The DRBD driver

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 1484 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
new file mode 100644
index 00000000000..74b4835d310
--- /dev/null
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -0,0 +1,1484 @@
+/*
+   drbd_actlog.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_wrappers.h"
+
+/* We maintain a trivial check sum in our on disk activity log.
+ * With that we can ensure correct operation even when the storage
+ * device might do a partial (last) sector write while loosing power.
+ */
+struct __packed al_transaction {
+        u32       magic;
+        u32       tr_number;
+        struct __packed {
+                u32 pos;
+                u32 extent; } updates[1 + AL_EXTENTS_PT];
+        u32       xor_sum;
+};
+
+struct update_odbm_work {
+        struct drbd_work w;
+        unsigned int enr;
+};
+
+struct update_al_work {
+        struct drbd_work w;
+        struct lc_element *al_ext;
+        struct completion event;
+        unsigned int enr;
+        /* if old_enr != LC_FREE, write corresponding bitmap sector, too */
+        unsigned int old_enr;
+};
+
+struct drbd_atodb_wait {
+        atomic_t           count;
+        struct completion  io_done;
+        struct drbd_conf   *mdev;
+        int                error;
+};
+
+
+int w_al_write_transaction(struct drbd_conf *, struct drbd_work *, int);
+
+/* The actual tracepoint needs to have constant number of known arguments...
+ */
+void trace_drbd_resync(struct drbd_conf *mdev, int level, const char *fmt, ...)
+{
+        va_list ap;
+
+        va_start(ap, fmt);
+        trace__drbd_resync(mdev, level, fmt, ap);
+        va_end(ap);
+}
+
+static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
+                                 struct drbd_backing_dev *bdev,
+                                 struct page *page, sector_t sector,
+                                 int rw, int size)
+{
+        struct bio *bio;
+        struct drbd_md_io md_io;
+        int ok;
+
+        md_io.mdev = mdev;
+        init_completion(&md_io.event);
+        md_io.error = 0;
+
+        if ((rw & WRITE) && !test_bit(MD_NO_BARRIER, &mdev->flags))
+                rw |= (1 << BIO_RW_BARRIER);
+        rw |= ((1<<BIO_RW_UNPLUG) | (1<<BIO_RW_SYNCIO));
+
+ retry:
+        bio = bio_alloc(GFP_NOIO, 1);
+        bio->bi_bdev = bdev->md_bdev;
+        bio->bi_sector = sector;
+        ok = (bio_add_page(bio, page, size, 0) == size);
+        if (!ok)
+                goto out;
+        bio->bi_private = &md_io;
+        bio->bi_end_io = drbd_md_io_complete;
+        bio->bi_rw = rw;
+
+        trace_drbd_bio(mdev, "Md", bio, 0, NULL);
+
+        if (FAULT_ACTIVE(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
+                bio_endio(bio, -EIO);
+        else
+                submit_bio(rw, bio);
+        wait_for_completion(&md_io.event);
+        ok = bio_flagged(bio, BIO_UPTODATE) && md_io.error == 0;
+
+        /* check for unsupported barrier op.
+         * would rather check on EOPNOTSUPP, but that is not reliable.
+         * don't try again for ANY return value != 0 */
+        if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER) && !ok)) {
+                /* Try again with no barrier */
+                dev_warn(DEV, "Barriers not supported on meta data device - disabling\n");
+                set_bit(MD_NO_BARRIER, &mdev->flags);
+                rw &= ~(1 << BIO_RW_BARRIER);
+                bio_put(bio);
+                goto retry;
+        }
+ out:
+        bio_put(bio);
+        return ok;
+}
+
+int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
+                         sector_t sector, int rw)
+{
+        int logical_block_size, mask, ok;
+        int offset = 0;
+        struct page *iop = mdev->md_io_page;
+
+        D_ASSERT(mutex_is_locked(&mdev->md_io_mutex));
+
+        BUG_ON(!bdev->md_bdev);
+
+        logical_block_size = bdev_logical_block_size(bdev->md_bdev);
+        if (logical_block_size == 0)
+                logical_block_size = MD_SECTOR_SIZE;
+
+        /* in case logical_block_size != 512 [ s390 only? ] */
+        if (logical_block_size != MD_SECTOR_SIZE) {
+                mask = (logical_block_size / MD_SECTOR_SIZE) - 1;
+                D_ASSERT(mask == 1 || mask == 3 || mask == 7);
+                D_ASSERT(logical_block_size == (mask+1) * MD_SECTOR_SIZE);
+                offset = sector & mask;
+                sector = sector & ~mask;
+                iop = mdev->md_io_tmpp;
+
+                if (rw & WRITE) {
+                        /* these are GFP_KERNEL pages, pre-allocated
+                         * on device initialization */
+                        void *p = page_address(mdev->md_io_page);
+                        void *hp = page_address(mdev->md_io_tmpp);
+
+                        ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector,
+                                        READ, logical_block_size);
+
+                        if (unlikely(!ok)) {
+                                dev_err(DEV, "drbd_md_sync_page_io(,%llus,"
+                                    "READ [logical_block_size!=512]) failed!\n",
+                                    (unsigned long long)sector);
+                                return 0;
+                        }
+
+                        memcpy(hp + offset*MD_SECTOR_SIZE, p, MD_SECTOR_SIZE);
+                }
+        }
+
+        if (sector < drbd_md_first_sector(bdev) ||
+            sector > drbd_md_last_sector(bdev))
+                dev_alert(DEV, "%s [%d]:%s(,%llus,%s) out of range md access!\n",
+                     current->comm, current->pid, __func__,
+                     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
+
+        ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, logical_block_size);
+        if (unlikely(!ok)) {
+                dev_err(DEV, "drbd_md_sync_page_io(,%llus,%s) failed!\n",
+                    (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
+                return 0;
+        }
+
+        if (logical_block_size != MD_SECTOR_SIZE && !(rw & WRITE)) {
+                void *p = page_address(mdev->md_io_page);
+                void *hp = page_address(mdev->md_io_tmpp);
+
+                memcpy(p, hp + offset*MD_SECTOR_SIZE, MD_SECTOR_SIZE);
+        }
+
+        return ok;
+}
+
+static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr)
+{
+        struct lc_element *al_ext;
+        struct lc_element *tmp;
+        unsigned long     al_flags = 0;
+
+        spin_lock_irq(&mdev->al_lock);
+        tmp = lc_find(mdev->resync, enr/AL_EXT_PER_BM_SECT);
+        if (unlikely(tmp != NULL)) {
+                struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
+                if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
+                        spin_unlock_irq(&mdev->al_lock);
+                        return NULL;
+                }
+        }
+        al_ext   = lc_get(mdev->act_log, enr);
+        al_flags = mdev->act_log->flags;
+        spin_unlock_irq(&mdev->al_lock);
+
+        /*
+        if (!al_ext) {
+                if (al_flags & LC_STARVING)
+                        dev_warn(DEV, "Have to wait for LRU element (AL too small?)\n");
+                if (al_flags & LC_DIRTY)
+                        dev_warn(DEV, "Ongoing AL update (AL device too slow?)\n");
+        }
+        */
+
+        return al_ext;
+}
+
+void drbd_al_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = (sector >> (AL_EXTENT_SHIFT-9));
+        struct lc_element *al_ext;
+        struct update_al_work al_work;
+
+        D_ASSERT(atomic_read(&mdev->local_cnt) > 0);
+
+        trace_drbd_actlog(mdev, sector, "al_begin_io");
+
+        wait_event(mdev->al_wait, (al_ext = _al_get(mdev, enr)));
+
+        if (al_ext->lc_number != enr) {
+                /* drbd_al_write_transaction(mdev,al_ext,enr);
+                 * recurses into generic_make_request(), which
+                 * disallows recursion, bios being serialized on the
+                 * current->bio_tail list now.
