->bi_next;
@@ -1471,7 +1531,7 @@ static int receive_Barrier(struct drbd_connection *connection, struct packet_inf
          * R_PRIMARY crashes now.
          * Therefore we must send the barrier_ack after the barrier request was
          * completed. */
-        switch (connection->write_ordering) {
+        switch (connection->resource->write_ordering) {
         case WO_none:
                 if (rv == FE_RECYCLED)
                         return 0;
@@ -1498,7 +1558,8 @@ static int receive_Barrier(struct drbd_connection *connection, struct packet_inf
 
                 return 0;
         default:
-                drbd_err(connection, "Strangeness in connection->write_ordering %d\n", connection->write_ordering);
+                drbd_err(connection, "Strangeness in connection->write_ordering %d\n",
+                         connection->resource->write_ordering);
                 return -EIO;
         }
 
@@ -1531,7 +1592,7 @@ read_in_block(struct drbd_peer_device *peer_device, u64 id, sector_t sector,
         struct drbd_peer_request *peer_req;
         struct page *page;
         int dgs, ds, err;
-        int data_size = pi->size;
+        unsigned int data_size = pi->size;
         void *dig_in = peer_device->connection->int_dig_in;
         void *dig_vv = peer_device->connection->int_dig_vv;
         unsigned long *data;
@@ -1578,6 +1639,7 @@ read_in_block(struct drbd_peer_device *peer_device, u64 id, sector_t sector,
         if (!peer_req)
                 return NULL;
 
+        peer_req->flags |= EE_WRITE;
         if (trim)
                 return peer_req;
 
@@ -1734,9 +1796,10 @@ static int recv_resync_read(struct drbd_peer_device *peer_device, sector_t secto
          * respective _drbd_clear_done_ee */
 
         peer_req->w.cb = e_end_resync_block;
+        peer_req->submit_jif = jiffies;
 
         spin_lock_irq(&device->resource->req_lock);
-        list_add(&peer_req->w.list, &device->sync_ee);
+        list_add_tail(&peer_req->w.list, &device->sync_ee);
         spin_unlock_irq(&device->resource->req_lock);
 
         atomic_add(pi->size >> 9, &device->rs_sect_ev);
@@ -1889,6 +1952,7 @@ static int e_end_block(struct drbd_work *w, int cancel)
                 }
                 dec_unacked(device);
         }
+
         /* we delete from the conflict detection hash _after_ we sent out the
          * P_WRITE_ACK / P_NEG_ACK, to get the sequence number right.  */
         if (peer_req->flags & EE_IN_INTERVAL_TREE) {
@@ -2115,6 +2179,8 @@ static int handle_write_conflicts(struct drbd_device *device,
         drbd_for_each_overlap(i, &device->write_requests, sector, size) {
                 if (i == &peer_req->i)
                         continue;
+                if (i->completed)
+                        continue;
 
                 if (!i->local) {
                         /*
@@ -2147,7 +2213,6 @@ static int handle_write_conflicts(struct drbd_device *device,
                                           (unsigned long long)sector, size,
                                           superseded ? "local" : "remote");
 
-                        inc_unacked(device);
                         peer_req->w.cb = superseded ? e_send_superseded :
                                                    e_send_retry_write;
                         list_add_tail(&peer_req->w.list, &device->done_ee);
@@ -2206,6 +2271,7 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
 {
         struct drbd_peer_device *peer_device;
         struct drbd_device *device;
+        struct net_conf *nc;
         sector_t sector;
         struct drbd_peer_request *peer_req;
         struct p_data *p = pi->data;
@@ -2245,6 +2311,8 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
         }
 
         peer_req->w.cb = e_end_block;
+        peer_req->submit_jif = jiffies;
+        peer_req->flags |= EE_APPLICATION;
 
         dp_flags = be32_to_cpu(p->dp_flags);
         rw |= wire_flags_to_bio(dp_flags);
@@ -2271,9 +2339,36 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
         spin_unlock(&connection->epoch_lock);
 
         rcu_read_lock();
-        tp = rcu_dereference(peer_device->connection->net_conf)->two_primaries;
+        nc = rcu_dereference(peer_device->connection->net_conf);
+        tp = nc->two_primaries;
+        if (peer_device->connection->agreed_pro_version < 100) {
+                switch (nc->wire_protocol) {
+                case DRBD_PROT_C:
+                        dp_flags |= DP_SEND_WRITE_ACK;
+                        break;
+                case DRBD_PROT_B:
+                        dp_flags |= DP_SEND_RECEIVE_ACK;
+                        break;
+                }
+        }
         rcu_read_unlock();
+
+        if (dp_flags & DP_SEND_WRITE_ACK) {
+                peer_req->flags |= EE_SEND_WRITE_ACK;
+                inc_unacked(device);
+                /* corresponding dec_unacked() in e_end_block()
+                 * respective _drbd_clear_done_ee */
+        }
+
+        if (dp_flags & DP_SEND_RECEIVE_ACK) {
+                /* I really don't like it that the receiver thread
+                 * sends on the msock, but anyways */
+                drbd_send_ack(first_peer_device(device), P_RECV_ACK, peer_req);
+        }
+
         if (tp) {
+                /* two primaries implies protocol C */
+                D_ASSERT(device, dp_flags & DP_SEND_WRITE_ACK);
                 peer_req->flags |= EE_IN_INTERVAL_TREE;
                 err = wait_for_and_update_peer_seq(peer_device, peer_seq);
                 if (err)
@@ -2297,44 +2392,18 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
          * active_ee to become empty in drbd_submit_peer_request();
          * better not add ourselves here. */
         if ((peer_req->flags & EE_IS_TRIM_USE_ZEROOUT) == 0)
-                list_add(&peer_req->w.list, &device->active_ee);
+                list_add_tail(&peer_req->w.list, &device->active_ee);
         spin_unlock_irq(&device->resource->req_lock);
 
         if (device->state.conn == C_SYNC_TARGET)
                 wait_event(device->ee_wait, !overlapping_resync_write(device, peer_req));
 
-        if (peer_device->connection->agreed_pro_version < 100) {
-                rcu_read_lock();
-                switch (rcu_dereference(peer_device->connection->net_conf)->wire_protocol) {
-                case DRBD_PROT_C:
-                        dp_flags |= DP_SEND_WRITE_ACK;
-                        break;
-                case DRBD_PROT_B:
-                        dp_flags |= DP_SEND_RECEIVE_ACK;
-                        break;
-                }
-                rcu_read_unlock();
-        }
-
-        if (dp_flags & DP_SEND_WRITE_ACK) {
-                peer_req->flags |= EE_SEND_WRITE_ACK;
-                inc_unacked(device);
-                /* corresponding dec_unacked() in e_end_block()
-                 * respective _drbd_clear_done_ee */
-        }
-
-        if (dp_flags & DP_SEND_RECEIVE_ACK) {
-                /* I really don't like it that the receiver thread
-                 * sends on the msock, but anyways */
-                drbd_send_ack(first_peer_device(device), P_RECV_ACK, peer_req);
-        }
-
         if (device->state.pdsk < D_INCONSISTENT) {
                 /* In case we have the only disk of the cluster, */
                 drbd_set_out_of_sync(device, peer_req->i.sector, peer_req->i.size);
-                peer_req->flags |= EE_CALL_AL_COMPLETE_IO;
                 peer_req->flags &= ~EE_MAY_SET_IN_SYNC;
-                drbd_al_begin_io(device, &peer_req->i, true);
+                drbd_al_begin_io(device, &peer_req->i);
+                peer_req->flags |= EE_CALL_AL_COMPLETE_IO;
         }
 
         err = drbd_submit_peer_request(device, peer_req, rw, DRBD_FAULT_DT_WR);
@@ -2347,8 +2416,10 @@ static int receive_Data(struct drbd_connection *connection, struct packet_info *
         list_del(&peer_req->w.list);
         drbd_remove_epoch_entry_interval(device, peer_req);
         spin_unlock_irq(&device->resource->req_lock);
-        if (peer_req->flags & EE_CALL_AL_COMPLETE_IO)
+        if (peer_req->flags & EE_CALL_AL_COMPLETE_IO) {
+                peer_req->flags &= ~EE_CALL_AL_COMPLETE_IO;
                 drbd_al_complete_io(device, &peer_req->i);
+        }
 
 out_interrupted:
         drbd_may_finish_epoch(connection, peer_req->epoch, EV_PUT + EV_CLEANUP);
@@ -2368,13 +2439,14 @@ out_interrupted:
  * The current sync rate used here uses only the most recent two step marks,
  * to have a short time average so we can react faster.
  */
-bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector)
+bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector,
+                bool throttle_if_app_is_waiting)
 {
         struct lc_element *tmp;
-        bool throttle = true;
+        bool throttle = drbd_rs_c_min_rate_throttle(device);
 
-        if (!drbd_rs_c_min_rate_throttle(device))
-                return false;
+        if (!throttle || throttle_if_app_is_waiting)
+                return throttle;
 
         spin_lock_irq(&device->al_lock);
         tmp = lc_find(device->resync, BM_SECT_TO_EXT(sector));
@@ -2382,7 +2454,8 @@ bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector)
                 struct bm_extent *bm_ext = lc_entry(tmp, struct bm_extent, lce);
                 if (test_bit(BME_PRIORITY, &bm_ext->flags))
                         throttle = false;
-                /* Do not slow down if app IO is already waiting for this extent */
+                /* Do not slow down if app IO is already waiting for this extent,
+                 * and our progress is necessary for application IO to complete. */
         }
         spin_unlock_irq(&device->al_lock);
 
@@ -2407,7 +2480,9 @@ bool drbd_rs_c_min_rate_throttle(struct drbd_device *device)
         curr_events = (int)part_stat_read(&disk->part0, sectors[0]) +
                       (int)part_stat_read(&disk->part0, sectors[1]) -
                         atomic_read(&device->rs_sect_ev);
-        if (!device->rs_last_events || curr_events - device->rs_last_events > 64) {
+
+        if (atomic_read(&device->ap_actlog_cnt)
+            || !device->rs_last_events || curr_events - device->rs_last_events > 64) {
                 unsigned long rs_left;
                 int i;
 
@@ -2508,6 +2583,7 @@ static int receive_DataRequest(struct drbd_connection *connection, struct packet
                 peer_req->w.cb = w_e_end_data_req;
                 fault_type = DRBD_FAULT_DT_RD;
                 /* application IO, don't drbd_rs_begin_io */
+                peer_req->flags |= EE_APPLICATION;
                 goto submit;
 
         case P_RS_DATA_REQUEST:
@@ -2538,6 +2614,8 @@ static int receive_DataRequest(struct drbd_connection *connection, struct packet
                         peer_req->w.cb = w_e_end_csum_rs_req;
                         /* used in the sector offset progress display */
                         device->bm_resync_fo = BM_SECT_TO_BIT(sector);
+                        /* remember to report stats in drbd_resync_finished */
+                        device->use_csums = true;
                 } else if (pi->cmd == P_OV_REPLY) {
                         /* track progress, we may need to throttle */
                         atomic_add(size >> 9, &device->rs_sect_in);
@@ -2595,8 +2673,20 @@ static int receive_DataRequest(struct drbd_connection *connection, struct packet
          * we would also throttle its application reads.
          * In that case, throttling is done on the SyncTarget only.
          */
-        if (device->state.peer != R_PRIMARY && drbd_rs_should_slow_down(device, sector))
+
+        /* Even though this may be a resync request, we do add to "read_ee";
+         * "sync_ee" is only used for resync WRITEs.
+         * Add to list early, so debugfs can find this request
+         * even if we have to sleep below. */
+        spin_lock_irq(&device->resource->req_lock);
+        list_add_tail(&peer_req->w.list, &device->read_ee);
+        spin_unlock_irq(&device->resource->req_lock);
+
+        update_receiver_timing_details(connection, drbd_rs_should_slow_down);
+        if (device->state.peer != R_PRIMARY
+        && drbd_rs_should_slow_down(device, sector, false))
                 schedule_timeout_uninterruptible(HZ/10);
+        update_receiver_timing_details(connection, drbd_rs_begin_io);
         if (drbd_rs_begin_io(device, sector))
                 goto out_free_e;
 
@@ -2604,22 +2694,20 @@ submit_for_resync:
         atomic_add(size >> 9, &device->rs_sect_ev);
 
 submit:
+        update_receiver_timing_details(connection, drbd_submit_peer_request);
         inc_unacked(device);
-        spin_lock_irq(&device->resource->req_lock);
-        list_add_tail(&peer_req->w.list, &device->read_ee);
-        spin_unlock_irq(&device->resource->req_lock);
-
         if (drbd_submit_peer_request(device, peer_req, READ, fault_type) == 0)
                 return 0;
 
         /* don't care for the reason here */
         drbd_err(device, "submit failed, triggering re-connect\n");
+
+out_free_e:
         spin_lock_irq(&device->resource->req_lock);
         list_del(&peer_req->w.list);
         spin_unlock_irq(&device->resource->req_lock);
         /* no drbd_rs_complete_io(), we are dropping the connection anyways */
 
-out_free_e:
         put_ldev(device);
         drbd_free_peer_req(device, peer_req);
         return -EIO;
@@ -2842,8 +2930,10 @@ static void drbd_uuid_dump(struct drbd_device *device, char *text, u64 *uuid,
 -1091   requires proto 91
 -1096   requires proto 96
  */
-static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_hold(local)
+static int drbd_uuid_compare(struct drbd_device *const device, int *rule_nr) __must_hold(local)
 {
+        struct drbd_peer_device *const peer_device = first_peer_device(device);
+        struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
         u64 self, peer;
         int i, j;
 
