Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block

* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
  block: Don't count_vm_events for discard bio in submit_bio.
  cfq: fix recursive call in cfq_blkiocg_update_completion_stats()
  cfq-iosched: Fixed boot warning with BLK_CGROUP=y and CFQ_GROUP_IOSCHED=n
  cfq: Don't allow queue merges for queues that have no process references
  block: fix DISCARD_BARRIER requests
  cciss: set SCSI max cmd len to 16, as default is wrong
  cpqarray: fix two more wrong section type
  cpqarray: fix wrong __init type on pci probe function
  drbd: Fixed a race between disk-attach and unexpected state changes
  writeback: fix pin_sb_for_writeback
  writeback: add missing requeue_io in writeback_inodes_wb
  writeback: simplify and split bdi_start_writeback
  writeback: simplify wakeup_flusher_threads
  writeback: fix writeback_inodes_wb from writeback_inodes_sb
  writeback: enforce s_umount locking in writeback_inodes_sb
  writeback: queue work on stack in writeback_inodes_sb
  writeback: fix writeback completion notifications

12 files changed, 280 insertions, 193 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index f84cce42fc58..f0640d7f800f 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1149,13 +1149,10 @@ void init_request_from_bio(struct request *req, struct bio *bio)
         else
                 req->cmd_flags |= bio->bi_rw & REQ_FAILFAST_MASK;
 
-        if (unlikely(bio_rw_flagged(bio, BIO_RW_DISCARD))) {
+        if (bio_rw_flagged(bio, BIO_RW_DISCARD))
                 req->cmd_flags |= REQ_DISCARD;
-                if (bio_rw_flagged(bio, BIO_RW_BARRIER))
-                        req->cmd_flags |= REQ_SOFTBARRIER;
-        } else if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER)))
+        if (bio_rw_flagged(bio, BIO_RW_BARRIER))
                 req->cmd_flags |= REQ_HARDBARRIER;
-
         if (bio_rw_flagged(bio, BIO_RW_SYNCIO))
                 req->cmd_flags |= REQ_RW_SYNC;
         if (bio_rw_flagged(bio, BIO_RW_META))
@@ -1586,7 +1583,7 @@ void submit_bio(int rw, struct bio *bio)
          * If it's a regular read/write or a barrier with data attached,
          * go through the normal accounting stuff before submission.
          */
-        if (bio_has_data(bio)) {
+        if (bio_has_data(bio) && !(rw & (1 << BIO_RW_DISCARD))) {
                 if (rw & WRITE) {
                         count_vm_events(PGPGOUT, count);
                 } else {
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 5ff4f4850e71..7982b830db58 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -14,7 +14,7 @@
 #include <linux/rbtree.h>
 #include <linux/ioprio.h>
 #include <linux/blktrace_api.h>
-#include "blk-cgroup.h"
+#include "cfq.h"
 
 /*
  * tunables
@@ -879,7 +879,7 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
         if (!RB_EMPTY_NODE(&cfqg->rb_node))
                 cfq_rb_erase(&cfqg->rb_node, st);
         cfqg->saved_workload_slice = 0;
-        blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
+        cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
 }
 
 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
@@ -939,8 +939,8 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
 
         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
                                         st->min_vdisktime);
-        blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
-        blkiocg_set_start_empty_time(&cfqg->blkg);
+        cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl);
+        cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
 }
 
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
@@ -995,7 +995,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
 
         /* Add group onto cgroup list */
         sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
-        blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
+        cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
                                         MKDEV(major, minor));
         cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
 
@@ -1079,7 +1079,7 @@ static void cfq_release_cfq_groups(struct cfq_data *cfqd)
                  * it from cgroup list, then it will take care of destroying
                  * cfqg also.
                  */
-                if (!blkiocg_del_blkio_group(&cfqg->blkg))
+                if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg))
                         cfq_destroy_cfqg(cfqd, cfqg);
         }
 }
@@ -1421,10 +1421,10 @@ static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
 {
         elv_rb_del(&cfqq->sort_list, rq);
         cfqq->queued[rq_is_sync(rq)]--;
-        blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg, rq_data_dir(rq),
-                                                rq_is_sync(rq));
+        cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
+                                        rq_data_dir(rq), rq_is_sync(rq));
         cfq_add_rq_rb(rq);
-        blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
+        cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
                         &cfqq->cfqd->serving_group->blkg, rq_data_dir(rq),
                         rq_is_sync(rq));
 }
@@ -1482,8 +1482,8 @@ static void cfq_remove_request(struct request *rq)
         cfq_del_rq_rb(rq);
 