+                 * we have to delegate updates to the activity log
+                 * to the worker thread. */
+                init_completion(&al_work.event);
+                al_work.al_ext = al_ext;
+                al_work.enr = enr;
+                al_work.old_enr = al_ext->lc_number;
+                al_work.w.cb = w_al_write_transaction;
+                drbd_queue_work_front(&mdev->data.work, &al_work.w);
+                wait_for_completion(&al_work.event);
+
+                mdev->al_writ_cnt++;
+
+                spin_lock_irq(&mdev->al_lock);
+                lc_changed(mdev->act_log, al_ext);
+                spin_unlock_irq(&mdev->al_lock);
+                wake_up(&mdev->al_wait);
+        }
+}
+
+void drbd_al_complete_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = (sector >> (AL_EXTENT_SHIFT-9));
+        struct lc_element *extent;
+        unsigned long flags;
+
+        trace_drbd_actlog(mdev, sector, "al_complete_io");
+
+        spin_lock_irqsave(&mdev->al_lock, flags);
+
+        extent = lc_find(mdev->act_log, enr);
+
+        if (!extent) {
+                spin_unlock_irqrestore(&mdev->al_lock, flags);
+                dev_err(DEV, "al_complete_io() called on inactive extent %u\n", enr);
+                return;
+        }
+
+        if (lc_put(mdev->act_log, extent) == 0)
+                wake_up(&mdev->al_wait);
+
+        spin_unlock_irqrestore(&mdev->al_lock, flags);
+}
+
+int
+w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        struct update_al_work *aw = container_of(w, struct update_al_work, w);
+        struct lc_element *updated = aw->al_ext;
+        const unsigned int new_enr = aw->enr;
+        const unsigned int evicted = aw->old_enr;
+        struct al_transaction *buffer;
+        sector_t sector;
+        int i, n, mx;
+        unsigned int extent_nr;
+        u32 xor_sum = 0;
+
+        if (!get_ldev(mdev)) {
+                dev_err(DEV, "get_ldev() failed in w_al_write_transaction\n");
+                complete(&((struct update_al_work *)w)->event);
+                return 1;
+        }
+        /* do we have to do a bitmap write, first?
+         * TODO reduce maximum latency:
+         * submit both bios, then wait for both,
+         * instead of doing two synchronous sector writes. */
+        if (mdev->state.conn < C_CONNECTED && evicted != LC_FREE)
+                drbd_bm_write_sect(mdev, evicted/AL_EXT_PER_BM_SECT);
+
+        mutex_lock(&mdev->md_io_mutex); /* protects md_io_page, al_tr_cycle, ... */
+        buffer = (struct al_transaction *)page_address(mdev->md_io_page);
+
+        buffer->magic = __constant_cpu_to_be32(DRBD_MAGIC);
+        buffer->tr_number = cpu_to_be32(mdev->al_tr_number);
+
+        n = lc_index_of(mdev->act_log, updated);
+
+        buffer->updates[0].pos = cpu_to_be32(n);
+        buffer->updates[0].extent = cpu_to_be32(new_enr);
+
+        xor_sum ^= new_enr;
+
+        mx = min_t(int, AL_EXTENTS_PT,
+                   mdev->act_log->nr_elements - mdev->al_tr_cycle);
+        for (i = 0; i < mx; i++) {
+                unsigned idx = mdev->al_tr_cycle + i;
+                extent_nr = lc_element_by_index(mdev->act_log, idx)->lc_number;
+                buffer->updates[i+1].pos = cpu_to_be32(idx);
+                buffer->updates[i+1].extent = cpu_to_be32(extent_nr);
+                xor_sum ^= extent_nr;
+        }
+        for (; i < AL_EXTENTS_PT; i++) {
+                buffer->updates[i+1].pos = __constant_cpu_to_be32(-1);
+                buffer->updates[i+1].extent = __constant_cpu_to_be32(LC_FREE);
+                xor_sum ^= LC_FREE;
+        }
+        mdev->al_tr_cycle += AL_EXTENTS_PT;
+        if (mdev->al_tr_cycle >= mdev->act_log->nr_elements)
+                mdev->al_tr_cycle = 0;
+
+        buffer->xor_sum = cpu_to_be32(xor_sum);
+
+        sector =  mdev->ldev->md.md_offset
+                + mdev->ldev->md.al_offset + mdev->al_tr_pos;
+
+        if (!drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE))
+                drbd_chk_io_error(mdev, 1, TRUE);
+
+        if (++mdev->al_tr_pos >
+            div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
+                mdev->al_tr_pos = 0;
+
+        D_ASSERT(mdev->al_tr_pos < MD_AL_MAX_SIZE);
+        mdev->al_tr_number++;
+
+        mutex_unlock(&mdev->md_io_mutex);
+
+        complete(&((struct update_al_work *)w)->event);
+        put_ldev(mdev);
+
+        return 1;
+}
+
+/**
+ * drbd_al_read_tr() - Read a single transaction from the on disk activity log
+ * @mdev:       DRBD device.