@@ -2869,7 +2959,7 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
 
                 if (device->p_uuid[UI_BITMAP] == (u64)0 && device->ldev->md.uuid[UI_BITMAP] != (u64)0) {
 
-                        if (first_peer_device(device)->connection->agreed_pro_version < 91)
+                        if (connection->agreed_pro_version < 91)
                                 return -1091;
 
                         if ((device->ldev->md.uuid[UI_BITMAP] & ~((u64)1)) == (device->p_uuid[UI_HISTORY_START] & ~((u64)1)) &&
@@ -2892,7 +2982,7 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
 
                 if (device->ldev->md.uuid[UI_BITMAP] == (u64)0 && device->p_uuid[UI_BITMAP] != (u64)0) {
 
-                        if (first_peer_device(device)->connection->agreed_pro_version < 91)
+                        if (connection->agreed_pro_version < 91)
                                 return -1091;
 
                         if ((device->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (device->p_uuid[UI_BITMAP] & ~((u64)1)) &&
@@ -2925,7 +3015,7 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
                 case 1: /*  self_pri && !peer_pri */ return 1;
                 case 2: /* !self_pri &&  peer_pri */ return -1;
                 case 3: /*  self_pri &&  peer_pri */
-                        dc = test_bit(RESOLVE_CONFLICTS, &first_peer_device(device)->connection->flags);
+                        dc = test_bit(RESOLVE_CONFLICTS, &connection->flags);
                         return dc ? -1 : 1;
                 }
         }
@@ -2938,14 +3028,14 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
         *rule_nr = 51;
         peer = device->p_uuid[UI_HISTORY_START] & ~((u64)1);
         if (self == peer) {
-                if (first_peer_device(device)->connection->agreed_pro_version < 96 ?
+                if (connection->agreed_pro_version < 96 ?
                     (device->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) ==
                     (device->p_uuid[UI_HISTORY_START + 1] & ~((u64)1)) :
                     peer + UUID_NEW_BM_OFFSET == (device->p_uuid[UI_BITMAP] & ~((u64)1))) {
                         /* The last P_SYNC_UUID did not get though. Undo the last start of
                            resync as sync source modifications of the peer's UUIDs. */
 
-                        if (first_peer_device(device)->connection->agreed_pro_version < 91)
+                        if (connection->agreed_pro_version < 91)
                                 return -1091;
 
                         device->p_uuid[UI_BITMAP] = device->p_uuid[UI_HISTORY_START];
@@ -2975,14 +3065,14 @@ static int drbd_uuid_compare(struct drbd_device *device, int *rule_nr) __must_ho
         *rule_nr = 71;
         self = device->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
         if (self == peer) {
-                if (first_peer_device(device)->connection->agreed_pro_version < 96 ?
+                if (connection->agreed_pro_version < 96 ?
                     (device->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) ==
                     (device->p_uuid[UI_HISTORY_START] & ~((u64)1)) :
                     self + UUID_NEW_BM_OFFSET == (device->ldev->md.uuid[UI_BITMAP] & ~((u64)1))) {
                         /* The last P_SYNC_UUID did not get though. Undo the last start of
                            resync as sync source modifications of our UUIDs. */
 
-                        if (first_peer_device(device)->connection->agreed_pro_version < 91)
+                        if (connection->agreed_pro_version < 91)
                                 return -1091;
 
                         __drbd_uuid_set(device, UI_BITMAP, device->ldev->md.uuid[UI_HISTORY_START]);
@@ -3352,8 +3442,7 @@ disconnect:
  * return: NULL (alg name was "")
  *         ERR_PTR(error) if something goes wrong
  *         or the crypto hash ptr, if it worked out ok. */
-static
-struct crypto_hash *drbd_crypto_alloc_digest_safe(const struct drbd_device *device,
+static struct crypto_hash *drbd_crypto_alloc_digest_safe(const struct drbd_device *device,
                 const char *alg, const char *name)
 {
         struct crypto_hash *tfm;
@@ -3639,7 +3728,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
         struct drbd_device *device;
         struct p_sizes *p = pi->data;
         enum determine_dev_size dd = DS_UNCHANGED;
-        sector_t p_size, p_usize, my_usize;
+        sector_t p_size, p_usize, p_csize, my_usize;
         int ldsc = 0; /* local disk size changed */
         enum dds_flags ddsf;
 
@@ -3650,6 +3739,7 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
 
         p_size = be64_to_cpu(p->d_size);
         p_usize = be64_to_cpu(p->u_size);
+        p_csize = be64_to_cpu(p->c_size);
 
         /* just store the peer's disk size for now.
          * we still need to figure out whether we accept that. */
@@ -3710,7 +3800,6 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
         }
 
         device->peer_max_bio_size = be32_to_cpu(p->max_bio_size);
-        drbd_reconsider_max_bio_size(device);
         /* Leave drbd_reconsider_max_bio_size() before drbd_determine_dev_size().
            In case we cleared the QUEUE_FLAG_DISCARD from our queue in
            drbd_reconsider_max_bio_size(), we can be sure that after
@@ -3718,14 +3807,28 @@ static int receive_sizes(struct drbd_connection *connection, struct packet_info
 
         ddsf = be16_to_cpu(p->dds_flags);
         if (get_ldev(device)) {
+                drbd_reconsider_max_bio_size(device, device->ldev);
                 dd = drbd_determine_dev_size(device, ddsf, NULL);
                 put_ldev(device);
                 if (dd == DS_ERROR)
                         return -EIO;
                 drbd_md_sync(device);
         } else {
-                /* I am diskless, need to accept the peer's size. */
-                drbd_set_my_capacity(device, p_size);
+                /*
+                 * I am diskless, need to accept the peer's *current* size.
+                 * I must NOT accept the peers backing disk size,
+                 * it may have been larger than mine all along...
+                 *
+                 * At this point, the peer knows more about my disk, or at
+                 * least about what we last agreed upon, than myself.
+                 * So if his c_size is less than his d_size, the most likely
+                 * reason is that *my* d_size was smaller last time we checked.
+                 *
+                 * However, if he sends a zero current size,
+                 * take his (user-capped or) backing disk size anyways.
+                 */
+                drbd_reconsider_max_bio_size(device, NULL);
+                drbd_set_my_capacity(device, p_csize ?: p_usize ?: p_size);
         }
 
         if (get_ldev(device)) {
@@ -4501,6 +4604,7 @@ static void drbdd(struct drbd_connection *connection)
                 struct data_cmd *cmd;
 
                 drbd_thread_current_set_cpu(&connection->receiver);
+                update_receiver_timing_details(connection, drbd_recv_header);
                 if (drbd_recv_header(connection, &pi))
                         goto err_out;
 
@@ -4519,12 +4623,14 @@ static void drbdd(struct drbd_connection *connection)
                 }
 
                 if (shs) {
+                        update_receiver_timing_details(connection, drbd_recv_all_warn);
                         err = drbd_recv_all_warn(connection, pi.data, shs);
                         if (err)
                                 goto err_out;
                         pi.size -= shs;
                 }
 
+                update_receiver_timing_details(connection, cmd->fn);
                 err = cmd->fn(connection, &pi);
                 if (err) {
                         drbd_err(connection, "error receiving %s, e: %d l: %d!\n",
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 09803d0d5207..c67717d572d1 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -52,7 +52,7 @@ static void _drbd_start_io_acct(struct drbd_device *device, struct drbd_request
 static void _drbd_end_io_acct(struct drbd_device *device, struct drbd_request *req)
 {
         int rw = bio_data_dir(req->master_bio);
-        unsigned long duration = jiffies - req->start_time;
+        unsigned long duration = jiffies - req->start_jif;
         int cpu;
         cpu = part_stat_lock();
         part_stat_add(cpu, &device->vdisk->part0, ticks[rw], duration);
@@ -66,7 +66,7 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device,
 {
         struct drbd_request *req;
 
-        req = mempool_alloc(drbd_request_mempool, GFP_NOIO);
+        req = mempool_alloc(drbd_request_mempool, GFP_NOIO | __GFP_ZERO);
         if (!req)
                 return NULL;
 
@@ -84,6 +84,8 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device,
 
         INIT_LIST_HEAD(&req->tl_requests);
         INIT_LIST_HEAD(&req->w.list);
+        INIT_LIST_HEAD(&req->req_pending_master_completion);
+        INIT_LIST_HEAD(&req->req_pending_local);
 
         /* one reference to be put by __drbd_make_request */
         atomic_set(&req->completion_ref, 1);
@@ -92,6 +94,19 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device,
         return req;
 }
 
+static void drbd_remove_request_interval(struct rb_root *root,
+                                         struct drbd_request *req)
+{
+        struct drbd_device *device = req->device;
+        struct drbd_interval *i = &req->i;
+
+        drbd_remove_interval(root, i);
+
+        /* Wake up any processes waiting for this request to complete.  */
+        if (i->waiting)
+                wake_up(&device->misc_wait);
+}
+
 void drbd_req_destroy(struct kref *kref)
 {
         struct drbd_request *req = container_of(kref, struct drbd_request, kref);
@@ -107,14 +122,30 @@ void drbd_req_destroy(struct kref *kref)
                 return;
         }
 
-        /* remove it from the transfer log.
-         * well, only if it had been there in the first
-         * place... if it had not (local only or conflicting
-         * and never sent), it should still be "empty" as
-         * initialized in drbd_req_new(), so we can list_del() it
-         * here unconditionally */
+        /* If called from mod_rq_state (expected normal case) or
+         * drbd_send_and_submit (the less likely normal path), this holds the
+         * req_lock, and req->tl_requests will typicaly be on ->transfer_log,
+         * though it may be still empty (never added to the transfer log).
+         *
+         * If called from do_retry(), we do NOT hold the req_lock, but we are
+         * still allowed to unconditionally list_del(&req->tl_requests),
+         * because it will be on a local on-stack list only. */
         list_del_init(&req->tl_requests);
 
+        /* finally remove the request from the conflict detection
+         * respective block_id verification interval tree. */
+        if (!drbd_interval_empty(&req->i)) {
+                struct rb_root *root;
+
+                if (s & RQ_WRITE)
+                        root = &device->write_requests;
+                else
+                        root = &device->read_requests;
+                drbd_remove_request_interval(root, req);
+        } else if (s & (RQ_NET_MASK & ~RQ_NET_DONE) && req->i.size != 0)
+                drbd_err(device, "drbd_req_destroy: Logic BUG: interval empty, but: rq_state=0x%x, sect=%llu, size=%u\n",
+                        s, (unsigned long long)req->i.sector, req->i.size);
+
         /* if it was a write, we may have to set the corresponding
          * bit(s) out-of-sync first. If it had a local part, we need to
          * release the reference to the activity log. */
@@ -188,19 +219,6 @@ void complete_master_bio(struct drbd_device *device,
 }
 
 
-static void drbd_remove_request_interval(struct rb_root *root,
-                                         struct drbd_request *req)
-{
-        struct drbd_device *device = req->device;
-        struct drbd_interval *i = &req->i;
-
-        drbd_remove_interval(root, i);
-
-        /* Wake up any processes waiting for this request to complete.  */
-        if (i->waiting)
-                wake_up(&device->misc_wait);
-}
-
 /* Helper for __req_mod().
  * Set m->bio to the master bio, if it is fit to be completed,
  * or leave it alone (it is initialized to NULL in __req_mod),
@@ -254,18 +272,6 @@ void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
         ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
         error = PTR_ERR(req->private_bio);
 
-        /* remove the request from the conflict detection
-         * respective block_id verification hash */
-        if (!drbd_interval_empty(&req->i)) {
-                struct rb_root *root;
-
-                if (rw == WRITE)
-                        root = &device->write_requests;
-                else
-                        root = &device->read_requests;
-                drbd_remove_request_interval(root, req);
-        }
-
         /* Before we can signal completion to the upper layers,
          * we may need to close the current transfer log epoch.
          * We are within the request lock, so we can simply compare
@@ -301,9 +307,24 @@ void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
                 m->error = ok ? 0 : (error ?: -EIO);
                 m->bio = req->master_bio;
                 req->master_bio = NULL;
+                /* We leave it in the tree, to be able to verify later
+                 * write-acks in protocol != C during resync.
+                 * But we mark it as "complete", so it won't be counted as
+                 * conflict in a multi-primary setup. */
+                req->i.completed = true;
         }
+
+        if (req->i.waiting)
+                wake_up(&device->misc_wait);
+
+        /* Either we are about to complete to upper layers,
+         * or we will restart this request.
+         * In either case, the request object will be destroyed soon,
+         * so better remove it from all lists. */
+        list_del_init(&req->req_pending_master_completion);
 }
 
+/* still holds resource->req_lock */
 static int drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_error *m, int put)
 {
         struct drbd_device *device = req->device;
@@ -324,12 +345,91 @@ static int drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_
         return 1;
 }
 