         cfqq->cfqd->rq_queued--;
-        blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg, rq_data_dir(rq),
-                                                rq_is_sync(rq));
+        cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
+                                        rq_data_dir(rq), rq_is_sync(rq));
         if (rq_is_meta(rq)) {
                 WARN_ON(!cfqq->meta_pending);
                 cfqq->meta_pending--;
@@ -1518,8 +1518,8 @@ static void cfq_merged_request(struct request_queue *q, struct request *req,
 static void cfq_bio_merged(struct request_queue *q, struct request *req,
                                 struct bio *bio)
 {
-        blkiocg_update_io_merged_stats(&(RQ_CFQG(req))->blkg, bio_data_dir(bio),
-                                        cfq_bio_sync(bio));
+        cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(req))->blkg,
+                                        bio_data_dir(bio), cfq_bio_sync(bio));
 }
 
 static void
@@ -1539,8 +1539,8 @@ cfq_merged_requests(struct request_queue *q, struct request *rq,
         if (cfqq->next_rq == next)
                 cfqq->next_rq = rq;
         cfq_remove_request(next);
-        blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg, rq_data_dir(next),
-                                        rq_is_sync(next));
+        cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg,
+                                        rq_data_dir(next), rq_is_sync(next));
 }
 
 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
@@ -1571,7 +1571,7 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
 static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         del_timer(&cfqd->idle_slice_timer);
-        blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
+        cfq_blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
 }
 
 static void __cfq_set_active_queue(struct cfq_data *cfqd,
@@ -1580,7 +1580,7 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
         if (cfqq) {
                 cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
                                 cfqd->serving_prio, cfqd->serving_type);
-                blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
+                cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
                 cfqq->slice_start = 0;
                 cfqq->dispatch_start = jiffies;
                 cfqq->allocated_slice = 0;
@@ -1911,7 +1911,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
         sl = cfqd->cfq_slice_idle;
 
         mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
-        blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
+        cfq_blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
         cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
 }
 
@@ -1931,7 +1931,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
         elv_dispatch_sort(q, rq);
 
         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
-        blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
+        cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
                                         rq_data_dir(rq), rq_is_sync(rq));
 }
 
@@ -1986,6 +1986,15 @@ static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
         int process_refs, new_process_refs;
         struct cfq_queue *__cfqq;
 
+        /*
+         * If there are no process references on the new_cfqq, then it is
+         * unsafe to follow the ->new_cfqq chain as other cfqq's in the
+         * chain may have dropped their last reference (not just their
+         * last process reference).
+         */
+        if (!cfqq_process_refs(new_cfqq))
+                return;
+
         /* Avoid a circular list and skip interim queue merges */
         while ((__cfqq = new_cfqq->new_cfqq)) {
                 if (__cfqq == cfqq)
@@ -1994,17 +2003,17 @@ static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
         }
 
         process_refs = cfqq_process_refs(cfqq);
+        new_process_refs = cfqq_process_refs(new_cfqq);
         /*
          * If the process for the cfqq has gone away, there is no
          * sense in merging the queues.
          */
-        if (process_refs == 0)
+        if (process_refs == 0 || new_process_refs == 0)
                 return;
 
         /*
          * Merge in the direction of the lesser amount of work.
          */
-        new_process_refs = cfqq_process_refs(new_cfqq);
         if (new_process_refs >= process_refs) {
                 cfqq->new_cfqq = new_cfqq;
                 atomic_add(process_refs, &new_cfqq->ref);
@@ -3248,7 +3257,7 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                                 cfq_clear_cfqq_wait_request(cfqq);
                                 __blk_run_queue(cfqd->queue);
                         } else {
-                                blkiocg_update_idle_time_stats(
+                                cfq_blkiocg_update_idle_time_stats(
                                                 &cfqq->cfqg->blkg);
                                 cfq_mark_cfqq_must_dispatch(cfqq);
                         }
@@ -3276,7 +3285,7 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
         rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
         list_add_tail(&rq->queuelist, &cfqq->fifo);
         cfq_add_rq_rb(rq);
-        blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
+        cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
                         &cfqd->serving_group->blkg, rq_data_dir(rq),
                         rq_is_sync(rq));
         cfq_rq_enqueued(cfqd, cfqq, rq);
@@ -3364,9 +3373,9 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
         WARN_ON(!cfqq->dispatched);
         cfqd->rq_in_driver--;
         cfqq->dispatched--;
-        blkiocg_update_completion_stats(&cfqq->cfqg->blkg, rq_start_time_ns(rq),
-                        rq_io_start_time_ns(rq), rq_data_dir(rq),
-                        rq_is_sync(rq));
+        cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg,
+                        rq_start_time_ns(rq), rq_io_start_time_ns(rq),
+                        rq_data_dir(rq), rq_is_sync(rq));
 