+ * @bdev:       Block device to read form.
+ * @b:          pointer to an al_transaction.
+ * @index:      On disk slot of the transaction to read.
+ *
+ * Returns -1 on IO error, 0 on checksum error and 1 upon success.
+ */
+static int drbd_al_read_tr(struct drbd_conf *mdev,
+                           struct drbd_backing_dev *bdev,
+                           struct al_transaction *b,
+                           int index)
+{
+        sector_t sector;
+        int rv, i;
+        u32 xor_sum = 0;
+
+        sector = bdev->md.md_offset + bdev->md.al_offset + index;
+
+        /* Dont process error normally,
+         * as this is done before disk is attached! */
+        if (!drbd_md_sync_page_io(mdev, bdev, sector, READ))
+                return -1;
+
+        rv = (be32_to_cpu(b->magic) == DRBD_MAGIC);
+
+        for (i = 0; i < AL_EXTENTS_PT + 1; i++)
+                xor_sum ^= be32_to_cpu(b->updates[i].extent);
+        rv &= (xor_sum == be32_to_cpu(b->xor_sum));
+
+        return rv;
+}
+
+/**
+ * drbd_al_read_log() - Restores the activity log from its on disk representation.
+ * @mdev:       DRBD device.
+ * @bdev:       Block device to read form.
+ *
+ * Returns 1 on success, returns 0 when reading the log failed due to IO errors.
+ */
+int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
+{
+        struct al_transaction *buffer;
+        int i;
+        int rv;
+        int mx;
+        int active_extents = 0;
+        int transactions = 0;
+        int found_valid = 0;
+        int from = 0;
+        int to = 0;
+        u32 from_tnr = 0;
+        u32 to_tnr = 0;
+        u32 cnr;
+
+        mx = div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT);
+
+        /* lock out all other meta data io for now,
+         * and make sure the page is mapped.
+         */
+        mutex_lock(&mdev->md_io_mutex);
+        buffer = page_address(mdev->md_io_page);
+
+        /* Find the valid transaction in the log */
+        for (i = 0; i <= mx; i++) {
+                rv = drbd_al_read_tr(mdev, bdev, buffer, i);
+                if (rv == 0)
+                        continue;
+                if (rv == -1) {
+                        mutex_unlock(&mdev->md_io_mutex);
+                        return 0;
+                }
+                cnr = be32_to_cpu(buffer->tr_number);
+
+                if (++found_valid == 1) {
+                        from = i;
+                        to = i;
+                        from_tnr = cnr;
+                        to_tnr = cnr;
+                        continue;
+                }
+                if ((int)cnr - (int)from_tnr < 0) {
+                        D_ASSERT(from_tnr - cnr + i - from == mx+1);
+                        from = i;
+                        from_tnr = cnr;
+                }
+                if ((int)cnr - (int)to_tnr > 0) {
+                        D_ASSERT(cnr - to_tnr == i - to);
+                        to = i;
+                        to_tnr = cnr;
+                }
+        }
+
+        if (!found_valid) {
+                dev_warn(DEV, "No usable activity log found.\n");
+                mutex_unlock(&mdev->md_io_mutex);
+                return 1;
+        }
+
+        /* Read the valid transactions.
+         * dev_info(DEV, "Reading from %d to %d.\n",from,to); */
+        i = from;
+        while (1) {
+                int j, pos;
+                unsigned int extent_nr;
+                unsigned int trn;
+
+                rv = drbd_al_read_tr(mdev, bdev, buffer, i);
+                ERR_IF(rv == 0) goto cancel;
+                if (rv == -1) {
+                        mutex_unlock(&mdev->md_io_mutex);
+                        return 0;
+                }
+
+                trn = be32_to_cpu(buffer->tr_number);
+
+                spin_lock_irq(&mdev->al_lock);
+
+                /* This loop runs backwards because in the cyclic
+                   elements there might be an old version of the
+                   updated element (in slot 0). So the element in slot 0
+                   can overwrite old versions. */
+                for (j = AL_EXTENTS_PT; j >= 0; j--) {
+                        pos = be32_to_cpu(buffer->updates[j].pos);
+                        extent_nr = be32_to_cpu(buffer->updates[j].extent);
+
+                        if (extent_nr == LC_FREE)
+                                continue;
+
+                        lc_set(mdev->act_log, extent_nr, pos);
+                        active_extents++;
+                }
+                spin_unlock_irq(&mdev->al_lock);
+
+                transactions++;
+
+cancel:
+                if (i == to)
+                        break;
+                i++;
+                if (i > mx)
+                        i = 0;
+        }
+
+        mdev->al_tr_number = to_tnr+1;
+        mdev->al_tr_pos = to;
+        if (++mdev->al_tr_pos >
+            div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
+                mdev->al_tr_pos = 0;
+
+        /* ok, we are done with it */
+        mutex_unlock(&mdev->md_io_mutex);
+
+        dev_info(DEV, "Found %d transactions (%d active extents) in activity log.\n",
+             transactions, active_extents);
+
+        return 1;
+}
+
+static void atodb_endio(struct bio *bio, int error)
+{
+        struct drbd_atodb_wait *wc = bio->bi_private;
+        struct drbd_conf *mdev = wc->mdev;
+        struct page *page;
+        int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+        /* strange behavior of some lower level drivers...