+static void set_if_null_req_next(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+        if (!connection)
+                return;
+        if (connection->req_next == NULL)
+                connection->req_next = req;
+}
+
+static void advance_conn_req_next(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+        if (!connection)
+                return;
+        if (connection->req_next != req)
+                return;
+        list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
+                const unsigned s = req->rq_state;
+                if (s & RQ_NET_QUEUED)
+                        break;
+        }
+        if (&req->tl_requests == &connection->transfer_log)
+                req = NULL;
+        connection->req_next = req;
+}
+
+static void set_if_null_req_ack_pending(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+        if (!connection)
+                return;
+        if (connection->req_ack_pending == NULL)
+                connection->req_ack_pending = req;
+}
+
+static void advance_conn_req_ack_pending(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+        if (!connection)
+                return;
+        if (connection->req_ack_pending != req)
+                return;
+        list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
+                const unsigned s = req->rq_state;
+                if ((s & RQ_NET_SENT) && (s & RQ_NET_PENDING))
+                        break;
+        }
+        if (&req->tl_requests == &connection->transfer_log)
+                req = NULL;
+        connection->req_ack_pending = req;
+}
+
+static void set_if_null_req_not_net_done(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+        if (!connection)
+                return;
+        if (connection->req_not_net_done == NULL)
+                connection->req_not_net_done = req;
+}
+
+static void advance_conn_req_not_net_done(struct drbd_peer_device *peer_device, struct drbd_request *req)
+{
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
+        if (!connection)
+                return;
+        if (connection->req_not_net_done != req)
+                return;
+        list_for_each_entry_continue(req, &connection->transfer_log, tl_requests) {
+                const unsigned s = req->rq_state;
+                if ((s & RQ_NET_SENT) && !(s & RQ_NET_DONE))
+                        break;
+        }
+        if (&req->tl_requests == &connection->transfer_log)
+                req = NULL;
+        connection->req_not_net_done = req;
+}
+
 /* I'd like this to be the only place that manipulates
  * req->completion_ref and req->kref. */
 static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
                 int clear, int set)
 {
         struct drbd_device *device = req->device;
+        struct drbd_peer_device *peer_device = first_peer_device(device);
         unsigned s = req->rq_state;
         int c_put = 0;
         int k_put = 0;
@@ -356,14 +456,23 @@ static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
                 atomic_inc(&req->completion_ref);
         }
 
-        if (!(s & RQ_NET_QUEUED) && (set & RQ_NET_QUEUED))
+        if (!(s & RQ_NET_QUEUED) && (set & RQ_NET_QUEUED)) {
                 atomic_inc(&req->completion_ref);
+                set_if_null_req_next(peer_device, req);
+        }
 
         if (!(s & RQ_EXP_BARR_ACK) && (set & RQ_EXP_BARR_ACK))
                 kref_get(&req->kref); /* wait for the DONE */
 
-        if (!(s & RQ_NET_SENT) && (set & RQ_NET_SENT))
-                atomic_add(req->i.size >> 9, &device->ap_in_flight);
+        if (!(s & RQ_NET_SENT) && (set & RQ_NET_SENT)) {
+                /* potentially already completed in the asender thread */
+                if (!(s & RQ_NET_DONE)) {
+                        atomic_add(req->i.size >> 9, &device->ap_in_flight);
+                        set_if_null_req_not_net_done(peer_device, req);
+                }
+                if (s & RQ_NET_PENDING)
+                        set_if_null_req_ack_pending(peer_device, req);
+        }
 
         if (!(s & RQ_COMPLETION_SUSP) && (set & RQ_COMPLETION_SUSP))
                 atomic_inc(&req->completion_ref);
@@ -386,20 +495,34 @@ static void mod_rq_state(struct drbd_request *req, struct bio_and_error *m,
                         ++k_put;
                 else
                         ++c_put;
+                list_del_init(&req->req_pending_local);
         }
 
         if ((s & RQ_NET_PENDING) && (clear & RQ_NET_PENDING)) {
                 dec_ap_pending(device);
                 ++c_put;
+                req->acked_jif = jiffies;
+                advance_conn_req_ack_pending(peer_device, req);
         }
 
-        if ((s & RQ_NET_QUEUED) && (clear & RQ_NET_QUEUED))
+        if ((s & RQ_NET_QUEUED) && (clear & RQ_NET_QUEUED)) {
                 ++c_put;
+                advance_conn_req_next(peer_device, req);
+        }
 
-        if ((s & RQ_EXP_BARR_ACK) && !(s & RQ_NET_DONE) && (set & RQ_NET_DONE)) {
-                if (req->rq_state & RQ_NET_SENT)
+        if (!(s & RQ_NET_DONE) && (set & RQ_NET_DONE)) {
+                if (s & RQ_NET_SENT)
                         atomic_sub(req->i.size >> 9, &device->ap_in_flight);
-                ++k_put;
+                if (s & RQ_EXP_BARR_ACK)
+                        ++k_put;
+                req->net_done_jif = jiffies;
+
+                /* in ahead/behind mode, or just in case,
+                 * before we finally destroy this request,
+                 * the caching pointers must not reference it anymore */
+                advance_conn_req_next(peer_device, req);
+                advance_conn_req_ack_pending(peer_device, req);
+                advance_conn_req_not_net_done(peer_device, req);
         }
 
         /* potentially complete and destroy */
@@ -439,6 +562,19 @@ static void drbd_report_io_error(struct drbd_device *device, struct drbd_request
                         bdevname(device->ldev->backing_bdev, b));
 }
 
+/* Helper for HANDED_OVER_TO_NETWORK.
+ * Is this a protocol A write (neither WRITE_ACK nor RECEIVE_ACK expected)?
+ * Is it also still "PENDING"?
+ * --> If so, clear PENDING and set NET_OK below.
+ * If it is a protocol A write, but not RQ_PENDING anymore, neg-ack was faster
+ * (and we must not set RQ_NET_OK) */
+static inline bool is_pending_write_protocol_A(struct drbd_request *req)
+{
+        return (req->rq_state &
+                   (RQ_WRITE|RQ_NET_PENDING|RQ_EXP_WRITE_ACK|RQ_EXP_RECEIVE_ACK))
+                == (RQ_WRITE|RQ_NET_PENDING);
+}
+
 /* obviously this could be coded as many single functions
  * instead of one huge switch,
  * or by putting the code directly in the respective locations
@@ -454,7 +590,9 @@ static void drbd_report_io_error(struct drbd_device *device, struct drbd_request
 int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 struct bio_and_error *m)
 {
-        struct drbd_device *device = req->device;
+        struct drbd_device *const device = req->device;
+        struct drbd_peer_device *const peer_device = first_peer_device(device);
+        struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
         struct net_conf *nc;
         int p, rv = 0;
 
@@ -477,7 +615,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                  * and from w_read_retry_remote */
                 D_ASSERT(device, !(req->rq_state & RQ_NET_MASK));
                 rcu_read_lock();
-                nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+                nc = rcu_dereference(connection->net_conf);
                 p = nc->wire_protocol;
                 rcu_read_unlock();
                 req->rq_state |=
@@ -549,7 +687,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 D_ASSERT(device, (req->rq_state & RQ_LOCAL_MASK) == 0);
                 mod_rq_state(req, m, 0, RQ_NET_QUEUED);
                 req->w.cb = w_send_read_req;
-                drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+                drbd_queue_work(&connection->sender_work,
                                 &req->w);
                 break;
 
@@ -585,23 +723,23 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
                 mod_rq_state(req, m, 0, RQ_NET_QUEUED|RQ_EXP_BARR_ACK);
                 req->w.cb =  w_send_dblock;
-                drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+                drbd_queue_work(&connection->sender_work,
                                 &req->w);
 
                 /* close the epoch, in case it outgrew the limit */
                 rcu_read_lock();
-                nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+                nc = rcu_dereference(connection->net_conf);
                 p = nc->max_epoch_size;
                 rcu_read_unlock();
-                if (first_peer_device(device)->connection->current_tle_writes >= p)
-                        start_new_tl_epoch(first_peer_device(device)->connection);
+                if (connection->current_tle_writes >= p)
+                        start_new_tl_epoch(connection);
 
                 break;
 
         case QUEUE_FOR_SEND_OOS:
                 mod_rq_state(req, m, 0, RQ_NET_QUEUED);
                 req->w.cb =  w_send_out_of_sync;
-                drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+                drbd_queue_work(&connection->sender_work,
                                 &req->w);
                 break;
 
@@ -615,18 +753,16 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
         case HANDED_OVER_TO_NETWORK:
                 /* assert something? */
-                if (bio_data_dir(req->master_bio) == WRITE &&
-                    !(req->rq_state & (RQ_EXP_RECEIVE_ACK | RQ_EXP_WRITE_ACK))) {
+                if (is_pending_write_protocol_A(req))
                         /* this is what is dangerous about protocol A:
                          * pretend it was successfully written on the peer. */
-                        if (req->rq_state & RQ_NET_PENDING)
-                                mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
-                        /* else: neg-ack was faster... */
-                        /* it is still not yet RQ_NET_DONE until the
-                         * corresponding epoch barrier got acked as well,
-                         * so we know what to dirty on connection loss */
-                }
-                mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_SENT);
+                        mod_rq_state(req, m, RQ_NET_QUEUED|RQ_NET_PENDING,
+                                                RQ_NET_SENT|RQ_NET_OK);
+                else
+                        mod_rq_state(req, m, RQ_NET_QUEUED, RQ_NET_SENT);
+                /* It is still not yet RQ_NET_DONE until the
+                 * corresponding epoch barrier got acked as well,
+                 * so we know what to dirty on connection loss. */
                 break;
 
         case OOS_HANDED_TO_NETWORK:
@@ -658,12 +794,13 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
         case WRITE_ACKED_BY_PEER_AND_SIS:
                 req->rq_state |= RQ_NET_SIS;
         case WRITE_ACKED_BY_PEER:
-                D_ASSERT(device, req->rq_state & RQ_EXP_WRITE_ACK);
-                /* protocol C; successfully written on peer.
+                /* Normal operation protocol C: successfully written on peer.
+                 * During resync, even in protocol != C,
+                 * we requested an explicit write ack anyways.
+                 * Which means we cannot even assert anything here.
                  * Nothing more to do here.
                  * We want to keep the tl in place for all protocols, to cater
                  * for volatile write-back caches on lower level devices. */
-
                 goto ack_common;
         case RECV_ACKED_BY_PEER:
                 D_ASSERT(device, req->rq_state & RQ_EXP_RECEIVE_ACK);
@@ -671,7 +808,6 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                  * see also notes above in HANDED_OVER_TO_NETWORK about
                  * protocol != C */
         ack_common:
-                D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
                 break;
 
@@ -714,7 +850,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
                 get_ldev(device); /* always succeeds in this call path */
                 req->w.cb = w_restart_disk_io;
-                drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+                drbd_queue_work(&connection->sender_work,
                                 &req->w);
                 break;
 
@@ -736,7 +872,8 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
                         mod_rq_state(req, m, RQ_COMPLETION_SUSP, RQ_NET_QUEUED|RQ_NET_PENDING);
                         if (req->w.cb) {
-                                drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+                                /* w.cb expected to be w_send_dblock, or w_send_read_req */
+                                drbd_queue_work(&connection->sender_work,
                                                 &req->w);
                                 rv = req->rq_state & RQ_WRITE ? MR_WRITE : MR_READ;
                         } /* else: FIXME can this happen? */
@@ -769,7 +906,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 break;
 
         case QUEUE_AS_DRBD_BARRIER:
-                start_new_tl_epoch(first_peer_device(device)->connection);
+                start_new_tl_epoch(connection);
                 mod_rq_state(req, m, 0, RQ_NET_OK|RQ_NET_DONE);
                 break;
         };
@@ -886,6 +1023,9 @@ static void maybe_pull_ahead(struct drbd_device *device)
             connection->agreed_pro_version < 96)
                 return;
 
+        if (on_congestion == OC_PULL_AHEAD && device->state.conn == C_AHEAD)
+                return; /* nothing to do ... */
+
         /* If I don't even have good local storage, we can not reasonably try
          * to pull ahead of the peer. We also need the local reference to make
          * sure device->act_log is there.
@@ -1021,6 +1161,7 @@ drbd_submit_req_private_bio(struct drbd_request *req)
          * stable storage, and this is a WRITE, we may not even submit
          * this bio. */
         if (get_ldev(device)) {
+                req->pre_submit_jif = jiffies;
                 if (drbd_insert_fault(device,
                                       rw == WRITE ? DRBD_FAULT_DT_WR
                                     : rw == READ  ? DRBD_FAULT_DT_RD
@@ -1035,10 +1176,14 @@ drbd_submit_req_private_bio(struct drbd_request *req)
 
 static void drbd_queue_write(struct drbd_device *device, struct drbd_request *req)
 {
-        spin_lock(&device->submit.lock);
+        spin_lock_irq(&device->resource->req_lock);
         list_add_tail(&req->tl_requests, &device->submit.writes);
-        spin_unlock(&device->submit.lock);
+        list_add_tail(&req->req_pending_master_completion,
+                        &device->pending_master_completion[1 /* WRITE */]);
+        spin_unlock_irq(&device->resource->req_lock);
         queue_work(device->submit.wq, &device->submit.worker);
+        /* do_submit() may sleep internally on al_wait, too */
+        wake_up(&device->al_wait);
 }
 