         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
 
@@ -3730,7 +3739,7 @@ static void cfq_exit_queue(struct elevator_queue *e)
 
         cfq_put_async_queues(cfqd);
         cfq_release_cfq_groups(cfqd);
-        blkiocg_del_blkio_group(&cfqd->root_group.blkg);
+        cfq_blkiocg_del_blkio_group(&cfqd->root_group.blkg);
 
         spin_unlock_irq(q->queue_lock);
 
@@ -3798,8 +3807,8 @@ static void *cfq_init_queue(struct request_queue *q)
          */
         atomic_set(&cfqg->ref, 1);
         rcu_read_lock();
-        blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
-                                        0);
+        cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
+                                        (void *)cfqd, 0);
         rcu_read_unlock();
 #endif
         /*
diff --git a/block/cfq.h b/block/cfq.h
new file mode 100644
index 000000000000..93448e5a2e41
--- /dev/null
+++ b/block/cfq.h
@@ -0,0 +1,115 @@
+#ifndef _CFQ_H
+#define _CFQ_H
+#include "blk-cgroup.h"
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+static inline void cfq_blkiocg_update_io_add_stats(struct blkio_group *blkg,
+        struct blkio_group *curr_blkg, bool direction, bool sync)
+{
+        blkiocg_update_io_add_stats(blkg, curr_blkg, direction, sync);
+}
+
+static inline void cfq_blkiocg_update_dequeue_stats(struct blkio_group *blkg,
+                        unsigned long dequeue)
+{
+        blkiocg_update_dequeue_stats(blkg, dequeue);
+}
+
+static inline void cfq_blkiocg_update_timeslice_used(struct blkio_group *blkg,
+                        unsigned long time)
+{
+        blkiocg_update_timeslice_used(blkg, time);
+}
+
+static inline void cfq_blkiocg_set_start_empty_time(struct blkio_group *blkg)
+{
+        blkiocg_set_start_empty_time(blkg);
+}
+
+static inline void cfq_blkiocg_update_io_remove_stats(struct blkio_group *blkg,
+                                bool direction, bool sync)
+{
+        blkiocg_update_io_remove_stats(blkg, direction, sync);
+}
+
+static inline void cfq_blkiocg_update_io_merged_stats(struct blkio_group *blkg,
+                bool direction, bool sync)
+{
+        blkiocg_update_io_merged_stats(blkg, direction, sync);
+}
+
+static inline void cfq_blkiocg_update_idle_time_stats(struct blkio_group *blkg)
+{
+        blkiocg_update_idle_time_stats(blkg);
+}
+
+static inline void
+cfq_blkiocg_update_avg_queue_size_stats(struct blkio_group *blkg)
+{
+        blkiocg_update_avg_queue_size_stats(blkg);
+}
+
+static inline void
+cfq_blkiocg_update_set_idle_time_stats(struct blkio_group *blkg)
+{
+        blkiocg_update_set_idle_time_stats(blkg);
+}
+
+static inline void cfq_blkiocg_update_dispatch_stats(struct blkio_group *blkg,
+                                uint64_t bytes, bool direction, bool sync)
+{