+         * fail the request by clearing the uptodate flag,
+         * but do not return any error?! */
+        if (!error && !uptodate)
+                error = -EIO;
+
+        drbd_chk_io_error(mdev, error, TRUE);
+        if (error && wc->error == 0)
+                wc->error = error;
+
+        if (atomic_dec_and_test(&wc->count))
+                complete(&wc->io_done);
+
+        page = bio->bi_io_vec[0].bv_page;
+        put_page(page);
+        bio_put(bio);
+        mdev->bm_writ_cnt++;
+        put_ldev(mdev);
+}
+
+#define S2W(s)  ((s)<<(BM_EXT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
+/* activity log to on disk bitmap -- prepare bio unless that sector
+ * is already covered by previously prepared bios */
+static int atodb_prepare_unless_covered(struct drbd_conf *mdev,
+                                        struct bio **bios,
+                                        unsigned int enr,
+                                        struct drbd_atodb_wait *wc) __must_hold(local)
+{
+        struct bio *bio;
+        struct page *page;
+        sector_t on_disk_sector = enr + mdev->ldev->md.md_offset
+                                      + mdev->ldev->md.bm_offset;
+        unsigned int page_offset = PAGE_SIZE;
+        int offset;
+        int i = 0;
+        int err = -ENOMEM;
+
+        /* Check if that enr is already covered by an already created bio.
+         * Caution, bios[] is not NULL terminated,
+         * but only initialized to all NULL.
+         * For completely scattered activity log,
+         * the last invocation iterates over all bios,
+         * and finds the last NULL entry.
+         */
+        while ((bio = bios[i])) {
+                if (bio->bi_sector == on_disk_sector)
+                        return 0;
+                i++;
+        }
+        /* bios[i] == NULL, the next not yet used slot */
+
+        /* GFP_KERNEL, we are not in the write-out path */
+        bio = bio_alloc(GFP_KERNEL, 1);
+        if (bio == NULL)
+                return -ENOMEM;
+
+        if (i > 0) {
+                const struct bio_vec *prev_bv = bios[i-1]->bi_io_vec;
+                page_offset = prev_bv->bv_offset + prev_bv->bv_len;
+                page = prev_bv->bv_page;
+        }
+        if (page_offset == PAGE_SIZE) {
+                page = alloc_page(__GFP_HIGHMEM);
+                if (page == NULL)
+                        goto out_bio_put;
+                page_offset = 0;
+        } else {
+                get_page(page);
+        }
+
+        offset = S2W(enr);
+        drbd_bm_get_lel(mdev, offset,
+                        min_t(size_t, S2W(1), drbd_bm_words(mdev) - offset),
+                        kmap(page) + page_offset);
+        kunmap(page);
+
+        bio->bi_private = wc;
+        bio->bi_end_io = atodb_endio;
+        bio->bi_bdev = mdev->ldev->md_bdev;
+        bio->bi_sector = on_disk_sector;
+
+        if (bio_add_page(bio, page, MD_SECTOR_SIZE, page_offset) != MD_SECTOR_SIZE)
+                goto out_put_page;
+
+        atomic_inc(&wc->count);
+        /* we already know that we may do this...
+         * get_ldev_if_state(mdev,D_ATTACHING);
+         * just get the extra reference, so that the local_cnt reflects
+         * the number of pending IO requests DRBD at its backing device.
+         */
+        atomic_inc(&mdev->local_cnt);
+
+        bios[i] = bio;
+
+        return 0;
+
+out_put_page:
+        err = -EINVAL;
+        put_page(page);
+out_bio_put:
+        bio_put(bio);
+        return err;
+}
+
+/**
+ * drbd_al_to_on_disk_bm() -  * Writes bitmap parts covered by active AL extents
+ * @mdev:       DRBD device.
+ *
+ * Called when we detach (unconfigure) local storage,
+ * or when we go from R_PRIMARY to R_SECONDARY role.
+ */
+void drbd_al_to_on_disk_bm(struct drbd_conf *mdev)
+{
+        int i, nr_elements;
+        unsigned int enr;
+        struct bio **bios;
+        struct drbd_atodb_wait wc;
+
+        ERR_IF (!get_ldev_if_state(mdev, D_ATTACHING))
+                return; /* sorry, I don't have any act_log etc... */
+
+        wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+
+        nr_elements = mdev->act_log->nr_elements;
+
+        /* GFP_KERNEL, we are not in anyone's write-out path */
+        bios = kzalloc(sizeof(struct bio *) * nr_elements, GFP_KERNEL);
+        if (!bios)
+                goto submit_one_by_one;
+
+        atomic_set(&wc.count, 0);
+        init_completion(&wc.io_done);
+        wc.mdev = mdev;
+        wc.error = 0;
+
+        for (i = 0; i < nr_elements; i++) {
+                enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+                if (enr == LC_FREE)
+                        continue;
+                /* next statement also does atomic_inc wc.count and local_cnt */
+                if (atodb_prepare_unless_covered(mdev, bios,
+                                                enr/AL_EXT_PER_BM_SECT,
+                                                &wc))
+                        goto free_bios_submit_one_by_one;
+        }
+
+        /* unnecessary optimization? */
+        lc_unlock(mdev->act_log);
+        wake_up(&mdev->al_wait);
+
+        /* all prepared, submit them */
+        for (i = 0; i < nr_elements; i++) {
+                if (bios[i] == NULL)
+                        break;
+                if (FAULT_ACTIVE(mdev, DRBD_FAULT_MD_WR)) {
+                        bios[i]->bi_rw = WRITE;
+                        bio_endio(bios[i], -EIO);
+                } else {
+                        submit_bio(WRITE, bios[i]);
+                }
+        }
+
+        drbd_blk_run_queue(bdev_get_queue(mdev->ldev->md_bdev));
+
+        /* always (try to) flush bitmap to stable storage */
+        drbd_md_flush(mdev);
+
+        /* In case we did not submit a single IO do not wait for
+         * them to complete. ( Because we would wait forever here. )
+         *
+         * In case we had IOs and they are already complete, there
+         * is not point in waiting anyways.
+         * Therefore this if () ... */
+        if (atomic_read(&wc.count))
+                wait_for_completion(&wc.io_done);
+
+        put_ldev(mdev);
+
+        kfree(bios);
+        return;
+
+ free_bios_submit_one_by_one:
+        /* free everything by calling the endio callback directly. */
+        for (i = 0; i < nr_elements && bios[i]; i++)
+                bio_endio(bios[i], 0);
+
+        kfree(bios);
+
+ submit_one_by_one:
+        dev_warn(DEV, "Using the slow drbd_al_to_on_disk_bm()\n");
+
+        for (i = 0; i < mdev->act_log->nr_elements; i++) {
+                enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+                if (enr == LC_FREE)
+                        continue;
+                /* Really slow: if we have al-extents 16..19 active,
+                 * sector 4 will be written four times! Synchronous! */
+                drbd_bm_write_sect(mdev, enr/AL_EXT_PER_BM_SECT);
+        }
+
+        lc_unlock(mdev->act_log);
+        wake_up(&mdev->al_wait);
+        put_ldev(mdev);
+}
+
+/**
+ * drbd_al_apply_to_bm() - Sets the bitmap to diry(1) where covered ba active AL extents
+ * @mdev:       DRBD device.