 /* returns the new drbd_request pointer, if the caller is expected to
@@ -1047,7 +1192,7 @@ static void drbd_queue_write(struct drbd_device *device, struct drbd_request *re
  * Returns ERR_PTR(-ENOMEM) if we cannot allocate a drbd_request.
  */
 static struct drbd_request *
-drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long start_time)
+drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long start_jif)
 {
         const int rw = bio_data_dir(bio);
         struct drbd_request *req;
@@ -1062,7 +1207,7 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long
                 bio_endio(bio, -ENOMEM);
                 return ERR_PTR(-ENOMEM);
         }
-        req->start_time = start_time;
+        req->start_jif = start_jif;
 
         if (!get_ldev(device)) {
                 bio_put(req->private_bio);
@@ -1075,10 +1220,12 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long
         if (rw == WRITE && req->private_bio && req->i.size
         && !test_bit(AL_SUSPENDED, &device->flags)) {
                 if (!drbd_al_begin_io_fastpath(device, &req->i)) {
+                        atomic_inc(&device->ap_actlog_cnt);
                         drbd_queue_write(device, req);
                         return NULL;
                 }
                 req->rq_state |= RQ_IN_ACT_LOG;
+                req->in_actlog_jif = jiffies;
         }
 
         return req;
@@ -1086,11 +1233,13 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long
 
 static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request *req)
 {
+        struct drbd_resource *resource = device->resource;
         const int rw = bio_rw(req->master_bio);
         struct bio_and_error m = { NULL, };
         bool no_remote = false;
+        bool submit_private_bio = false;
 
-        spin_lock_irq(&device->resource->req_lock);
+        spin_lock_irq(&resource->req_lock);
         if (rw == WRITE) {
                 /* This may temporarily give up the req_lock,
                  * but will re-aquire it before it returns here.
@@ -1148,13 +1297,18 @@ static void drbd_send_and_submit(struct drbd_device *device, struct drbd_request
                         no_remote = true;
         }
 
+        /* If it took the fast path in drbd_request_prepare, add it here.
+         * The slow path has added it already. */
+        if (list_empty(&req->req_pending_master_completion))
+                list_add_tail(&req->req_pending_master_completion,
+                        &device->pending_master_completion[rw == WRITE]);
         if (req->private_bio) {
                 /* needs to be marked within the same spinlock */
+                list_add_tail(&req->req_pending_local,
+                        &device->pending_completion[rw == WRITE]);
                 _req_mod(req, TO_BE_SUBMITTED);
                 /* but we need to give up the spinlock to submit */
-                spin_unlock_irq(&device->resource->req_lock);
-                drbd_submit_req_private_bio(req);
-                spin_lock_irq(&device->resource->req_lock);
+                submit_private_bio = true;
         } else if (no_remote) {
 nodata:
                 if (__ratelimit(&drbd_ratelimit_state))
@@ -1167,15 +1321,23 @@ nodata:
 out:
         if (drbd_req_put_completion_ref(req, &m, 1))
                 kref_put(&req->kref, drbd_req_destroy);
-        spin_unlock_irq(&device->resource->req_lock);
-
+        spin_unlock_irq(&resource->req_lock);
+
+        /* Even though above is a kref_put(), this is safe.
+         * As long as we still need to submit our private bio,
+         * we hold a completion ref, and the request cannot disappear.
+         * If however this request did not even have a private bio to submit
+         * (e.g. remote read), req may already be invalid now.
+         * That's why we cannot check on req->private_bio. */
+        if (submit_private_bio)
+                drbd_submit_req_private_bio(req);
         if (m.bio)
                 complete_master_bio(device, &m);
 }
 
-void __drbd_make_request(struct drbd_device *device, struct bio *bio, unsigned long start_time)
+void __drbd_make_request(struct drbd_device *device, struct bio *bio, unsigned long start_jif)
 {
-        struct drbd_request *req = drbd_request_prepare(device, bio, start_time);
+        struct drbd_request *req = drbd_request_prepare(device, bio, start_jif);
         if (IS_ERR_OR_NULL(req))
                 return;
         drbd_send_and_submit(device, req);
@@ -1194,6 +1356,8 @@ static void submit_fast_path(struct drbd_device *device, struct list_head *incom
                                 continue;
 
                         req->rq_state |= RQ_IN_ACT_LOG;
+                        req->in_actlog_jif = jiffies;
+                        atomic_dec(&device->ap_actlog_cnt);
                 }
 
                 list_del_init(&req->tl_requests);
@@ -1203,7 +1367,8 @@ static void submit_fast_path(struct drbd_device *device, struct list_head *incom
 
 static bool prepare_al_transaction_nonblock(struct drbd_device *device,
                                             struct list_head *incoming,
-                                            struct list_head *pending)
+                                            struct list_head *pending,
+                                            struct list_head *later)
 {
         struct drbd_request *req, *tmp;
         int wake = 0;
@@ -1212,45 +1377,105 @@ static bool prepare_al_transaction_nonblock(struct drbd_device *device,
         spin_lock_irq(&device->al_lock);
         list_for_each_entry_safe(req, tmp, incoming, tl_requests) {
                 err = drbd_al_begin_io_nonblock(device, &req->i);
+                if (err == -ENOBUFS)
+                        break;
                 if (err == -EBUSY)
                         wake = 1;
                 if (err)
-                        continue;
-                req->rq_state |= RQ_IN_ACT_LOG;
-                list_move_tail(&req->tl_requests, pending);
+                        list_move_tail(&req->tl_requests, later);
+                else
+                        list_move_tail(&req->tl_requests, pending);
         }
         spin_unlock_irq(&device->al_lock);
         if (wake)
                 wake_up(&device->al_wait);
-
         return !list_empty(pending);
 }
 
+void send_and_submit_pending(struct drbd_device *device, struct list_head *pending)
+{
+        struct drbd_request *req, *tmp;
+
+        list_for_each_entry_safe(req, tmp, pending, tl_requests) {
+                req->rq_state |= RQ_IN_ACT_LOG;
+                req->in_actlog_jif = jiffies;
+                atomic_dec(&device->ap_actlog_cnt);
+                list_del_init(&req->tl_requests);
+                drbd_send_and_submit(device, req);
+        }
+}
+
 void do_submit(struct work_struct *ws)
 {
         struct drbd_device *device = container_of(ws, struct drbd_device, submit.worker);
-        LIST_HEAD(incoming);
-        LIST_HEAD(pending);
-        struct drbd_request *req, *tmp;
+        LIST_HEAD(incoming);    /* from drbd_make_request() */
+        LIST_HEAD(pending);     /* to be submitted after next AL-transaction commit */
+        LIST_HEAD(busy);        /* blocked by resync requests */
+
+        /* grab new incoming requests */
+        spin_lock_irq(&device->resource->req_lock);
+        list_splice_tail_init(&device->submit.writes, &incoming);
+        spin_unlock_irq(&device->resource->req_lock);
 
         for (;;) {
-                spin_lock(&device->submit.lock);
-                list_splice_tail_init(&device->submit.writes, &incoming);
-                spin_unlock(&device->submit.lock);
+                DEFINE_WAIT(wait);
 
+                /* move used-to-be-busy back to front of incoming */
+                list_splice_init(&busy, &incoming);
                 submit_fast_path(device, &incoming);
                 if (list_empty(&incoming))
                         break;
 
-skip_fast_path:
-                wait_event(device->al_wait, prepare_al_transaction_nonblock(device, &incoming, &pending));
-                /* Maybe more was queued, while we prepared the transaction?
-                 * Try to stuff them into this transaction as well.
-                 * Be strictly non-blocking here, no wait_event, we already
-                 * have something to commit.
-                 * Stop if we don't make any more progres.
-                 */
                 for (;;) {
+                        prepare_to_wait(&device->al_wait, &wait, TASK_UNINTERRUPTIBLE);
+
+                        list_splice_init(&busy, &incoming);
+                        prepare_al_transaction_nonblock(device, &incoming, &pending, &busy);
+                        if (!list_empty(&pending))
+                                break;
+
+                        schedule();
+
+                        /* If all currently "hot" activity log extents are kept busy by
+                         * incoming requests, we still must not totally starve new
+                         * requests to "cold" extents.
+                         * Something left on &incoming means there had not been
+                         * enough update slots available, and the activity log
+                         * has been marked as "starving".
+                         *
+                         * Try again now, without looking for new requests,
+                         * effectively blocking all new requests until we made
+                         * at least _some_ progress with what we currently have.
+                         */
+                        if (!list_empty(&incoming))
+                                continue;
+
+                        /* Nothing moved to pending, but nothing left
+                         * on incoming: all moved to busy!
+                         * Grab new and iterate. */
+                        spin_lock_irq(&device->resource->req_lock);
+                        list_splice_tail_init(&device->submit.writes, &incoming);
+                        spin_unlock_irq(&device->resource->req_lock);
+                }
+                finish_wait(&device->al_wait, &wait);
+
+                /* If the transaction was full, before all incoming requests
+                 * had been processed, skip ahead to commit, and iterate
+                 * without splicing in more incoming requests from upper layers.
+                 *
+                 * Else, if all incoming have been processed,
+                 * they have become either "pending" (to be submitted after
+                 * next transaction commit) or "busy" (blocked by resync).
+                 *
+                 * Maybe more was queued, while we prepared the transaction?
+                 * Try to stuff those into this transaction as well.
+                 * Be strictly non-blocking here,
+                 * we already have something to commit.
+                 *
+                 * Commit if we don't make any more progres.
+                 */
+
+                while (list_empty(&incoming)) {
                         LIST_HEAD(more_pending);
                         LIST_HEAD(more_incoming);
                         bool made_progress;
@@ -1260,55 +1485,32 @@ skip_fast_path:
                         if (list_empty(&device->submit.writes))
                                 break;
 
-                        spin_lock(&device->submit.lock);
+                        spin_lock_irq(&device->resource->req_lock);
                         list_splice_tail_init(&device->submit.writes, &more_incoming);
-                        spin_unlock(&device->submit.lock);
+                        spin_unlock_irq(&device->resource->req_lock);
 
                         if (list_empty(&more_incoming))
                                 break;
 
-                        made_progress = prepare_al_transaction_nonblock(device, &more_incoming, &more_pending);
+                        made_progress = prepare_al_transaction_nonblock(device, &more_incoming, &more_pending, &busy);
 
                         list_splice_tail_init(&more_pending, &pending);
                         list_splice_tail_init(&more_incoming, &incoming);
-
                         if (!made_progress)
                                 break;
                 }
-                drbd_al_begin_io_commit(device, false);
-
-                list_for_each_entry_safe(req, tmp, &pending, tl_requests) {
-                        list_del_init(&req->tl_requests);
-                        drbd_send_and_submit(device, req);
-                }
 
-                /* If all currently hot activity log extents are kept busy by
-                 * incoming requests, we still must not totally starve new
-                 * requests to cold extents. In that case, prepare one request
-                 * in blocking mode. */
-                list_for_each_entry_safe(req, tmp, &incoming, tl_requests) {
-                        list_del_init(&req->tl_requests);
-                        req->rq_state |= RQ_IN_ACT_LOG;
-                        if (!drbd_al_begin_io_prepare(device, &req->i)) {
-                                /* Corresponding extent was hot after all? */
-                                drbd_send_and_submit(device, req);
-                        } else {
-                                /* Found a request to a cold extent.
-                                 * Put on "pending" list,
-                                 * and try to cumulate with more. */
-                                list_add(&req->tl_requests, &pending);
-                                goto skip_fast_path;
-                        }
-                }
+                drbd_al_begin_io_commit(device);
+                send_and_submit_pending(device, &pending);
         }
 }
 
 void drbd_make_request(struct request_queue *q, struct bio *bio)
 {
         struct drbd_device *device = (struct drbd_device *) q->queuedata;
-        unsigned long start_time;
+        unsigned long start_jif;
 
-        start_time = jiffies;
+        start_jif = jiffies;
 
         /*
          * what we "blindly" assume:
@@ -1316,7 +1518,7 @@ void drbd_make_request(struct request_queue *q, struct bio *bio)
         D_ASSERT(device, IS_ALIGNED(bio->bi_iter.bi_size, 512));
 
         inc_ap_bio(device);
-        __drbd_make_request(device, bio, start_time);
+        __drbd_make_request(device, bio, start_jif);
 }
 
 /* This is called by bio_add_page().
@@ -1353,36 +1555,13 @@ int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct
         return limit;
 }
 
-static void find_oldest_requests(
-                struct drbd_connection *connection,
-                struct drbd_device *device,
-                struct drbd_request **oldest_req_waiting_for_peer,
-                struct drbd_request **oldest_req_waiting_for_disk)
-{
-        struct drbd_request *r;
-        *oldest_req_waiting_for_peer = NULL;
-        *oldest_req_waiting_for_disk = NULL;
-        list_for_each_entry(r, &connection->transfer_log, tl_requests) {
-                const unsigned s = r->rq_state;
-                if (!*oldest_req_waiting_for_peer
-                && ((s & RQ_NET_MASK) && !(s & RQ_NET_DONE)))
-                        *oldest_req_waiting_for_peer = r;
-
-                if (!*oldest_req_waiting_for_disk
-                && (s & RQ_LOCAL_PENDING) && r->device == device)
-                        *oldest_req_waiting_for_disk = r;
-
-                if (*oldest_req_waiting_for_peer && *oldest_req_waiting_for_disk)
-                        break;
-        }
-}
-
 void request_timer_fn(unsigned long data)
 {
         struct drbd_device *device = (struct drbd_device *) data;
         struct drbd_connection *connection = first_peer_device(device)->connection;
-        struct drbd_request *req_disk, *req_peer; /* oldest request */
+        struct drbd_request *req_read, *req_write, *req_peer; /* oldest request */
         struct net_conf *nc;
+        unsigned long oldest_submit_jif;
         unsigned long ent = 0, dt = 0, et, nt; /* effective timeout = ko_count * timeout */
         unsigned long now;
 