+        blkiocg_update_dispatch_stats(blkg, bytes, direction, sync);
+}
+
+static inline void cfq_blkiocg_update_completion_stats(struct blkio_group *blkg, uint64_t start_time, uint64_t io_start_time, bool direction, bool sync)
+{
+        blkiocg_update_completion_stats(blkg, start_time, io_start_time,
+                                direction, sync);
+}
+
+static inline void cfq_blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
+                        struct blkio_group *blkg, void *key, dev_t dev) {
+        blkiocg_add_blkio_group(blkcg, blkg, key, dev);
+}
+
+static inline int cfq_blkiocg_del_blkio_group(struct blkio_group *blkg)
+{
+        return blkiocg_del_blkio_group(blkg);
+}
+
+#else /* CFQ_GROUP_IOSCHED */
+static inline void cfq_blkiocg_update_io_add_stats(struct blkio_group *blkg,
+        struct blkio_group *curr_blkg, bool direction, bool sync) {}
+
+static inline void cfq_blkiocg_update_dequeue_stats(struct blkio_group *blkg,
+                        unsigned long dequeue) {}
+
+static inline void cfq_blkiocg_update_timeslice_used(struct blkio_group *blkg,
+                        unsigned long time) {}
+static inline void cfq_blkiocg_set_start_empty_time(struct blkio_group *blkg) {}
+static inline void cfq_blkiocg_update_io_remove_stats(struct blkio_group *blkg,
+                                bool direction, bool sync) {}
+static inline void cfq_blkiocg_update_io_merged_stats(struct blkio_group *blkg,
+                bool direction, bool sync) {}
+static inline void cfq_blkiocg_update_idle_time_stats(struct blkio_group *blkg)
+{
+}
+static inline void
+cfq_blkiocg_update_avg_queue_size_stats(struct blkio_group *blkg) {}
+
+static inline void
+cfq_blkiocg_update_set_idle_time_stats(struct blkio_group *blkg) {}
+
+static inline void cfq_blkiocg_update_dispatch_stats(struct blkio_group *blkg,
+                                uint64_t bytes, bool direction, bool sync) {}
+static inline void cfq_blkiocg_update_completion_stats(struct blkio_group *blkg, uint64_t start_time, uint64_t io_start_time, bool direction, bool sync) {}
+
+static inline void cfq_blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
+                        struct blkio_group *blkg, void *key, dev_t dev) {}
+static inline int cfq_blkiocg_del_blkio_group(struct blkio_group *blkg)
+{
+        return 0;
+}
+
+#endif /* CFQ_GROUP_IOSCHED */
+#endif
diff --git a/drivers/block/cciss_scsi.c b/drivers/block/cciss_scsi.c
index 3381505c8a6c..72dae92f3cab 100644
--- a/drivers/block/cciss_scsi.c
+++ b/drivers/block/cciss_scsi.c
@@ -861,6 +861,7 @@ cciss_scsi_detect(int ctlr)
         sh->n_io_port = 0;      // I don't think we use these two...
         sh->this_id = SELF_SCSI_ID;  
         sh->sg_tablesize = hba[ctlr]->maxsgentries;
+        sh->max_cmd_len = MAX_COMMAND_SIZE;
 