+ */
+void drbd_al_apply_to_bm(struct drbd_conf *mdev)
+{
+        unsigned int enr;
+        unsigned long add = 0;
+        char ppb[10];
+        int i;
+
+        wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+
+        for (i = 0; i < mdev->act_log->nr_elements; i++) {
+                enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+                if (enr == LC_FREE)
+                        continue;
+                add += drbd_bm_ALe_set_all(mdev, enr);
+        }
+
+        lc_unlock(mdev->act_log);
+        wake_up(&mdev->al_wait);
+
+        dev_info(DEV, "Marked additional %s as out-of-sync based on AL.\n",
+             ppsize(ppb, Bit2KB(add)));
+}
+
+static int _try_lc_del(struct drbd_conf *mdev, struct lc_element *al_ext)
+{
+        int rv;
+
+        spin_lock_irq(&mdev->al_lock);
+        rv = (al_ext->refcnt == 0);
+        if (likely(rv))
+                lc_del(mdev->act_log, al_ext);
+        spin_unlock_irq(&mdev->al_lock);
+
+        return rv;
+}
+
+/**
+ * drbd_al_shrink() - Removes all active extents form the activity log
+ * @mdev:       DRBD device.
+ *
+ * Removes all active extents form the activity log, waiting until
+ * the reference count of each entry dropped to 0 first, of course.
+ *
+ * You need to lock mdev->act_log with lc_try_lock() / lc_unlock()
+ */
+void drbd_al_shrink(struct drbd_conf *mdev)
+{
+        struct lc_element *al_ext;
+        int i;
+
+        D_ASSERT(test_bit(__LC_DIRTY, &mdev->act_log->flags));
+
+        for (i = 0; i < mdev->act_log->nr_elements; i++) {
+                al_ext = lc_element_by_index(mdev->act_log, i);
+                if (al_ext->lc_number == LC_FREE)
+                        continue;
+                wait_event(mdev->al_wait, _try_lc_del(mdev, al_ext));
+        }
+
+        wake_up(&mdev->al_wait);
+}
+
+static int w_update_odbm(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        struct update_odbm_work *udw = container_of(w, struct update_odbm_work, w);
+
+        if (!get_ldev(mdev)) {
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_warn(DEV, "Can not update on disk bitmap, local IO disabled.\n");
+                kfree(udw);
+                return 1;
+        }
+
+        drbd_bm_write_sect(mdev, udw->enr);
+        put_ldev(mdev);
+
+        kfree(udw);
+
+        if (drbd_bm_total_weight(mdev) <= mdev->rs_failed) {
+                switch (mdev->state.conn) {
+                case C_SYNC_SOURCE:  case C_SYNC_TARGET:
+                case C_PAUSED_SYNC_S: case C_PAUSED_SYNC_T:
+                        drbd_resync_finished(mdev);
+                default:
+                        /* nothing to do */
+                        break;
+                }
+        }
+        drbd_bcast_sync_progress(mdev);
+
+        return 1;
+}
+
+
+/* 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.
+ *
+ * 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_conf *mdev, sector_t sector,
+                                      int count, int success)
+{
+        struct lc_element *e;
+        struct update_odbm_work *udw;
+
+        unsigned int enr;
+
+        D_ASSERT(atomic_read(&mdev->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(mdev->resync, enr);
+        if (e) {
+                struct bm_extent *ext = lc_entry(e, struct bm_extent, lce);
+                if (ext->lce.lc_number == enr) {
+                        if (success)
+                                ext->rs_left -= count;
+                        else
+                                ext->rs_failed += count;
+                        if (ext->rs_left < ext->rs_failed) {
+                                dev_err(DEV, "BAD! sector=%llus enr=%u rs_left=%d "
+                                    "rs_failed=%d count=%d\n",
+                                     (unsigned long long)sector,
+                                     ext->lce.lc_number, ext->rs_left,
+                                     ext->rs_failed, count);
+                                dump_stack();
+
+                                lc_put(mdev->resync, &ext->lce);
+                                drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                                return;
+                        }
+                } else {
+                        /* Normally this element should be in the cache,
+                         * since drbd_rs_begin_io() pulled it already in.
+                         *
+                         * But maybe an application write finished, and we set
+                         * something outside the resync lru_cache in sync.
+                         */
+                        int rs_left = drbd_bm_e_weight(mdev, enr);
+                        if (ext->flags != 0) {
+                                dev_warn(DEV, "changing resync lce: %d[%u;%02lx]"
+                                     " -> %d[%u;00]\n",
+                                     ext->lce.lc_number, ext->rs_left,
+                                     ext->flags, enr, rs_left);
+                                ext->flags = 0;
+                        }
+                        if (ext->rs_failed) {
+                                dev_warn(DEV, "Kicking resync_lru element enr=%u "
+                                     "out with rs_failed=%d\n",
+                                     ext->lce.lc_number, ext->rs_failed);
+                                set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
+                        }
+                        ext->rs_left = rs_left;
+                        ext->rs_failed = success ? 0 : count;
+                        lc_changed(mdev->resync, &ext->lce);
+                }
+                lc_put(mdev->resync, &ext->lce);
+                /* no race, we are within the al_lock! */
+
+                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;
+                                drbd_queue_work_front(&mdev->data.work, &udw->w);
+                        } else {
+                                dev_warn(DEV, "Could not kmalloc an udw\n");
+                                set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
+                        }
+                }
+        } else {
+                dev_err(DEV, "lc_get() failed! locked=%d/%d flags=%lu\n",
+                    mdev->resync_locked,
+                    mdev->resync->nr_elements,
+                    mdev->resync->flags);
+        }
+}
+
+/* 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_conf *mdev, sector_t sector, int size,
+                       const char *file, const unsigned int line)
+{
+        /* 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;
+
+        if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+                dev_err(DEV, "drbd_set_in_sync: sector=%llus size=%d nonsense!\n",
+                                (unsigned long long)sector, size);
+                return;
+        }
+        nr_sectors = drbd_get_capacity(mdev->this_bdev);
+        esector = sector + (size >> 9) - 1;
+
+        ERR_IF(sector >= nr_sectors) return;
+        ERR_IF(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))
+                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);
+
+        trace_drbd_resync(mdev, TRACE_LVL_METRICS,
+                          "drbd_set_in_sync: sector=%llus size=%u sbnr=%lu ebnr=%lu\n",
+                          (unsigned long long)sector, size, sbnr, ebnr);
+
+        if (sbnr > ebnr)
+                return;
+
+        /*
+         * ok, (capacity & 7) != 0 sometimes, but who cares...