@@ -1403,14 +1582,31 @@ void request_timer_fn(unsigned long data)
                 return; /* Recurring timer stopped */
 
         now = jiffies;
+        nt = now + et;
 
         spin_lock_irq(&device->resource->req_lock);
-        find_oldest_requests(connection, device, &req_peer, &req_disk);
-        if (req_peer == NULL && req_disk == NULL) {
-                spin_unlock_irq(&device->resource->req_lock);
-                mod_timer(&device->request_timer, now + et);
-                return;
-        }
+        req_read = list_first_entry_or_null(&device->pending_completion[0], struct drbd_request, req_pending_local);
+        req_write = list_first_entry_or_null(&device->pending_completion[1], struct drbd_request, req_pending_local);
+        req_peer = connection->req_not_net_done;
+        /* maybe the oldest request waiting for the peer is in fact still
+         * blocking in tcp sendmsg */
+        if (!req_peer && connection->req_next && connection->req_next->pre_send_jif)
+                req_peer = connection->req_next;
+
+        /* evaluate the oldest peer request only in one timer! */
+        if (req_peer && req_peer->device != device)
+                req_peer = NULL;
+
+        /* do we have something to evaluate? */
+        if (req_peer == NULL && req_write == NULL && req_read == NULL)
+                goto out;
+
+        oldest_submit_jif =
+                (req_write && req_read)
+                ? ( time_before(req_write->pre_submit_jif, req_read->pre_submit_jif)
+                  ? req_write->pre_submit_jif : req_read->pre_submit_jif )
+                : req_write ? req_write->pre_submit_jif
+                : req_read ? req_read->pre_submit_jif : now;
 
         /* The request is considered timed out, if
          * - we have some effective timeout from the configuration,
@@ -1429,13 +1625,13 @@ void request_timer_fn(unsigned long data)
          * to expire twice (worst case) to become effective. Good enough.
          */
         if (ent && req_peer &&
-                 time_after(now, req_peer->start_time + ent) &&
+                 time_after(now, req_peer->pre_send_jif + ent) &&
                 !time_in_range(now, connection->last_reconnect_jif, connection->last_reconnect_jif + ent)) {
                 drbd_warn(device, "Remote failed to finish a request within ko-count * timeout\n");
                 _drbd_set_state(_NS(device, conn, C_TIMEOUT), CS_VERBOSE | CS_HARD, NULL);
         }
-        if (dt && req_disk &&
-                 time_after(now, req_disk->start_time + dt) &&
+        if (dt && oldest_submit_jif != now &&
+                 time_after(now, oldest_submit_jif + dt) &&
                 !time_in_range(now, device->last_reattach_jif, device->last_reattach_jif + dt)) {
                 drbd_warn(device, "Local backing device failed to meet the disk-timeout\n");
                 __drbd_chk_io_error(device, DRBD_FORCE_DETACH);
@@ -1443,11 +1639,12 @@ void request_timer_fn(unsigned long data)
 
         /* Reschedule timer for the nearest not already expired timeout.
          * Fallback to now + min(effective network timeout, disk timeout). */
-        ent = (ent && req_peer && time_before(now, req_peer->start_time + ent))
-                ? req_peer->start_time + ent : now + et;
-        dt = (dt && req_disk && time_before(now, req_disk->start_time + dt))
-                ? req_disk->start_time + dt : now + et;
+        ent = (ent && req_peer && time_before(now, req_peer->pre_send_jif + ent))
+                ? req_peer->pre_send_jif + ent : now + et;
+        dt = (dt && oldest_submit_jif != now && time_before(now, oldest_submit_jif + dt))
+                ? oldest_submit_jif + dt : now + et;
         nt = time_before(ent, dt) ? ent : dt;
+out:
         spin_unlock_irq(&connection->resource->req_lock);
         mod_timer(&device->request_timer, nt);
 }
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index 8566cd5866b4..9f6a04080e9f 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -288,6 +288,7 @@ extern void complete_master_bio(struct drbd_device *device,
 extern void request_timer_fn(unsigned long data);
 extern void tl_restart(struct drbd_connection *connection, enum drbd_req_event what);
 extern void _tl_restart(struct drbd_connection *connection, enum drbd_req_event what);
+extern void tl_abort_disk_io(struct drbd_device *device);
 
 /* this is in drbd_main.c */
 extern void drbd_restart_request(struct drbd_request *req);
diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index a5d8aae00e04..c35c0f001bb7 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c
@@ -410,7 +410,7 @@ _drbd_request_state(struct drbd_device *device, union drbd_state mask,
         return rv;
 }
 
-static void print_st(struct drbd_device *device, char *name, union drbd_state ns)
+static void print_st(struct drbd_device *device, const char *name, union drbd_state ns)
 {
         drbd_err(device, " %s = { cs:%s ro:%s/%s ds:%s/%s %c%c%c%c%c%c }\n",
             name,
@@ -952,11 +952,12 @@ enum drbd_state_rv
 __drbd_set_state(struct drbd_device *device, union drbd_state ns,
                  enum chg_state_flags flags, struct completion *done)
 {
+        struct drbd_peer_device *peer_device = first_peer_device(device);
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
         union drbd_state os;
         enum drbd_state_rv rv = SS_SUCCESS;
         enum sanitize_state_warnings ssw;
         struct after_state_chg_work *ascw;
-        bool did_remote, should_do_remote;
 
         os = drbd_read_state(device);
 
@@ -978,9 +979,9 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
                            this happen...*/
 
                         if (is_valid_state(device, os) == rv)
-                                rv = is_valid_soft_transition(os, ns, first_peer_device(device)->connection);
+                                rv = is_valid_soft_transition(os, ns, connection);
                 } else
-                        rv = is_valid_soft_transition(os, ns, first_peer_device(device)->connection);
+                        rv = is_valid_soft_transition(os, ns, connection);
         }
 
         if (rv < SS_SUCCESS) {
@@ -997,7 +998,7 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
            sanitize_state(). Only display it here if we where not called from
            _conn_request_state() */
         if (!(flags & CS_DC_SUSP))
-                conn_pr_state_change(first_peer_device(device)->connection, os, ns,
+                conn_pr_state_change(connection, os, ns,
                                      (flags & ~CS_DC_MASK) | CS_DC_SUSP);
 
         /* if we are going -> D_FAILED or D_DISKLESS, grab one extra reference
@@ -1008,28 +1009,35 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
             (os.disk != D_DISKLESS && ns.disk == D_DISKLESS))
                 atomic_inc(&device->local_cnt);
 
-        did_remote = drbd_should_do_remote(device->state);
+        if (!is_sync_state(os.conn) && is_sync_state(ns.conn))
+                clear_bit(RS_DONE, &device->flags);
+
+        /* changes to local_cnt and device flags should be visible before
+         * changes to state, which again should be visible before anything else
+         * depending on that change happens. */
+        smp_wmb();
         device->state.i = ns.i;
-        should_do_remote = drbd_should_do_remote(device->state);
         device->resource->susp = ns.susp;
         device->resource->susp_nod = ns.susp_nod;
         device->resource->susp_fen = ns.susp_fen;
+        smp_wmb();
 
         /* put replicated vs not-replicated requests in seperate epochs */
-        if (did_remote != should_do_remote)
-                start_new_tl_epoch(first_peer_device(device)->connection);
+        if (drbd_should_do_remote((union drbd_dev_state)os.i) !=
+            drbd_should_do_remote((union drbd_dev_state)ns.i))
+                start_new_tl_epoch(connection);
 
         if (os.disk == D_ATTACHING && ns.disk >= D_NEGOTIATING)
                 drbd_print_uuids(device, "attached to UUIDs");
 
         /* Wake up role changes, that were delayed because of connection establishing */
         if (os.conn == C_WF_REPORT_PARAMS && ns.conn != C_WF_REPORT_PARAMS &&
-            no_peer_wf_report_params(first_peer_device(device)->connection))
-                clear_bit(STATE_SENT, &first_peer_device(device)->connection->flags);
+            no_peer_wf_report_params(connection))
+                clear_bit(STATE_SENT, &connection->flags);
 
         wake_up(&device->misc_wait);
         wake_up(&device->state_wait);
-        wake_up(&first_peer_device(device)->connection->ping_wait);
+        wake_up(&connection->ping_wait);
 
         /* Aborted verify run, or we reached the stop sector.
          * Log the last position, unless end-of-device. */
@@ -1118,21 +1126,21 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
 
         /* Receiver should clean up itself */
         if (os.conn != C_DISCONNECTING && ns.conn == C_DISCONNECTING)
-                drbd_thread_stop_nowait(&first_peer_device(device)->connection->receiver);
+                drbd_thread_stop_nowait(&connection->receiver);
 
         /* Now the receiver finished cleaning up itself, it should die */
         if (os.conn != C_STANDALONE && ns.conn == C_STANDALONE)
-                drbd_thread_stop_nowait(&first_peer_device(device)->connection->receiver);
+                drbd_thread_stop_nowait(&connection->receiver);
 
         /* Upon network failure, we need to restart the receiver. */
         if (os.conn > C_WF_CONNECTION &&
             ns.conn <= C_TEAR_DOWN && ns.conn >= C_TIMEOUT)
-                drbd_thread_restart_nowait(&first_peer_device(device)->connection->receiver);
+                drbd_thread_restart_nowait(&connection->receiver);
 
         /* Resume AL writing if we get a connection */
         if (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED) {
                 drbd_resume_al(device);
-                first_peer_device(device)->connection->connect_cnt++;
+                connection->connect_cnt++;
         }
 
         /* remember last attach time so request_timer_fn() won't
@@ -1150,7 +1158,7 @@ __drbd_set_state(struct drbd_device *device, union drbd_state ns,
                 ascw->w.cb = w_after_state_ch;
                 ascw->device = device;
                 ascw->done = done;
-                drbd_queue_work(&first_peer_device(device)->connection->sender_work,
+                drbd_queue_work(&connection->sender_work,
                                 &ascw->w);
         } else {
                 drbd_err(device, "Could not kmalloc an ascw\n");
@@ -1222,13 +1230,16 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
                            union drbd_state ns, enum chg_state_flags flags)
 {
         struct drbd_resource *resource = device->resource;
+        struct drbd_peer_device *peer_device = first_peer_device(device);
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
         struct sib_info sib;
 
         sib.sib_reason = SIB_STATE_CHANGE;
         sib.os = os;
         sib.ns = ns;
 
-        if (os.conn != C_CONNECTED && ns.conn == C_CONNECTED) {
+        if ((os.disk != D_UP_TO_DATE || os.pdsk != D_UP_TO_DATE)
+        &&  (ns.disk == D_UP_TO_DATE && ns.pdsk == D_UP_TO_DATE)) {
                 clear_bit(CRASHED_PRIMARY, &device->flags);
                 if (device->p_uuid)
                         device->p_uuid[UI_FLAGS] &= ~((u64)2);
@@ -1245,7 +1256,6 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
            state change. This function might sleep */
 
         if (ns.susp_nod) {
-                struct drbd_connection *connection = first_peer_device(device)->connection;
                 enum drbd_req_event what = NOTHING;
 
                 spin_lock_irq(&device->resource->req_lock);
@@ -1267,8 +1277,6 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
         }
 
         if (ns.susp_fen) {
-                struct drbd_connection *connection = first_peer_device(device)->connection;
-
                 spin_lock_irq(&device->resource->req_lock);
                 if (resource->susp_fen && conn_lowest_conn(connection) >= C_CONNECTED) {
                         /* case2: The connection was established again: */
@@ -1294,8 +1302,8 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
          * which is unexpected. */
         if ((os.conn != C_SYNC_SOURCE && os.conn != C_PAUSED_SYNC_S) &&
             (ns.conn == C_SYNC_SOURCE || ns.conn == C_PAUSED_SYNC_S) &&
-            first_peer_device(device)->connection->agreed_pro_version >= 96 && get_ldev(device)) {
-                drbd_gen_and_send_sync_uuid(first_peer_device(device));
+            connection->agreed_pro_version >= 96 && get_ldev(device)) {
+                drbd_gen_and_send_sync_uuid(peer_device);
                 put_ldev(device);
         }
 
@@ -1309,8 +1317,8 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
                 atomic_set(&device->rs_pending_cnt, 0);
                 drbd_rs_cancel_all(device);
 
-                drbd_send_uuids(first_peer_device(device));
-                drbd_send_state(first_peer_device(device), ns);
+                drbd_send_uuids(peer_device);
+                drbd_send_state(peer_device, ns);
         }
         /* No point in queuing send_bitmap if we don't have a connection
          * anymore, so check also the _current_ state, not only the new state
@@ -1335,7 +1343,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
                                         set_bit(NEW_CUR_UUID, &device->flags);
                                 } else {
                                         drbd_uuid_new_current(device);
-                                        drbd_send_uuids(first_peer_device(device));
+                                        drbd_send_uuids(peer_device);
                                 }
                         }
                         put_ldev(device);
@@ -1346,7 +1354,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
                 if (os.peer == R_SECONDARY && ns.peer == R_PRIMARY &&
                     device->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
                         drbd_uuid_new_current(device);
-                        drbd_send_uuids(first_peer_device(device));
+                        drbd_send_uuids(peer_device);
                 }
                 /* D_DISKLESS Peer becomes secondary */
                 if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
@@ -1373,16 +1381,16 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
         /* Last part of the attaching process ... */
         if (ns.conn >= C_CONNECTED &&
             os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
-                drbd_send_sizes(first_peer_device(device), 0, 0);  /* to start sync... */
-                drbd_send_uuids(first_peer_device(device));
-                drbd_send_state(first_peer_device(device), ns);
+                drbd_send_sizes(peer_device, 0, 0);  /* to start sync... */
+                drbd_send_uuids(peer_device);
+                drbd_send_state(peer_device, ns);
         }
 