         ((struct cciss_scsi_adapter_data_t *) 
                 hba[ctlr]->scsi_ctlr)->scsi_host = sh;
diff --git a/drivers/block/cpqarray.c b/drivers/block/cpqarray.c
index 91d11631cec9..abb4ec6690fc 100644
--- a/drivers/block/cpqarray.c
+++ b/drivers/block/cpqarray.c
@@ -386,7 +386,7 @@ static void __devexit cpqarray_remove_one_eisa (int i)
 }
 
 /* pdev is NULL for eisa */
-static int __init cpqarray_register_ctlr( int i, struct pci_dev *pdev)
+static int __devinit cpqarray_register_ctlr( int i, struct pci_dev *pdev)
 {
         struct request_queue *q;
         int j;
@@ -503,7 +503,7 @@ Enomem4:
         return -1;
 }
 
-static int __init cpqarray_init_one( struct pci_dev *pdev,
+static int __devinit cpqarray_init_one( struct pci_dev *pdev,
         const struct pci_device_id *ent)
 {
         int i;
@@ -740,7 +740,7 @@ __setup("smart2=", cpqarray_setup);
 /*
  * Find an EISA controller's signature.  Set up an hba if we find it.
  */
-static int __init cpqarray_eisa_detect(void)
+static int __devinit cpqarray_eisa_detect(void)
 {
         int i=0, j;
         __u32 board_id;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 6b077f93acc6..7258c95e895e 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1236,8 +1236,6 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
         /* Last part of the attaching process ... */
         if (ns.conn >= C_CONNECTED &&
             os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
-                kfree(mdev->p_uuid); /* We expect to receive up-to-date UUIDs soon. */
-                mdev->p_uuid = NULL; /* ...to not use the old ones in the mean time */
                 drbd_send_sizes(mdev, 0, 0);  /* to start sync... */
                 drbd_send_uuids(mdev);
                 drbd_send_state(mdev);
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 632e3245d1bb..2151f18b21de 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1114,6 +1114,12 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
                 mdev->new_state_tmp.i = ns.i;
                 ns.i = os.i;
                 ns.disk = D_NEGOTIATING;
+
+                /* We expect to receive up-to-date UUIDs soon.
+                   To avoid a race in receive_state, free p_uuid while
+                   holding req_lock. I.e. atomic with the state change */
+                kfree(mdev->p_uuid);
+                mdev->p_uuid = NULL;
         }
 
         rv = _drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1d1088f48bc2..0609607d3955 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -63,24 +63,16 @@ struct bdi_work {
 };
 
 enum {
-        WS_USED_B = 0,
-        WS_ONSTACK_B,
+        WS_INPROGRESS = 0,
+        WS_ONSTACK,
 };
 
-#define WS_USED (1 << WS_USED_B)
-#define WS_ONSTACK (1 << WS_ONSTACK_B)
-
-static inline bool bdi_work_on_stack(struct bdi_work *work)
-{
-        return test_bit(WS_ONSTACK_B, &work->state);
-}
-
 static inline void bdi_work_init(struct bdi_work *work,
                                  struct wb_writeback_args *args)
 {
         INIT_RCU_HEAD(&work->rcu_head);
         work->args = *args;
-        work->state = WS_USED;
+        __set_bit(WS_INPROGRESS, &work->state);
 }
 
 /**
@@ -95,43 +87,16 @@ int writeback_in_progress(struct backing_dev_info *bdi)
         return !list_empty(&bdi->work_list);
 }
 
-static void bdi_work_clear(struct bdi_work *work)
-{
-        clear_bit(WS_USED_B, &work->state);
-        smp_mb__after_clear_bit();
-        /*
-         * work can have disappeared at this point. bit waitq functions
-         * should be able to tolerate this, provided bdi_sched_wait does
-         * not dereference it's pointer argument.
-        */
-        wake_up_bit(&work->state, WS_USED_B);
-}
-
 static void bdi_work_free(struct rcu_head *head)
 {
         struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
 
-        if (!bdi_work_on_stack(work))
-                kfree(work);
-        else
-                bdi_work_clear(work);
-}
-
-static void wb_work_complete(struct bdi_work *work)
-{
-        const enum writeback_sync_modes sync_mode = work->args.sync_mode;
-        int onstack = bdi_work_on_stack(work);
+        clear_bit(WS_INPROGRESS, &work->state);
+        smp_mb__after_clear_bit();
+        wake_up_bit(&work->state, WS_INPROGRESS);
 
-        /*
-         * For allocated work, we can clear the done/seen bit right here.
-         * For on-stack work, we need to postpone both the clear and free
-         * to after the RCU grace period, since the stack could be invalidated
-         * as soon as bdi_work_clear() has done the wakeup.
-         */
-        if (!onstack)
-                bdi_work_clear(work);
-        if (sync_mode == WB_SYNC_NONE || onstack)
-                call_rcu(&work->rcu_head, bdi_work_free);
+        if (!test_bit(WS_ONSTACK, &work->state))
+                kfree(work);
 }
 
 static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
@@ -147,7 +112,7 @@ static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
                 list_del_rcu(&work->list);
                 spin_unlock(&bdi->wb_lock);
 
-                wb_work_complete(work);
+                call_rcu(&work->rcu_head, bdi_work_free);
         }
 }
 
@@ -185,9 +150,9 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
  * Used for on-stack allocated work items. The caller needs to wait until
  * the wb threads have acked the work before it's safe to continue.
  */
-static void bdi_wait_on_work_clear(struct bdi_work *work)
+static void bdi_wait_on_work_done(struct bdi_work *work)
 {
-        wait_on_bit(&work->state, WS_USED_B, bdi_sched_wait,
+        wait_on_bit(&work->state, WS_INPROGRESS, bdi_sched_wait,
                     TASK_UNINTERRUPTIBLE);
 }
 