+         * we count rs_{total,left} in bits, not sectors.
+         */
+        spin_lock_irqsave(&mdev->al_lock, flags);
+        count = drbd_bm_clear_bits(mdev, sbnr, ebnr);
+        if (count) {
+                /* we need the lock for drbd_try_clear_on_disk_bm */
+                if (jiffies - mdev->rs_mark_time > HZ*10) {
+                        /* should be rolling marks,
+                         * but we estimate only anyways. */
+                        if (mdev->rs_mark_left != drbd_bm_total_weight(mdev) &&
+                            mdev->state.conn != C_PAUSED_SYNC_T &&
+                            mdev->state.conn != C_PAUSED_SYNC_S) {
+                                mdev->rs_mark_time = jiffies;
+                                mdev->rs_mark_left = drbd_bm_total_weight(mdev);
+                        }
+                }
+                if (get_ldev(mdev)) {
+                        drbd_try_clear_on_disk_bm(mdev, sector, count, TRUE);
+                        put_ldev(mdev);
+                }
+                /* just wake_up unconditional now, various lc_chaged(),
+                 * lc_put() in drbd_try_clear_on_disk_bm(). */
+                wake_up = 1;
+        }
+        spin_unlock_irqrestore(&mdev->al_lock, flags);
+        if (wake_up)
+                wake_up(&mdev->al_wait);
+}
+
+/*
+ * this is intended to set one request worth of data out of sync.
+ * affects at least 1 bit,
+ * and at most 1+DRBD_MAX_SEGMENT_SIZE/BM_BLOCK_SIZE bits.
+ *
+ * called by tl_clear and drbd_send_dblock (==drbd_make_request).
+ * so this can be _any_ process.
+ */
+void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector, int size,
+                            const char *file, const unsigned int line)
+{
+        unsigned long sbnr, ebnr, lbnr, flags;
+        sector_t esector, nr_sectors;
+        unsigned int enr, count;
+        struct lc_element *e;
+
+        if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+                dev_err(DEV, "sector: %llus, size: %d\n",
+                        (unsigned long long)sector, size);
+                return;
+        }
+
+        if (!get_ldev(mdev))
+                return; /* no disk, no metadata, no bitmap to set bits in */
+
+        nr_sectors = drbd_get_capacity(mdev->this_bdev);
+        esector = sector + (size >> 9) - 1;
+
+        ERR_IF(sector >= nr_sectors)
+                goto out;
+        ERR_IF(esector >= nr_sectors)
+                esector = (nr_sectors-1);
+
+        lbnr = BM_SECT_TO_BIT(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);
+
+        trace_drbd_resync(mdev, TRACE_LVL_METRICS,
+                          "drbd_set_out_of_sync: sector=%llus size=%u sbnr=%lu ebnr=%lu\n",
+                          (unsigned long long)sector, size, sbnr, ebnr);
+
+        /* ok, (capacity & 7) != 0 sometimes, but who cares...
+         * we count rs_{total,left} in bits, not sectors.  */
+        spin_lock_irqsave(&mdev->al_lock, flags);
+        count = drbd_bm_set_bits(mdev, sbnr, ebnr);
+
+        enr = BM_SECT_TO_EXT(sector);
+        e = lc_find(mdev->resync, enr);
+        if (e)
+                lc_entry(e, struct bm_extent, lce)->rs_left += count;
+        spin_unlock_irqrestore(&mdev->al_lock, flags);
+
+out:
+        put_ldev(mdev);
+}
+
+static
+struct bm_extent *_bme_get(struct drbd_conf *mdev, unsigned int enr)
+{
+        struct lc_element *e;
+        struct bm_extent *bm_ext;
+        int wakeup = 0;
+        unsigned long rs_flags;
+
+        spin_lock_irq(&mdev->al_lock);
+        if (mdev->resync_locked > mdev->resync->nr_elements/2) {
+                spin_unlock_irq(&mdev->al_lock);
+                return NULL;
+        }
+        e = lc_get(mdev->resync, enr);
+        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+        if (bm_ext) {
+                if (bm_ext->lce.lc_number != enr) {
+                        bm_ext->rs_left = drbd_bm_e_weight(mdev, enr);
+                        bm_ext->rs_failed = 0;
+                        lc_changed(mdev->resync, &bm_ext->lce);
+                        wakeup = 1;
+                }
+                if (bm_ext->lce.refcnt == 1)
+                        mdev->resync_locked++;
+                set_bit(BME_NO_WRITES, &bm_ext->flags);
+        }
+        rs_flags = mdev->resync->flags;
+        spin_unlock_irq(&mdev->al_lock);
+        if (wakeup)
+                wake_up(&mdev->al_wait);
+
+        if (!bm_ext) {
+                if (rs_flags & LC_STARVING)
+                        dev_warn(DEV, "Have to wait for element"
+                             " (resync LRU too small?)\n");
+                BUG_ON(rs_flags & LC_DIRTY);
+        }
+
+        return bm_ext;
+}
+
+static int _is_in_al(struct drbd_conf *mdev, unsigned int enr)
+{
+        struct lc_element *al_ext;
+        int rv = 0;
+
+        spin_lock_irq(&mdev->al_lock);
+        if (unlikely(enr == mdev->act_log->new_number))
+                rv = 1;
+        else {
+                al_ext = lc_find(mdev->act_log, enr);
+                if (al_ext) {
+                        if (al_ext->refcnt)
+                                rv = 1;
+                }
+        }
+        spin_unlock_irq(&mdev->al_lock);
+
+        /*
+        if (unlikely(rv)) {
+                dev_info(DEV, "Delaying sync read until app's write is done\n");
+        }
+        */
+        return rv;
+}
+
+/**
+ * drbd_rs_begin_io() - Gets an extent in the resync LRU cache and sets it to BME_LOCKED
+ * @mdev:       DRBD device.
