dm: merge pushback and deferred bio lists

Merge pushback and deferred lists into one list - use deferred list
for both deferred and pushed-back bios.

This will be needed for proper support of barrier bios: it is impossible to
support ordering correctly with two lists because the requests on both lists
will be mixed up.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 16 insertions, 21 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ae21833b270a..f5703727d974 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -102,7 +102,6 @@ union map_info *dm_get_mapinfo(struct bio *bio)
 struct mapped_device {
         struct rw_semaphore io_lock;
         struct mutex suspend_lock;
-        spinlock_t pushback_lock;
         rwlock_t map_lock;
         atomic_t holders;
         atomic_t open_count;
@@ -122,7 +121,7 @@ struct mapped_device {
         wait_queue_head_t wait;
         struct work_struct work;
         struct bio_list deferred;
-        struct bio_list pushback;
+        spinlock_t deferred_lock;
 
         /*
          * Processing queue (flush/barriers)
@@ -445,7 +444,9 @@ static int queue_io(struct mapped_device *md, struct bio *bio)
                 return 1;
         }
 
+        spin_lock_irq(&md->deferred_lock);
         bio_list_add(&md->deferred, bio);
+        spin_unlock_irq(&md->deferred_lock);
 
         up_write(&md->io_lock);
         return 0;               /* deferred successfully */
@@ -529,16 +530,14 @@ static void dec_pending(struct dm_io *io, int error)
                 if (io->error == DM_ENDIO_REQUEUE) {
                         /*
                          * Target requested pushing back the I/O.
-                         * This must be handled before the sleeper on
-                         * suspend queue merges the pushback list.
                          */
-                        spin_lock_irqsave(&md->pushback_lock, flags);
+                        spin_lock_irqsave(&md->deferred_lock, flags);
                         if (__noflush_suspending(md))
-                                bio_list_add(&md->pushback, io->bio);
+                                bio_list_add(&md->deferred, io->bio);
                         else
                                 /* noflush suspend was interrupted. */
                                 io->error = -EIO;
-                        spin_unlock_irqrestore(&md->pushback_lock, flags);
+                        spin_unlock_irqrestore(&md->deferred_lock, flags);
                 }
 
                 end_io_acct(io);
@@ -1096,7 +1095,7 @@ static struct mapped_device *alloc_dev(int minor)
 
         init_rwsem(&md->io_lock);
         mutex_init(&md->suspend_lock);
-        spin_lock_init(&md->pushback_lock);
+        spin_lock_init(&md->deferred_lock);
         rwlock_init(&md->map_lock);
         atomic_set(&md->holders, 1);
         atomic_set(&md->open_count, 0);
@@ -1410,25 +1409,21 @@ static void dm_wq_work(struct work_struct *work)
 
         down_write(&md->io_lock);
 
-        while ((c = bio_list_pop(&md->deferred)))
+next_bio:
+        spin_lock_irq(&md->deferred_lock);
+        c = bio_list_pop(&md->deferred);
+        spin_unlock_irq(&md->deferred_lock);
+
+        if (c) {
                 __split_and_process_bio(md, c);
+                goto next_bio;
+        }
 
         clear_bit(DMF_BLOCK_IO, &md->flags);
 
         up_write(&md->io_lock);
 }
 
-static void __merge_pushback_list(struct mapped_device *md)
-{
-        unsigned long flags;
-
-        spin_lock_irqsave(&md->pushback_lock, flags);
-        clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
-        bio_list_merge_head(&md->deferred, &md->pushback);
-        bio_list_init(&md->pushback);
-        spin_unlock_irqrestore(&md->pushback_lock, flags);
-}
-
 static void dm_queue_flush(struct mapped_device *md)
 {
         queue_work(md->wq, &md->work);
@@ -1572,7 +1567,7 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
         remove_wait_queue(&md->wait, &wait);
 
         if (noflush)
-                __merge_pushback_list(md);
+                clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
         up_write(&md->io_lock);
 
         /* were we interrupted ? */