@@ -213,37 +178,28 @@ static void bdi_alloc_queue_work(struct backing_dev_info *bdi,
 }
 
 /**
- * bdi_sync_writeback - start and wait for writeback
- * @bdi: the backing device to write from
+ * bdi_queue_work_onstack - start and wait for writeback
  * @sb: write inodes from this super_block
  *
  * Description:
- *   This does WB_SYNC_ALL data integrity writeback and waits for the
- *   IO to complete. Callers must hold the sb s_umount semaphore for
+ *   This function initiates writeback and waits for the operation to
+ *   complete. Callers must hold the sb s_umount semaphore for
  *   reading, to avoid having the super disappear before we are done.
  */
-static void bdi_sync_writeback(struct backing_dev_info *bdi,
-                               struct super_block *sb)
+static void bdi_queue_work_onstack(struct wb_writeback_args *args)
 {
-        struct wb_writeback_args args = {
-                .sb             = sb,
-                .sync_mode      = WB_SYNC_ALL,
-                .nr_pages       = LONG_MAX,
-                .range_cyclic   = 0,
-        };
         struct bdi_work work;
 
-        bdi_work_init(&work, &args);
-        work.state |= WS_ONSTACK;
+        bdi_work_init(&work, args);
+        __set_bit(WS_ONSTACK, &work.state);
 
-        bdi_queue_work(bdi, &work);
-        bdi_wait_on_work_clear(&work);
+        bdi_queue_work(args->sb->s_bdi, &work);
+        bdi_wait_on_work_done(&work);
 }
 
 /**
  * bdi_start_writeback - start writeback
  * @bdi: the backing device to write from
- * @sb: write inodes from this super_block
  * @nr_pages: the number of pages to write
  *
  * Description:
@@ -252,25 +208,34 @@ static void bdi_sync_writeback(struct backing_dev_info *bdi,
  *   completion. Caller need not hold sb s_umount semaphore.
  *
  */
-void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
-                         long nr_pages)
+void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
 {
         struct wb_writeback_args args = {
-                .sb             = sb,
                 .sync_mode      = WB_SYNC_NONE,
                 .nr_pages       = nr_pages,
                 .range_cyclic   = 1,
         };
 
-        /*
-         * We treat @nr_pages=0 as the special case to do background writeback,
-         * ie. to sync pages until the background dirty threshold is reached.
-         */
-        if (!nr_pages) {
-                args.nr_pages = LONG_MAX;
-                args.for_background = 1;
-        }
+        bdi_alloc_queue_work(bdi, &args);
+}
 
+/**
+ * bdi_start_background_writeback - start background writeback
+ * @bdi: the backing device to write from
+ *
+ * Description:
+ *   This does WB_SYNC_NONE background writeback. The IO is only
+ *   started when this function returns, we make no guarentees on
+ *   completion. Caller need not hold sb s_umount semaphore.
+ */
+void bdi_start_background_writeback(struct backing_dev_info *bdi)
+{
+        struct wb_writeback_args args = {
+                .sync_mode      = WB_SYNC_NONE,
+                .nr_pages       = LONG_MAX,
+                .for_background = 1,
+                .range_cyclic   = 1,
+        };
         bdi_alloc_queue_work(bdi, &args);
 }
 
@@ -561,48 +526,30 @@ select_queue:
         return ret;
 }
 
-static void unpin_sb_for_writeback(struct super_block *sb)
-{
-        up_read(&sb->s_umount);
-        put_super(sb);
-}
-
-enum sb_pin_state {
-        SB_PINNED,
-        SB_NOT_PINNED,
-        SB_PIN_FAILED
-};
-
 /*
- * For WB_SYNC_NONE writeback, the caller does not have the sb pinned
+ * For background writeback the caller does not have the sb pinned
  * before calling writeback. So make sure that we do pin it, so it doesn't
  * go away while we are writing inodes from it.
  */
-static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
-                                              struct super_block *sb)
+static bool pin_sb_for_writeback(struct super_block *sb)
 {
-        /*
-         * Caller must already hold the ref for this
-         */
-        if (wbc->sync_mode == WB_SYNC_ALL) {
-                WARN_ON(!rwsem_is_locked(&sb->s_umount));
-                return SB_NOT_PINNED;
-        }
         spin_lock(&sb_lock);
+        if (list_empty(&sb->s_instances)) {
+                spin_unlock(&sb_lock);
+                return false;
+        }
+
         sb->s_count++;
+        spin_unlock(&sb_lock);
+
         if (down_read_trylock(&sb->s_umount)) {
-                if (sb->s_root) {
-                        spin_unlock(&sb_lock);
-                        return SB_PINNED;
-                }
-                /*
-                 * umounted, drop rwsem again and fall through to failure
-                 */
+                if (sb->s_root)
+                        return true;
                 up_read(&sb->s_umount);
         }
-        sb->s_count--;
-        spin_unlock(&sb_lock);
-        return SB_PIN_FAILED;
+
+        put_super(sb);
+        return false;
 }
 