+ * @sector:     The sector number.
+ *
+ * This functions sleeps on al_wait. Returns 1 on success, 0 if interrupted.
+ */
+int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = BM_SECT_TO_EXT(sector);
+        struct bm_extent *bm_ext;
+        int i, sig;
+
+        trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                          "drbd_rs_begin_io: sector=%llus (rs_end=%d)\n",
+                          (unsigned long long)sector, enr);
+
+        sig = wait_event_interruptible(mdev->al_wait,
+                        (bm_ext = _bme_get(mdev, enr)));
+        if (sig)
+                return 0;
+
+        if (test_bit(BME_LOCKED, &bm_ext->flags))
+                return 1;
+
+        for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
+                sig = wait_event_interruptible(mdev->al_wait,
+                                !_is_in_al(mdev, enr * AL_EXT_PER_BM_SECT + i));
+                if (sig) {
+                        spin_lock_irq(&mdev->al_lock);
+                        if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
+                                clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                                mdev->resync_locked--;
+                                wake_up(&mdev->al_wait);
+                        }
+                        spin_unlock_irq(&mdev->al_lock);
+                        return 0;
+                }
+        }
+
+        set_bit(BME_LOCKED, &bm_ext->flags);
+
+        return 1;
+}
+
+/**
+ * drbd_try_rs_begin_io() - Gets an extent in the resync LRU cache, does not sleep
+ * @mdev:       DRBD device.
+ * @sector:     The sector number.
+ *
+ * Gets an extent in the resync LRU cache, sets it to BME_NO_WRITES, then
+ * tries to set it to BME_LOCKED. Returns 0 upon success, and -EAGAIN
+ * if there is still application IO going on in this area.
+ */
+int drbd_try_rs_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = BM_SECT_TO_EXT(sector);
+        const unsigned int al_enr = enr*AL_EXT_PER_BM_SECT;
+        struct lc_element *e;
+        struct bm_extent *bm_ext;
+        int i;
+
+        trace_drbd_resync(mdev, TRACE_LVL_ALL, "drbd_try_rs_begin_io: sector=%llus\n",
+                          (unsigned long long)sector);
+
+        spin_lock_irq(&mdev->al_lock);
+        if (mdev->resync_wenr != LC_FREE && mdev->resync_wenr != enr) {
+                /* in case you have very heavy scattered io, it may
+                 * stall the syncer undefined if we give up the ref count
+                 * when we try again and requeue.
+                 *
+                 * if we don't give up the refcount, but the next time
+                 * we are scheduled this extent has been "synced" by new
+                 * application writes, we'd miss the lc_put on the
+                 * extent we keep the refcount on.
+                 * so we remembered which extent we had to try again, and
+                 * if the next requested one is something else, we do
+                 * the lc_put here...
+                 * we also have to wake_up
+                 */
+
+                trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                                  "dropping %u, apparently got 'synced' by application io\n",
+                                  mdev->resync_wenr);
+
+                e = lc_find(mdev->resync, mdev->resync_wenr);
+                bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+                if (bm_ext) {
+                        D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+                        D_ASSERT(test_bit(BME_NO_WRITES, &bm_ext->flags));
+                        clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                        mdev->resync_wenr = LC_FREE;
+                        if (lc_put(mdev->resync, &bm_ext->lce) == 0)
+                                mdev->resync_locked--;
+                        wake_up(&mdev->al_wait);
+                } else {
+                        dev_alert(DEV, "LOGIC BUG\n");
+                }
+        }
+        /* TRY. */
+        e = lc_try_get(mdev->resync, enr);
+        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+        if (bm_ext) {
+                if (test_bit(BME_LOCKED, &bm_ext->flags))
+                        goto proceed;
+                if (!test_and_set_bit(BME_NO_WRITES, &bm_ext->flags)) {
+                        mdev->resync_locked++;
+                } else {
+                        /* we did set the BME_NO_WRITES,
+                         * but then could not set BME_LOCKED,
+                         * so we tried again.
+                         * drop the extra reference. */
+                        trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                                          "dropping extra reference on %u\n", enr);
+
+                        bm_ext->lce.refcnt--;
+                        D_ASSERT(bm_ext->lce.refcnt > 0);
+                }
+                goto check_al;
+        } else {
+                /* do we rather want to try later? */
+                if (mdev->resync_locked > mdev->resync->nr_elements-3) {
+                        trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                                          "resync_locked = %u!\n", mdev->resync_locked);
+
+                        goto try_again;
+                }
+                /* Do or do not. There is no try. -- Yoda */
+                e = lc_get(mdev->resync, enr);
+                bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+                if (!bm_ext) {
+                        const unsigned long rs_flags = mdev->resync->flags;
+                        if (rs_flags & LC_STARVING)
+                                dev_warn(DEV, "Have to wait for element"
+                                     " (resync LRU too small?)\n");
+                        BUG_ON(rs_flags & LC_DIRTY);
+                        goto try_again;
+                }
+                if (bm_ext->lce.lc_number != enr) {
+                        bm_ext->rs_left = drbd_bm_e_weight(mdev, enr);
+                        bm_ext->rs_failed = 0;
+                        lc_changed(mdev->resync, &bm_ext->lce);
+                        wake_up(&mdev->al_wait);
+                        D_ASSERT(test_bit(BME_LOCKED, &bm_ext->flags) == 0);
+                }
+                set_bit(BME_NO_WRITES, &bm_ext->flags);
+                D_ASSERT(bm_ext->lce.refcnt == 1);
+                mdev->resync_locked++;
+                goto check_al;
+        }
+check_al:
+        trace_drbd_resync(mdev, TRACE_LVL_ALL, "checking al for %u\n", enr);
+
+        for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
+                if (unlikely(al_enr+i == mdev->act_log->new_number))
+                        goto try_again;
+                if (lc_is_used(mdev->act_log, al_enr+i))
+                        goto try_again;
+        }
+        set_bit(BME_LOCKED, &bm_ext->flags);
+proceed:
+        mdev->resync_wenr = LC_FREE;
+        spin_unlock_irq(&mdev->al_lock);
+        return 0;
+
+try_again:
+        trace_drbd_resync(mdev, TRACE_LVL_ALL, "need to try again for %u\n", enr);
+        if (bm_ext)
+                mdev->resync_wenr = enr;
+        spin_unlock_irq(&mdev->al_lock);
+        return -EAGAIN;
+}
+
+void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = BM_SECT_TO_EXT(sector);
+        struct lc_element *e;
+        struct bm_extent *bm_ext;
+        unsigned long flags;
+
+        trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                          "drbd_rs_complete_io: sector=%llus (rs_enr=%d)\n",
+                          (long long)sector, enr);
+
+        spin_lock_irqsave(&mdev->al_lock, flags);
+        e = lc_find(mdev->resync, enr);
+        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+        if (!bm_ext) {
+                spin_unlock_irqrestore(&mdev->al_lock, flags);
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "drbd_rs_complete_io() called, but extent not found\n");
+                return;
+        }
+
+        if (bm_ext->lce.refcnt == 0) {
+                spin_unlock_irqrestore(&mdev->al_lock, flags);
+                dev_err(DEV, "drbd_rs_complete_io(,%llu [=%u]) called, "
+                    "but refcnt is 0!?\n",
+                    (unsigned long long)sector, enr);
+                return;
+        }
+
+        if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
+                clear_bit(BME_LOCKED, &bm_ext->flags);
+                clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                mdev->resync_locked--;
+                wake_up(&mdev->al_wait);
+        }
+
+        spin_unlock_irqrestore(&mdev->al_lock, flags);
+}
+
+/**
+ * drbd_rs_cancel_all() - Removes all extents from the resync LRU (even BME_LOCKED)
+ * @mdev:       DRBD device.