         /* We want to pause/continue resync, tell peer. */
         if (ns.conn >= C_CONNECTED &&
              ((os.aftr_isp != ns.aftr_isp) ||
               (os.user_isp != ns.user_isp)))
-                drbd_send_state(first_peer_device(device), ns);
+                drbd_send_state(peer_device, ns);
 
         /* In case one of the isp bits got set, suspend other devices. */
         if ((!os.aftr_isp && !os.peer_isp && !os.user_isp) &&
@@ -1392,10 +1400,10 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
         /* Make sure the peer gets informed about eventual state
            changes (ISP bits) while we were in WFReportParams. */
         if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
-                drbd_send_state(first_peer_device(device), ns);
+                drbd_send_state(peer_device, ns);
 
         if (os.conn != C_AHEAD && ns.conn == C_AHEAD)
-                drbd_send_state(first_peer_device(device), ns);
+                drbd_send_state(peer_device, ns);
 
         /* We are in the progress to start a full sync... */
         if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
@@ -1449,7 +1457,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
                                         drbd_disk_str(device->state.disk));
 
                         if (ns.conn >= C_CONNECTED)
-                                drbd_send_state(first_peer_device(device), ns);
+                                drbd_send_state(peer_device, ns);
 
                         drbd_rs_cancel_all(device);
 
@@ -1473,7 +1481,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
                                  drbd_disk_str(device->state.disk));
 
                 if (ns.conn >= C_CONNECTED)
-                        drbd_send_state(first_peer_device(device), ns);
+                        drbd_send_state(peer_device, ns);
                 /* corresponding get_ldev in __drbd_set_state
                  * this may finally trigger drbd_ldev_destroy. */
                 put_ldev(device);
@@ -1481,7 +1489,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 
         /* Notify peer that I had a local IO error, and did not detached.. */
         if (os.disk == D_UP_TO_DATE && ns.disk == D_INCONSISTENT && ns.conn >= C_CONNECTED)
-                drbd_send_state(first_peer_device(device), ns);
+                drbd_send_state(peer_device, ns);
 
         /* Disks got bigger while they were detached */
         if (ns.disk > D_NEGOTIATING && ns.pdsk > D_NEGOTIATING &&
@@ -1499,14 +1507,14 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
         /* sync target done with resync.  Explicitly notify peer, even though
          * it should (at least for non-empty resyncs) already know itself. */
         if (os.disk < D_UP_TO_DATE && os.conn >= C_SYNC_SOURCE && ns.conn == C_CONNECTED)
-                drbd_send_state(first_peer_device(device), ns);
+                drbd_send_state(peer_device, ns);
 
         /* Verify finished, or reached stop sector.  Peer did not know about
          * the stop sector, and we may even have changed the stop sector during
          * verify to interrupt/stop early.  Send the new state. */
         if (os.conn == C_VERIFY_S && ns.conn == C_CONNECTED
         && verify_can_do_stop_sector(device))
-                drbd_send_state(first_peer_device(device), ns);
+                drbd_send_state(peer_device, ns);
 
         /* This triggers bitmap writeout of potentially still unwritten pages
          * if the resync finished cleanly, or aborted because of peer disk
@@ -1563,7 +1571,7 @@ static int w_after_conn_state_ch(struct drbd_work *w, int unused)
                 old_conf = connection->net_conf;
                 connection->my_addr_len = 0;
                 connection->peer_addr_len = 0;
-                rcu_assign_pointer(connection->net_conf, NULL);
+                RCU_INIT_POINTER(connection->net_conf, NULL);
                 conn_free_crypto(connection);
                 mutex_unlock(&connection->resource->conf_update);
 
@@ -1599,7 +1607,7 @@ static int w_after_conn_state_ch(struct drbd_work *w, int unused)
         return 0;
 }
 
-void conn_old_common_state(struct drbd_connection *connection, union drbd_state *pcs, enum chg_state_flags *pf)
+static void conn_old_common_state(struct drbd_connection *connection, union drbd_state *pcs, enum chg_state_flags *pf)
 {
         enum chg_state_flags flags = ~0;
         struct drbd_peer_device *peer_device;
@@ -1688,7 +1696,7 @@ conn_is_valid_transition(struct drbd_connection *connection, union drbd_state ma
         return rv;
 }
 
-void
+static void
 conn_set_state(struct drbd_connection *connection, union drbd_state mask, union drbd_state val,
                union drbd_state *pns_min, union drbd_state *pns_max, enum chg_state_flags flags)
 {
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index d8f57b6305cd..50776b362828 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -67,13 +67,10 @@ rwlock_t global_state_lock;
  */
 void drbd_md_io_complete(struct bio *bio, int error)
 {
-        struct drbd_md_io *md_io;
         struct drbd_device *device;
 
-        md_io = (struct drbd_md_io *)bio->bi_private;
-        device = container_of(md_io, struct drbd_device, md_io);
-
-        md_io->error = error;
+        device = bio->bi_private;
+        device->md_io.error = error;
 
         /* We grabbed an extra reference in _drbd_md_sync_page_io() to be able
          * to timeout on the lower level device, and eventually detach from it.
@@ -87,7 +84,7 @@ void drbd_md_io_complete(struct bio *bio, int error)
          * ASSERT(atomic_read(&device->md_io_in_use) == 1) there.
          */
         drbd_md_put_buffer(device);
-        md_io->done = 1;
+        device->md_io.done = 1;
         wake_up(&device->misc_wait);
         bio_put(bio);
         if (device->ldev) /* special case: drbd_md_read() during drbd_adm_attach() */
@@ -135,6 +132,7 @@ void drbd_endio_write_sec_final(struct drbd_peer_request *peer_req) __releases(l
         i = peer_req->i;
         do_al_complete_io = peer_req->flags & EE_CALL_AL_COMPLETE_IO;
         block_id = peer_req->block_id;
+        peer_req->flags &= ~EE_CALL_AL_COMPLETE_IO;
 
         spin_lock_irqsave(&device->resource->req_lock, flags);
         device->writ_cnt += peer_req->i.size >> 9;
@@ -398,9 +396,6 @@ static int read_for_csum(struct drbd_peer_device *peer_device, sector_t sector,
         if (!get_ldev(device))
                 return -EIO;
 
-        if (drbd_rs_should_slow_down(device, sector))
-                goto defer;
-
         /* GFP_TRY, because if there is no memory available right now, this may
          * be rescheduled for later. It is "only" background resync, after all. */
         peer_req = drbd_alloc_peer_req(peer_device, ID_SYNCER /* unused */, sector,
@@ -410,7 +405,7 @@ static int read_for_csum(struct drbd_peer_device *peer_device, sector_t sector,
 
         peer_req->w.cb = w_e_send_csum;
         spin_lock_irq(&device->resource->req_lock);
-        list_add(&peer_req->w.list, &device->read_ee);
+        list_add_tail(&peer_req->w.list, &device->read_ee);
         spin_unlock_irq(&device->resource->req_lock);
 
         atomic_add(size >> 9, &device->rs_sect_ev);
@@ -452,9 +447,9 @@ void resync_timer_fn(unsigned long data)
 {
         struct drbd_device *device = (struct drbd_device *) data;
 
-        if (list_empty(&device->resync_work.list))
-                drbd_queue_work(&first_peer_device(device)->connection->sender_work,
-                                &device->resync_work);
+        drbd_queue_work_if_unqueued(
+                &first_peer_device(device)->connection->sender_work,
+                &device->resync_work);
 }
 
 static void fifo_set(struct fifo_buffer *fb, int value)
@@ -504,9 +499,9 @@ struct fifo_buffer *fifo_alloc(int fifo_size)
 static int drbd_rs_controller(struct drbd_device *device, unsigned int sect_in)
 {
         struct disk_conf *dc;
-        unsigned int want;     /* The number of sectors we want in the proxy */
+        unsigned int want;     /* The number of sectors we want in-flight */
         int req_sect; /* Number of sectors to request in this turn */
-        int correction; /* Number of sectors more we need in the proxy*/
+        int correction; /* Number of sectors more we need in-flight */
         int cps; /* correction per invocation of drbd_rs_controller() */
         int steps; /* Number of time steps to plan ahead */
         int curr_corr;
@@ -577,20 +572,27 @@ static int drbd_rs_number_requests(struct drbd_device *device)
          * potentially causing a distributed deadlock on congestion during
          * online-verify or (checksum-based) resync, if max-buffers,
          * socket buffer sizes and resync rate settings are mis-configured. */
-        if (mxb - device->rs_in_flight < number)
-                number = mxb - device->rs_in_flight;
+
+        /* note that "number" is in units of "BM_BLOCK_SIZE" (which is 4k),
+         * mxb (as used here, and in drbd_alloc_pages on the peer) is
+         * "number of pages" (typically also 4k),
+         * but "rs_in_flight" is in "sectors" (512 Byte). */
+        if (mxb - device->rs_in_flight/8 < number)
+                number = mxb - device->rs_in_flight/8;
 
         return number;
 }
 
-static int make_resync_request(struct drbd_device *device, int cancel)
+static int make_resync_request(struct drbd_device *const device, int cancel)
 {
+        struct drbd_peer_device *const peer_device = first_peer_device(device);
+        struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
         unsigned long bit;
         sector_t sector;
         const sector_t capacity = drbd_get_capacity(device->this_bdev);
         int max_bio_size;
         int number, rollback_i, size;
-        int align, queued, sndbuf;
+        int align, requeue = 0;
         int i = 0;
 
         if (unlikely(cancel))
@@ -617,17 +619,22 @@ static int make_resync_request(struct drbd_device *device, int cancel)
                 goto requeue;
 
         for (i = 0; i < number; i++) {
-                /* Stop generating RS requests, when half of the send buffer is filled */
-                mutex_lock(&first_peer_device(device)->connection->data.mutex);
-                if (first_peer_device(device)->connection->data.socket) {
-                        queued = first_peer_device(device)->connection->data.socket->sk->sk_wmem_queued;
-                        sndbuf = first_peer_device(device)->connection->data.socket->sk->sk_sndbuf;
-                } else {
-                        queued = 1;
-                        sndbuf = 0;
-                }
-                mutex_unlock(&first_peer_device(device)->connection->data.mutex);
-                if (queued > sndbuf / 2)
+                /* Stop generating RS requests when half of the send buffer is filled,
+                 * but notify TCP that we'd like to have more space. */
+                mutex_lock(&connection->data.mutex);
+                if (connection->data.socket) {
+                        struct sock *sk = connection->data.socket->sk;
+                        int queued = sk->sk_wmem_queued;
+                        int sndbuf = sk->sk_sndbuf;
+                        if (queued > sndbuf / 2) {
+                                requeue = 1;
+                                if (sk->sk_socket)
+                                        set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+                        }
+                } else
+                        requeue = 1;
+                mutex_unlock(&connection->data.mutex);
+                if (requeue)
                         goto requeue;
 
 next_sector:
@@ -642,8 +649,7 @@ next_sector:
 
                 sector = BM_BIT_TO_SECT(bit);
 
-                if (drbd_rs_should_slow_down(device, sector) ||
-                    drbd_try_rs_begin_io(device, sector)) {
+                if (drbd_try_rs_begin_io(device, sector)) {
                         device->bm_resync_fo = bit;
                         goto requeue;
                 }
@@ -696,9 +702,9 @@ next_sector:
                 /* adjust very last sectors, in case we are oddly sized */
                 if (sector + (size>>9) > capacity)
                         size = (capacity-sector)<<9;
-                if (first_peer_device(device)->connection->agreed_pro_version >= 89 &&
-                    first_peer_device(device)->connection->csums_tfm) {
-                        switch (read_for_csum(first_peer_device(device), sector, size)) {
+
+                if (device->use_csums) {
+                        switch (read_for_csum(peer_device, sector, size)) {
                         case -EIO: /* Disk failure */
                                 put_ldev(device);
                                 return -EIO;
@@ -717,7 +723,7 @@ next_sector:
                         int err;
 
                         inc_rs_pending(device);
-                        err = drbd_send_drequest(first_peer_device(device), P_RS_DATA_REQUEST,
+                        err = drbd_send_drequest(peer_device, P_RS_DATA_REQUEST,
                                                  sector, size, ID_SYNCER);
                         if (err) {
                                 drbd_err(device, "drbd_send_drequest() failed, aborting...\n");
@@ -774,8 +780,7 @@ static int make_ov_request(struct drbd_device *device, int cancel)
 
                 size = BM_BLOCK_SIZE;
 
-                if (drbd_rs_should_slow_down(device, sector) ||
-                    drbd_try_rs_begin_io(device, sector)) {
+                if (drbd_try_rs_begin_io(device, sector)) {
                         device->ov_position = sector;
                         goto requeue;
                 }
@@ -911,7 +916,7 @@ int drbd_resync_finished(struct drbd_device *device)
                 if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T)
                         khelper_cmd = "after-resync-target";
 
-                if (first_peer_device(device)->connection->csums_tfm && device->rs_total) {
+                if (device->use_csums && device->rs_total) {
                         const unsigned long s = device->rs_same_csum;
                         const unsigned long t = device->rs_total;
                         const int ratio =
@@ -1351,13 +1356,15 @@ int w_send_out_of_sync(struct drbd_work *w, int cancel)
 {
         struct drbd_request *req = container_of(w, struct drbd_request, w);
         struct drbd_device *device = req->device;
-        struct drbd_connection *connection = first_peer_device(device)->connection;
+        struct drbd_peer_device *const peer_device = first_peer_device(device);
+        struct drbd_connection *const connection = peer_device->connection;
         int err;
 
         if (unlikely(cancel)) {
                 req_mod(req, SEND_CANCELED);
                 return 0;
         }
+        req->pre_send_jif = jiffies;
 