 /*
@@ -681,24 +628,31 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
                 struct inode *inode = list_entry(wb->b_io.prev,
                                                  struct inode, i_list);
                 struct super_block *sb = inode->i_sb;
-                enum sb_pin_state state;
 
-                if (wbc->sb && sb != wbc->sb) {
-                        /* super block given and doesn't
-                           match, skip this inode */
-                        redirty_tail(inode);
-                        continue;
-                }
-                state = pin_sb_for_writeback(wbc, sb);
+                if (wbc->sb) {
+                        /*
+                         * We are requested to write out inodes for a specific
+                         * superblock.  This means we already have s_umount
+                         * taken by the caller which also waits for us to
+                         * complete the writeout.
+                         */
+                        if (sb != wbc->sb) {
+                                redirty_tail(inode);
+                                continue;
+                        }
 
-                if (state == SB_PIN_FAILED) {
-                        requeue_io(inode);
-                        continue;
+                        WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
+                        ret = writeback_sb_inodes(sb, wb, wbc);
+                } else {
+                        if (!pin_sb_for_writeback(sb)) {
+                                requeue_io(inode);
+                                continue;
+                        }
+                        ret = writeback_sb_inodes(sb, wb, wbc);
+                        drop_super(sb);
                 }
-                ret = writeback_sb_inodes(sb, wb, wbc);
 
-                if (state == SB_PINNED)
-                        unpin_sb_for_writeback(sb);
                 if (ret)
                         break;
         }
@@ -911,7 +865,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
                  * If this isn't a data integrity operation, just notify
                  * that we have seen this work and we are now starting it.
                  */
-                if (args.sync_mode == WB_SYNC_NONE)
+                if (!test_bit(WS_ONSTACK, &work->state))
                         wb_clear_pending(wb, work);
 
                 wrote += wb_writeback(wb, &args);
@@ -920,7 +874,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
                  * This is a data integrity writeback, so only do the
                  * notification when we have completed the work.
                  */
-                if (args.sync_mode == WB_SYNC_ALL)
+                if (test_bit(WS_ONSTACK, &work->state))
                         wb_clear_pending(wb, work);
         }
 
@@ -978,42 +932,32 @@ int bdi_writeback_task(struct bdi_writeback *wb)
 }
 
 /*
- * Schedule writeback for all backing devices. This does WB_SYNC_NONE
- * writeback, for integrity writeback see bdi_sync_writeback().
+ * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
+ * the whole world.
  */
-static void bdi_writeback_all(struct super_block *sb, long nr_pages)
+void wakeup_flusher_threads(long nr_pages)
 {
+        struct backing_dev_info *bdi;
         struct wb_writeback_args args = {
-                .sb             = sb,
-                .nr_pages       = nr_pages,
                 .sync_mode      = WB_SYNC_NONE,
         };
-        struct backing_dev_info *bdi;
 
-        rcu_read_lock();
+        if (nr_pages) {
+                args.nr_pages = nr_pages;
+        } else {
+                args.nr_pages = global_page_state(NR_FILE_DIRTY) +
+                                global_page_state(NR_UNSTABLE_NFS);
+        }
 
+        rcu_read_lock();
         list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
                 if (!bdi_has_dirty_io(bdi))
                         continue;
-
                 bdi_alloc_queue_work(bdi, &args);
         }
-
         rcu_read_unlock();
 }
 