+ */
+void drbd_rs_cancel_all(struct drbd_conf *mdev)
+{
+        trace_drbd_resync(mdev, TRACE_LVL_METRICS, "drbd_rs_cancel_all\n");
+
+        spin_lock_irq(&mdev->al_lock);
+
+        if (get_ldev_if_state(mdev, D_FAILED)) { /* Makes sure ->resync is there. */
+                lc_reset(mdev->resync);
+                put_ldev(mdev);
+        }
+        mdev->resync_locked = 0;
+        mdev->resync_wenr = LC_FREE;
+        spin_unlock_irq(&mdev->al_lock);
+        wake_up(&mdev->al_wait);
+}
+
+/**
+ * drbd_rs_del_all() - Gracefully remove all extents from the resync LRU
+ * @mdev:       DRBD device.
+ *
+ * Returns 0 upon success, -EAGAIN if at least one reference count was
+ * not zero.
+ */
+int drbd_rs_del_all(struct drbd_conf *mdev)
+{
+        struct lc_element *e;
+        struct bm_extent *bm_ext;
+        int i;
+
+        trace_drbd_resync(mdev, TRACE_LVL_METRICS, "drbd_rs_del_all\n");
+
+        spin_lock_irq(&mdev->al_lock);
+
+        if (get_ldev_if_state(mdev, D_FAILED)) {
+                /* ok, ->resync is there. */
+                for (i = 0; i < mdev->resync->nr_elements; i++) {
+                        e = lc_element_by_index(mdev->resync, i);
+                        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+                        if (bm_ext->lce.lc_number == LC_FREE)
+                                continue;
+                        if (bm_ext->lce.lc_number == mdev->resync_wenr) {
+                                dev_info(DEV, "dropping %u in drbd_rs_del_all, apparently"
+                                     " got 'synced' by application io\n",
+                                     mdev->resync_wenr);
+                                D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+                                D_ASSERT(test_bit(BME_NO_WRITES, &bm_ext->flags));
+                                clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                                mdev->resync_wenr = LC_FREE;
+                                lc_put(mdev->resync, &bm_ext->lce);
+                        }
+                        if (bm_ext->lce.refcnt != 0) {
+                                dev_info(DEV, "Retrying drbd_rs_del_all() later. "
+                                     "refcnt=%d\n", bm_ext->lce.refcnt);
+                                put_ldev(mdev);
+                                spin_unlock_irq(&mdev->al_lock);
+                                return -EAGAIN;
+                        }
+                        D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+                        D_ASSERT(!test_bit(BME_NO_WRITES, &bm_ext->flags));
+                        lc_del(mdev->resync, &bm_ext->lce);
+                }
+                D_ASSERT(mdev->resync->used == 0);
+                put_ldev(mdev);
+        }
+        spin_unlock_irq(&mdev->al_lock);
+
+        return 0;
+}
+
+/**
+ * drbd_rs_failed_io() - Record information on a failure to resync the specified blocks
+ * @mdev:       DRBD device.
+ * @sector:     The sector number.
+ * @size:       Size of failed IO operation, in byte.
+ */
+void drbd_rs_failed_io(struct drbd_conf *mdev, 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;
+
+        trace_drbd_resync(mdev, TRACE_LVL_SUMMARY,
+                          "drbd_rs_failed_io: sector=%llus, size=%u\n",
+                          (unsigned long long)sector, size);
+
+        if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+                dev_err(DEV, "drbd_rs_failed_io: sector=%llus size=%d nonsense!\n",
+                                (unsigned long long)sector, size);
+                return;
+        }
+        nr_sectors = drbd_get_capacity(mdev->this_bdev);
+        esector = sector + (size >> 9) - 1;
+
+        ERR_IF(sector >= nr_sectors) return;
+        ERR_IF(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(&mdev->al_lock);
+        count = drbd_bm_count_bits(mdev, sbnr, ebnr);
+        if (count) {
+                mdev->rs_failed += count;
+
+                if (get_ldev(mdev)) {
+                        drbd_try_clear_on_disk_bm(mdev, sector, count, FALSE);
+                        put_ldev(mdev);
+                }
+
+                /* just wake_up unconditional now, various lc_chaged(),
+                 * lc_put() in drbd_try_clear_on_disk_bm(). */
+                wake_up = 1;
+        }
+        spin_unlock_irq(&mdev->al_lock);
+        if (wake_up)
+                wake_up(&mdev->al_wait);
+}