         /* this time, no connection->send.current_epoch_writes++;
          * If it was sent, it was the closing barrier for the last
@@ -1365,7 +1372,7 @@ int w_send_out_of_sync(struct drbd_work *w, int cancel)
          * No more barriers will be sent, until we leave AHEAD mode again. */
         maybe_send_barrier(connection, req->epoch);
 
-        err = drbd_send_out_of_sync(first_peer_device(device), req);
+        err = drbd_send_out_of_sync(peer_device, req);
         req_mod(req, OOS_HANDED_TO_NETWORK);
 
         return err;
@@ -1380,19 +1387,21 @@ int w_send_dblock(struct drbd_work *w, int cancel)
 {
         struct drbd_request *req = container_of(w, struct drbd_request, w);
         struct drbd_device *device = req->device;
-        struct drbd_connection *connection = first_peer_device(device)->connection;
+        struct drbd_peer_device *const peer_device = first_peer_device(device);
+        struct drbd_connection *connection = peer_device->connection;
         int err;
 
         if (unlikely(cancel)) {
                 req_mod(req, SEND_CANCELED);
                 return 0;
         }
+        req->pre_send_jif = jiffies;
 
         re_init_if_first_write(connection, req->epoch);
         maybe_send_barrier(connection, req->epoch);
         connection->send.current_epoch_writes++;
 
-        err = drbd_send_dblock(first_peer_device(device), req);
+        err = drbd_send_dblock(peer_device, req);
         req_mod(req, err ? SEND_FAILED : HANDED_OVER_TO_NETWORK);
 
         return err;
@@ -1407,19 +1416,21 @@ int w_send_read_req(struct drbd_work *w, int cancel)
 {
         struct drbd_request *req = container_of(w, struct drbd_request, w);
         struct drbd_device *device = req->device;
-        struct drbd_connection *connection = first_peer_device(device)->connection;
+        struct drbd_peer_device *const peer_device = first_peer_device(device);
+        struct drbd_connection *connection = peer_device->connection;
         int err;
 
         if (unlikely(cancel)) {
                 req_mod(req, SEND_CANCELED);
                 return 0;
         }
+        req->pre_send_jif = jiffies;
 
         /* Even read requests may close a write epoch,
          * if there was any yet. */
         maybe_send_barrier(connection, req->epoch);
 
-        err = drbd_send_drequest(first_peer_device(device), P_DATA_REQUEST, req->i.sector, req->i.size,
+        err = drbd_send_drequest(peer_device, P_DATA_REQUEST, req->i.sector, req->i.size,
                                  (unsigned long)req);
 
         req_mod(req, err ? SEND_FAILED : HANDED_OVER_TO_NETWORK);
@@ -1433,7 +1444,7 @@ int w_restart_disk_io(struct drbd_work *w, int cancel)
         struct drbd_device *device = req->device;
 
         if (bio_data_dir(req->master_bio) == WRITE && req->rq_state & RQ_IN_ACT_LOG)
-                drbd_al_begin_io(device, &req->i, false);
+                drbd_al_begin_io(device, &req->i);
 
         drbd_req_make_private_bio(req, req->master_bio);
         req->private_bio->bi_bdev = device->ldev->backing_bdev;
@@ -1601,26 +1612,32 @@ void drbd_rs_controller_reset(struct drbd_device *device)
 void start_resync_timer_fn(unsigned long data)
 {
         struct drbd_device *device = (struct drbd_device *) data;
-
-        drbd_queue_work(&first_peer_device(device)->connection->sender_work,
-                        &device->start_resync_work);
+        drbd_device_post_work(device, RS_START);
 }
 
-int w_start_resync(struct drbd_work *w, int cancel)
+static void do_start_resync(struct drbd_device *device)
 {
-        struct drbd_device *device =
-                container_of(w, struct drbd_device, start_resync_work);
-
         if (atomic_read(&device->unacked_cnt) || atomic_read(&device->rs_pending_cnt)) {
-                drbd_warn(device, "w_start_resync later...\n");
+                drbd_warn(device, "postponing start_resync ...\n");
                 device->start_resync_timer.expires = jiffies + HZ/10;
                 add_timer(&device->start_resync_timer);
-                return 0;
+                return;
         }
 
         drbd_start_resync(device, C_SYNC_SOURCE);
         clear_bit(AHEAD_TO_SYNC_SOURCE, &device->flags);
-        return 0;
+}
+
+static bool use_checksum_based_resync(struct drbd_connection *connection, struct drbd_device *device)
+{
+        bool csums_after_crash_only;
+        rcu_read_lock();
+        csums_after_crash_only = rcu_dereference(connection->net_conf)->csums_after_crash_only;
+        rcu_read_unlock();
+        return connection->agreed_pro_version >= 89 &&          /* supported? */
+                connection->csums_tfm &&                        /* configured? */
+                (csums_after_crash_only == 0                    /* use for each resync? */
+                 || test_bit(CRASHED_PRIMARY, &device->flags)); /* or only after Primary crash? */
 }
 
 /**
@@ -1633,6 +1650,8 @@ int w_start_resync(struct drbd_work *w, int cancel)
  */
 void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
 {
+        struct drbd_peer_device *peer_device = first_peer_device(device);
+        struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
         union drbd_state ns;
         int r;
 
@@ -1651,7 +1670,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
                         if (r > 0) {
                                 drbd_info(device, "before-resync-target handler returned %d, "
                                          "dropping connection.\n", r);
-                                conn_request_state(first_peer_device(device)->connection, NS(conn, C_DISCONNECTING), CS_HARD);
+                                conn_request_state(connection, NS(conn, C_DISCONNECTING), CS_HARD);
                                 return;
                         }
                 } else /* C_SYNC_SOURCE */ {
@@ -1664,7 +1683,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
                                 } else {
                                         drbd_info(device, "before-resync-source handler returned %d, "
                                                  "dropping connection.\n", r);
-                                        conn_request_state(first_peer_device(device)->connection,
+                                        conn_request_state(connection,
                                                            NS(conn, C_DISCONNECTING), CS_HARD);
                                         return;
                                 }
@@ -1672,7 +1691,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
                 }
         }
 
-        if (current == first_peer_device(device)->connection->worker.task) {
+        if (current == connection->worker.task) {
                 /* The worker should not sleep waiting for state_mutex,
                    that can take long */
                 if (!mutex_trylock(device->state_mutex)) {
@@ -1733,11 +1752,20 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
                         device->rs_mark_time[i] = now;
                 }
                 _drbd_pause_after(device);
+                /* Forget potentially stale cached per resync extent bit-counts.
+                 * Open coded drbd_rs_cancel_all(device), we already have IRQs
+                 * disabled, and know the disk state is ok. */
+                spin_lock(&device->al_lock);
+                lc_reset(device->resync);
+                device->resync_locked = 0;
+                device->resync_wenr = LC_FREE;
+                spin_unlock(&device->al_lock);
         }
         write_unlock(&global_state_lock);
         spin_unlock_irq(&device->resource->req_lock);
 
         if (r == SS_SUCCESS) {
+                wake_up(&device->al_wait); /* for lc_reset() above */
                 /* reset rs_last_bcast when a resync or verify is started,
                  * to deal with potential jiffies wrap. */
                 device->rs_last_bcast = jiffies - HZ;
@@ -1746,8 +1774,12 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
                      drbd_conn_str(ns.conn),
                      (unsigned long) device->rs_total << (BM_BLOCK_SHIFT-10),
                      (unsigned long) device->rs_total);
-                if (side == C_SYNC_TARGET)
+                if (side == C_SYNC_TARGET) {
                         device->bm_resync_fo = 0;
+                        device->use_csums = use_checksum_based_resync(connection, device);
+                } else {
+                        device->use_csums = 0;
+                }
 
                 /* Since protocol 96, we must serialize drbd_gen_and_send_sync_uuid
                  * with w_send_oos, or the sync target will get confused as to
@@ -1756,12 +1788,10 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
                  * drbd_resync_finished from here in that case.
                  * We drbd_gen_and_send_sync_uuid here for protocol < 96,
                  * and from after_state_ch otherwise. */
-                if (side == C_SYNC_SOURCE &&
-                    first_peer_device(device)->connection->agreed_pro_version < 96)
-                        drbd_gen_and_send_sync_uuid(first_peer_device(device));
+                if (side == C_SYNC_SOURCE && connection->agreed_pro_version < 96)
+                        drbd_gen_and_send_sync_uuid(peer_device);
 
-                if (first_peer_device(device)->connection->agreed_pro_version < 95 &&
-                    device->rs_total == 0) {
+                if (connection->agreed_pro_version < 95 && device->rs_total == 0) {
                         /* This still has a race (about when exactly the peers
                          * detect connection loss) that can lead to a full sync
                          * on next handshake. In 8.3.9 we fixed this with explicit
@@ -1777,7 +1807,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
                                 int timeo;
 
                                 rcu_read_lock();
-                                nc = rcu_dereference(first_peer_device(device)->connection->net_conf);
+                                nc = rcu_dereference(connection->net_conf);
                                 timeo = nc->ping_int * HZ + nc->ping_timeo * HZ / 9;
                                 rcu_read_unlock();
                                 schedule_timeout_interruptible(timeo);
@@ -1799,10 +1829,165 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
         mutex_unlock(device->state_mutex);
 }
 
+static void update_on_disk_bitmap(struct drbd_device *device, bool resync_done)
+{
+        struct sib_info sib = { .sib_reason = SIB_SYNC_PROGRESS, };
+        device->rs_last_bcast = jiffies;
+
+        if (!get_ldev(device))
+                return;
+
+        drbd_bm_write_lazy(device, 0);
+        if (resync_done && is_sync_state(device->state.conn))
+                drbd_resync_finished(device);
+
+        drbd_bcast_event(device, &sib);
+        /* update timestamp, in case it took a while to write out stuff */
+        device->rs_last_bcast = jiffies;
+        put_ldev(device);
+}
+
+static void drbd_ldev_destroy(struct drbd_device *device)
+{
+        lc_destroy(device->resync);
+        device->resync = NULL;
+        lc_destroy(device->act_log);
+        device->act_log = NULL;
+        __no_warn(local,
+                drbd_free_ldev(device->ldev);
+                device->ldev = NULL;);
+        clear_bit(GOING_DISKLESS, &device->flags);
+        wake_up(&device->misc_wait);
+}
+
+static void go_diskless(struct drbd_device *device)
+{
+        D_ASSERT(device, device->state.disk == D_FAILED);
+        /* we cannot assert local_cnt == 0 here, as get_ldev_if_state will
+         * inc/dec it frequently. Once we are D_DISKLESS, no one will touch
+         * the protected members anymore, though, so once put_ldev reaches zero
+         * again, it will be safe to free them. */
+
+        /* Try to write changed bitmap pages, read errors may have just
+         * set some bits outside the area covered by the activity log.
+         *
+         * If we have an IO error during the bitmap writeout,
+         * we will want a full sync next time, just in case.
+         * (Do we want a specific meta data flag for this?)
+         *
+         * If that does not make it to stable storage either,
+         * we cannot do anything about that anymore.
+         *
+         * We still need to check if both bitmap and ldev are present, we may
+         * end up here after a failed attach, before ldev was even assigned.
+         */
+        if (device->bitmap && device->ldev) {
+                /* An interrupted resync or similar is allowed to recounts bits
+                 * while we detach.
+                 * Any modifications would not be expected anymore, though.
+                 */
+                if (drbd_bitmap_io_from_worker(device, drbd_bm_write,
+                                        "detach", BM_LOCKED_TEST_ALLOWED)) {
+                        if (test_bit(WAS_READ_ERROR, &device->flags)) {
+                                drbd_md_set_flag(device, MDF_FULL_SYNC);
+                                drbd_md_sync(device);
+                        }
+                }
+        }
+
+        drbd_force_state(device, NS(disk, D_DISKLESS));
+}
+
+static int do_md_sync(struct drbd_device *device)
+{
+        drbd_warn(device, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
+        drbd_md_sync(device);
+        return 0;
+}
+
+/* only called from drbd_worker thread, no locking */
+void __update_timing_details(
+                struct drbd_thread_timing_details *tdp,
+                unsigned int *cb_nr,
+                void *cb,
+                const char *fn, const unsigned int line)
+{
+        unsigned int i = *cb_nr % DRBD_THREAD_DETAILS_HIST;
+        struct drbd_thread_timing_details *td = tdp + i;
+
+        td->start_jif = jiffies;
+        td->cb_addr = cb;
+        td->caller_fn = fn;
+        td->line = line;
+        td->cb_nr = *cb_nr;
+
+        i = (i+1) % DRBD_THREAD_DETAILS_HIST;
+        td = tdp + i;
+        memset(td, 0, sizeof(*td));
+
+        ++(*cb_nr);
+}
+
+#define WORK_PENDING(work_bit, todo)    (todo & (1UL << work_bit))
+static void do_device_work(struct drbd_device *device, const unsigned long todo)
+{
+        if (WORK_PENDING(MD_SYNC, todo))
+                do_md_sync(device);
+        if (WORK_PENDING(RS_DONE, todo) ||
+            WORK_PENDING(RS_PROGRESS, todo))
+                update_on_disk_bitmap(device, WORK_PENDING(RS_DONE, todo));
+        if (WORK_PENDING(GO_DISKLESS, todo))
+                go_diskless(device);
+        if (WORK_PENDING(DESTROY_DISK, todo))
+                drbd_ldev_destroy(device);
+        if (WORK_PENDING(RS_START, todo))
+                do_start_resync(device);
+}
+
+#define DRBD_DEVICE_WORK_MASK   \
+        ((1UL << GO_DISKLESS)   \
+        |(1UL << DESTROY_DISK)  \
+        |(1UL << MD_SYNC)       \
+        |(1UL << RS_START)      \
+        |(1UL << RS_PROGRESS)   \
+        |(1UL << RS_DONE)       \
+        )
+
+static unsigned long get_work_bits(unsigned long *flags)
+{
+        unsigned long old, new;
+        do {
+                old = *flags;
+                new = old & ~DRBD_DEVICE_WORK_MASK;
+        } while (cmpxchg(flags, old, new) != old);
+        return old & DRBD_DEVICE_WORK_MASK;
+}
+
+static void do_unqueued_work(struct drbd_connection *connection)
+{
+        struct drbd_peer_device *peer_device;
+        int vnr;
+
+        rcu_read_lock();
+        idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
+                struct drbd_device *device = peer_device->device;
+                unsigned long todo = get_work_bits(&device->flags);
+                if (!todo)
+                        continue;
+
+                kref_get(&device->kref);
+                rcu_read_unlock();
+                do_device_work(device, todo);
+                kref_put(&device->kref, drbd_destroy_device);
+                rcu_read_lock();
+        }
+        rcu_read_unlock();
+}
+
 static bool dequeue_work_batch(struct drbd_work_queue *queue, struct list_head *work_list)
 {
         spin_lock_irq(&queue->q_lock);
-        list_splice_init(&queue->q, work_list);
+        list_splice_tail_init(&queue->q, work_list);
         spin_unlock_irq(&queue->q_lock);
         return !list_empty(work_list);
 }
@@ -1851,7 +2036,7 @@ static void wait_for_work(struct drbd_connection *connection, struct list_head *
                 /* dequeue single item only,
                  * we still use drbd_queue_work_front() in some places */
                 if (!list_empty(&connection->sender_work.q))
-                        list_move(connection->sender_work.q.next, work_list);
+                        list_splice_tail_init(&connection->sender_work.q, work_list);
                 spin_unlock(&connection->sender_work.q_lock);   /* FIXME get rid of this one? */
                 if (!list_empty(work_list) || signal_pending(current)) {
                         spin_unlock_irq(&connection->resource->req_lock);
@@ -1873,6 +2058,14 @@ static void wait_for_work(struct drbd_connection *connection, struct list_head *
                 if (send_barrier)
                         maybe_send_barrier(connection,
                                         connection->send.current_epoch_nr + 1);
+
+                if (test_bit(DEVICE_WORK_PENDING, &connection->flags))
+                        break;
+
+                /* drbd_send() may have called flush_signals() */
+                if (get_t_state(&connection->worker) != RUNNING)
+                        break;
+
                 schedule();
                 /* may be woken up for other things but new work, too,
                  * e.g. if the current epoch got closed.
@@ -1906,10 +2099,15 @@ int drbd_worker(struct drbd_thread *thi)
         while (get_t_state(thi) == RUNNING) {
                 drbd_thread_current_set_cpu(thi);
 