-/*
- * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
- * the whole world.
- */
-void wakeup_flusher_threads(long nr_pages)
-{
-        if (nr_pages == 0)
-                nr_pages = global_page_state(NR_FILE_DIRTY) +
-                                global_page_state(NR_UNSTABLE_NFS);
-        bdi_writeback_all(NULL, nr_pages);
-}
-
 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
 {
         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
@@ -1218,12 +1162,17 @@ void writeback_inodes_sb(struct super_block *sb)
 {
         unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
         unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
-        long nr_to_write;
+        struct wb_writeback_args args = {
+                .sb             = sb,
+                .sync_mode      = WB_SYNC_NONE,
+        };
+
+        WARN_ON(!rwsem_is_locked(&sb->s_umount));
 
-        nr_to_write = nr_dirty + nr_unstable +
+        args.nr_pages = nr_dirty + nr_unstable +
                         (inodes_stat.nr_inodes - inodes_stat.nr_unused);
 
-        bdi_start_writeback(sb->s_bdi, sb, nr_to_write);
+        bdi_queue_work_onstack(&args);
 }
 EXPORT_SYMBOL(writeback_inodes_sb);
 
@@ -1237,7 +1186,9 @@ EXPORT_SYMBOL(writeback_inodes_sb);
 int writeback_inodes_sb_if_idle(struct super_block *sb)
 {
         if (!writeback_in_progress(sb->s_bdi)) {
+                down_read(&sb->s_umount);
                 writeback_inodes_sb(sb);
+                up_read(&sb->s_umount);
                 return 1;
         } else
                 return 0;
@@ -1253,7 +1204,16 @@ EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
  */
 void sync_inodes_sb(struct super_block *sb)
 {
-        bdi_sync_writeback(sb->s_bdi, sb);
+        struct wb_writeback_args args = {
+                .sb             = sb,
+                .sync_mode      = WB_SYNC_ALL,
+                .nr_pages       = LONG_MAX,
+                .range_cyclic   = 0,
+        };
+
+        WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
+        bdi_queue_work_onstack(&args);
         wait_sb_inodes(sb);
 }
 EXPORT_SYMBOL(sync_inodes_sb);
diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
index 076ca50e9933..c8ff0d1ae5d3 100644
--- a/fs/ubifs/budget.c
+++ b/fs/ubifs/budget.c
@@ -62,7 +62,9 @@
  */
 static void shrink_liability(struct ubifs_info *c, int nr_to_write)
 {
+        down_read(&c->vfs_sb->s_umount);
         writeback_inodes_sb(c->vfs_sb);
+        up_read(&c->vfs_sb->s_umount);
 }
 
 /**
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index aee5f6ce166e..9ae2889096b6 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -105,8 +105,8 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
 void bdi_unregister(struct backing_dev_info *bdi);
 int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int);
-void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
-                                long nr_pages);
+void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages);
+void bdi_start_background_writeback(struct backing_dev_info *bdi);
 int bdi_writeback_task(struct bdi_writeback *wb);
 int bdi_has_dirty_io(struct backing_dev_info *bdi);
 void bdi_arm_supers_timer(void);
diff --git a/include/linux/drbd.h b/include/linux/drbd.h
index 30da4ae48972..b8d2516668aa 100644
--- a/include/linux/drbd.h
+++ b/include/linux/drbd.h
@@ -53,7 +53,7 @@
 
 
 extern const char *drbd_buildtag(void);
-#define REL_VERSION "8.3.8rc2"
+#define REL_VERSION "8.3.8"
 #define API_VERSION 88
 #define PRO_VERSION_MIN 86
 #define PRO_VERSION_MAX 94
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index bbd396ac9546..54f28bd493d3 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -597,7 +597,7 @@ static void balance_dirty_pages(struct address_space *mapping,
             (!laptop_mode && ((global_page_state(NR_FILE_DIRTY)
                                + global_page_state(NR_UNSTABLE_NFS))
                                           > background_thresh)))
-                bdi_start_writeback(bdi, NULL, 0);
+                bdi_start_background_writeback(bdi);
 }
 
 void set_page_dirty_balance(struct page *page, int page_mkwrite)
@@ -705,9 +705,8 @@ void laptop_mode_timer_fn(unsigned long data)
          * We want to write everything out, not just down to the dirty
          * threshold
          */
-
         if (bdi_has_dirty_io(&q->backing_dev_info))
-                bdi_start_writeback(&q->backing_dev_info, NULL, nr_pages);
+                bdi_start_writeback(&q->backing_dev_info, nr_pages);
 }
 
 /*