-                /* as long as we use drbd_queue_work_front(),
-                 * we may only dequeue single work items here, not batches. */
-                if (list_empty(&work_list))
+                if (list_empty(&work_list)) {
+                        update_worker_timing_details(connection, wait_for_work);
                         wait_for_work(connection, &work_list);
+                }
+
+                if (test_and_clear_bit(DEVICE_WORK_PENDING, &connection->flags)) {
+                        update_worker_timing_details(connection, do_unqueued_work);
+                        do_unqueued_work(connection);
+                }
 
                 if (signal_pending(current)) {
                         flush_signals(current);
@@ -1926,6 +2124,7 @@ int drbd_worker(struct drbd_thread *thi)
                 while (!list_empty(&work_list)) {
                         w = list_first_entry(&work_list, struct drbd_work, list);
                         list_del_init(&w->list);
+                        update_worker_timing_details(connection, w->cb);
                         if (w->cb(w, connection->cstate < C_WF_REPORT_PARAMS) == 0)
                                 continue;
                         if (connection->cstate >= C_WF_REPORT_PARAMS)
@@ -1934,13 +2133,18 @@ int drbd_worker(struct drbd_thread *thi)
         }
 
         do {
+                if (test_and_clear_bit(DEVICE_WORK_PENDING, &connection->flags)) {
+                        update_worker_timing_details(connection, do_unqueued_work);
+                        do_unqueued_work(connection);
+                }
                 while (!list_empty(&work_list)) {
                         w = list_first_entry(&work_list, struct drbd_work, list);
                         list_del_init(&w->list);
+                        update_worker_timing_details(connection, w->cb);
                         w->cb(w, 1);
                 }
                 dequeue_work_batch(&connection->sender_work, &work_list);
-        } while (!list_empty(&work_list));
+        } while (!list_empty(&work_list) || test_bit(DEVICE_WORK_PENDING, &connection->flags));
 
         rcu_read_lock();
         idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index f63d358f3d93..0a581400de0f 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -15,17 +15,22 @@
 #include <linux/numa.h>
 
 #define PART_BITS 4
+#define VQ_NAME_LEN 16
 
 static int major;
 static DEFINE_IDA(vd_index_ida);
 
 static struct workqueue_struct *virtblk_wq;
 
+struct virtio_blk_vq {
+        struct virtqueue *vq;
+        spinlock_t lock;
+        char name[VQ_NAME_LEN];
+} ____cacheline_aligned_in_smp;
+
 struct virtio_blk
 {
         struct virtio_device *vdev;
-        struct virtqueue *vq;
-        spinlock_t vq_lock;
 
         /* The disk structure for the kernel. */
         struct gendisk *disk;
@@ -47,6 +52,10 @@ struct virtio_blk
 
         /* Ida index - used to track minor number allocations. */
         int index;
+
+        /* num of vqs */
+        int num_vqs;
+        struct virtio_blk_vq *vqs;
 };
 
 struct virtblk_req
@@ -133,14 +142,15 @@ static void virtblk_done(struct virtqueue *vq)
 {
         struct virtio_blk *vblk = vq->vdev->priv;
         bool req_done = false;
+        int qid = vq->index;
         struct virtblk_req *vbr;
         unsigned long flags;
         unsigned int len;
 
-        spin_lock_irqsave(&vblk->vq_lock, flags);
+        spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
         do {
                 virtqueue_disable_cb(vq);
-                while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
+                while ((vbr = virtqueue_get_buf(vblk->vqs[qid].vq, &len)) != NULL) {
                         blk_mq_complete_request(vbr->req);
                         req_done = true;
                 }
@@ -151,7 +161,7 @@ static void virtblk_done(struct virtqueue *vq)
         /* In case queue is stopped waiting for more buffers. */
         if (req_done)
                 blk_mq_start_stopped_hw_queues(vblk->disk->queue, true);
-        spin_unlock_irqrestore(&vblk->vq_lock, flags);
+        spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 }
 
 static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
@@ -160,6 +170,7 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
         struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
         unsigned long flags;
         unsigned int num;
+        int qid = hctx->queue_num;
         const bool last = (req->cmd_flags & REQ_END) != 0;
         int err;
         bool notify = false;
@@ -202,12 +213,12 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
                         vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
         }
 
-        spin_lock_irqsave(&vblk->vq_lock, flags);
-        err = __virtblk_add_req(vblk->vq, vbr, vbr->sg, num);
+        spin_lock_irqsave(&vblk->vqs[qid].lock, flags);
+        err = __virtblk_add_req(vblk->vqs[qid].vq, vbr, vbr->sg, num);
         if (err) {
-                virtqueue_kick(vblk->vq);
+                virtqueue_kick(vblk->vqs[qid].vq);
                 blk_mq_stop_hw_queue(hctx);
-                spin_unlock_irqrestore(&vblk->vq_lock, flags);
+                spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
                 /* Out of mem doesn't actually happen, since we fall back
                  * to direct descriptors */
                 if (err == -ENOMEM || err == -ENOSPC)
@@ -215,12 +226,12 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
                 return BLK_MQ_RQ_QUEUE_ERROR;
         }
 
-        if (last && virtqueue_kick_prepare(vblk->vq))
+        if (last && virtqueue_kick_prepare(vblk->vqs[qid].vq))
                 notify = true;
-        spin_unlock_irqrestore(&vblk->vq_lock, flags);
+        spin_unlock_irqrestore(&vblk->vqs[qid].lock, flags);
 
         if (notify)
-                virtqueue_notify(vblk->vq);
+                virtqueue_notify(vblk->vqs[qid].vq);
         return BLK_MQ_RQ_QUEUE_OK;
 }
 
@@ -377,12 +388,64 @@ static void virtblk_config_changed(struct virtio_device *vdev)
 static int init_vq(struct virtio_blk *vblk)
 {
         int err = 0;
+        int i;
+        vq_callback_t **callbacks;
+        const char **names;
+        struct virtqueue **vqs;
+        unsigned short num_vqs;
+        struct virtio_device *vdev = vblk->vdev;
+
+        err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ,
+                                   struct virtio_blk_config, num_queues,
+                                   &num_vqs);
+        if (err)
+                num_vqs = 1;
+
+        vblk->vqs = kmalloc(sizeof(*vblk->vqs) * num_vqs, GFP_KERNEL);
+        if (!vblk->vqs) {
+                err = -ENOMEM;
+                goto out;
+        }
+
+        names = kmalloc(sizeof(*names) * num_vqs, GFP_KERNEL);
+        if (!names)
+                goto err_names;
+
+        callbacks = kmalloc(sizeof(*callbacks) * num_vqs, GFP_KERNEL);
+        if (!callbacks)
+                goto err_callbacks;
+
+        vqs = kmalloc(sizeof(*vqs) * num_vqs, GFP_KERNEL);
+        if (!vqs)
+                goto err_vqs;
 
-        /* We expect one virtqueue, for output. */
-        vblk->vq = virtio_find_single_vq(vblk->vdev, virtblk_done, "requests");
-        if (IS_ERR(vblk->vq))
-                err = PTR_ERR(vblk->vq);
+        for (i = 0; i < num_vqs; i++) {
+                callbacks[i] = virtblk_done;
+                snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req.%d", i);
+                names[i] = vblk->vqs[i].name;
+        }
+
+        /* Discover virtqueues and write information to configuration.  */
+        err = vdev->config->find_vqs(vdev, num_vqs, vqs, callbacks, names);
+        if (err)
+                goto err_find_vqs;
 
+        for (i = 0; i < num_vqs; i++) {
+                spin_lock_init(&vblk->vqs[i].lock);
+                vblk->vqs[i].vq = vqs[i];
+        }
+        vblk->num_vqs = num_vqs;
+
+ err_find_vqs:
+        kfree(vqs);
+ err_vqs:
+        kfree(callbacks);
+ err_callbacks:
+        kfree(names);
+ err_names:
+        if (err)
+                kfree(vblk->vqs);
+ out:
         return err;
 }
 
@@ -551,7 +614,6 @@ static int virtblk_probe(struct virtio_device *vdev)
         err = init_vq(vblk);
         if (err)
                 goto out_free_vblk;
-        spin_lock_init(&vblk->vq_lock);
 
         /* FIXME: How many partitions?  How long is a piece of string? */
         vblk->disk = alloc_disk(1 << PART_BITS);
@@ -562,7 +624,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 
         /* Default queue sizing is to fill the ring. */
         if (!virtblk_queue_depth) {
-                virtblk_queue_depth = vblk->vq->num_free;
+                virtblk_queue_depth = vblk->vqs[0].vq->num_free;
                 /* ... but without indirect descs, we use 2 descs per req */
                 if (!virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC))
                         virtblk_queue_depth /= 2;
@@ -570,7 +632,6 @@ static int virtblk_probe(struct virtio_device *vdev)
 
         memset(&vblk->tag_set, 0, sizeof(vblk->tag_set));
         vblk->tag_set.ops = &virtio_mq_ops;
-        vblk->tag_set.nr_hw_queues = 1;
         vblk->tag_set.queue_depth = virtblk_queue_depth;
         vblk->tag_set.numa_node = NUMA_NO_NODE;
         vblk->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
@@ -578,6 +639,7 @@ static int virtblk_probe(struct virtio_device *vdev)
                 sizeof(struct virtblk_req) +
                 sizeof(struct scatterlist) * sg_elems;
         vblk->tag_set.driver_data = vblk;
+        vblk->tag_set.nr_hw_queues = vblk->num_vqs;
 
         err = blk_mq_alloc_tag_set(&vblk->tag_set);
         if (err)
@@ -727,6 +789,7 @@ static void virtblk_remove(struct virtio_device *vdev)
         refc = atomic_read(&disk_to_dev(vblk->disk)->kobj.kref.refcount);
         put_disk(vblk->disk);
         vdev->config->del_vqs(vdev);
+        kfree(vblk->vqs);
         kfree(vblk);
 
         /* Only free device id if we don't have any users */
@@ -777,7 +840,8 @@ static const struct virtio_device_id id_table[] = {
 static unsigned int features[] = {
         VIRTIO_BLK_F_SEG_MAX, VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_GEOMETRY,
         VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE, VIRTIO_BLK_F_SCSI,
-        VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE
+        VIRTIO_BLK_F_WCE, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
+        VIRTIO_BLK_F_MQ,
 };
 
 static struct virtio_driver virtio_blk = {