1 files changed, 68 insertions, 20 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index db022e5f3912..8a994be035ba 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -125,6 +125,11 @@ struct mapped_device {
         spinlock_t deferred_lock;
 
         /*
+         * An error from the barrier request currently being processed.
+         */
+        int barrier_error;
+
+        /*
          * Processing queue (flush/barriers)
          */
         struct workqueue_struct *wq;
@@ -425,6 +430,10 @@ static void end_io_acct(struct dm_io *io)
         part_stat_add(cpu, &dm_disk(md)->part0, ticks[rw], duration);
         part_stat_unlock();
 
+        /*
+         * After this is decremented the bio must not be touched if it is
+         * a barrier.
+         */
         dm_disk(md)->part0.in_flight = pending =
                 atomic_dec_return(&md->pending);
 
@@ -531,25 +540,35 @@ static void dec_pending(struct dm_io *io, int error)
                          */
                         spin_lock_irqsave(&md->deferred_lock, flags);
                         if (__noflush_suspending(md))
-                                bio_list_add(&md->deferred, io->bio);
+                                bio_list_add_head(&md->deferred, io->bio);
                         else
                                 /* noflush suspend was interrupted. */
                                 io->error = -EIO;
                         spin_unlock_irqrestore(&md->deferred_lock, flags);
                 }
 
-                end_io_acct(io);
-
                 io_error = io->error;
                 bio = io->bio;
 
-                free_io(md, io);
+                if (bio_barrier(bio)) {
+                        /*
+                         * There can be just one barrier request so we use
+                         * a per-device variable for error reporting.
+                         * Note that you can't touch the bio after end_io_acct
+                         */
+                        md->barrier_error = io_error;
+                        end_io_acct(io);
+                } else {
+                        end_io_acct(io);
 
-                if (io_error != DM_ENDIO_REQUEUE) {
-                        trace_block_bio_complete(md->queue, bio);
+                        if (io_error != DM_ENDIO_REQUEUE) {
+                                trace_block_bio_complete(md->queue, bio);
 
-                        bio_endio(bio, io_error);
+                                bio_endio(bio, io_error);
+                        }
                 }
+
+                free_io(md, io);
         }
 }
 
@@ -691,7 +710,7 @@ static struct bio *split_bvec(struct bio *bio, sector_t sector,
 
         clone->bi_sector = sector;
         clone->bi_bdev = bio->bi_bdev;
-        clone->bi_rw = bio->bi_rw;
+        clone->bi_rw = bio->bi_rw & ~(1 << BIO_RW_BARRIER);
         clone->bi_vcnt = 1;
         clone->bi_size = to_bytes(len);
         clone->bi_io_vec->bv_offset = offset;
@@ -718,6 +737,7 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector,
 
         clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs);
         __bio_clone(clone, bio);
+        clone->bi_rw &= ~(1 << BIO_RW_BARRIER);
         clone->bi_destructor = dm_bio_destructor;
         clone->bi_sector = sector;
         clone->bi_idx = idx;
@@ -846,7 +866,10 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
 
         ci.map = dm_get_table(md);
         if (unlikely(!ci.map)) {
-                bio_io_error(bio);
+                if (!bio_barrier(bio))
+                        bio_io_error(bio);
+                else
+                        md->barrier_error = -EIO;
                 return;
         }
 
@@ -930,15 +953,6 @@ static int dm_request(struct request_queue *q, struct bio *bio)
         struct mapped_device *md = q->queuedata;
         int cpu;
 
-        /*
-         * There is no use in forwarding any barrier request since we can't
-         * guarantee it is (or can be) handled by the targets correctly.
-         */
-        if (unlikely(bio_barrier(bio))) {
-                bio_endio(bio, -EOPNOTSUPP);
-                return 0;
-        }
-
         down_read(&md->io_lock);
 
         cpu = part_stat_lock();
@@ -950,7 +964,8 @@ static int dm_request(struct request_queue *q, struct bio *bio)
          * If we're suspended or the thread is processing barriers
          * we have to queue this io for later.
          */
-        if (unlikely(test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags))) {
+        if (unlikely(test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) ||
+            unlikely(bio_barrier(bio))) {
                 up_read(&md->io_lock);
 
                 if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) &&
@@ -1415,6 +1430,36 @@ static int dm_wait_for_completion(struct mapped_device *md, int interruptible)
         return r;
 }
 
+static int dm_flush(struct mapped_device *md)
+{
+        dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);
+        return 0;
+}
+
+static void process_barrier(struct mapped_device *md, struct bio *bio)
+{
+        int error = dm_flush(md);
+
+        if (unlikely(error)) {
+                bio_endio(bio, error);
+                return;
+        }
+        if (bio_empty_barrier(bio)) {
+                bio_endio(bio, 0);
+                return;
+        }
+
+        __split_and_process_bio(md, bio);
+
+        error = dm_flush(md);
+
+        if (!error && md->barrier_error)
+                error = md->barrier_error;
+
+        if (md->barrier_error != DM_ENDIO_REQUEUE)
+                bio_endio(bio, error);
+}
+
 /*
  * Process the deferred bios
  */
@@ -1438,7 +1483,10 @@ static void dm_wq_work(struct work_struct *work)
 
                 up_write(&md->io_lock);
 
-                __split_and_process_bio(md, c);
+                if (bio_barrier(c))
+                        process_barrier(md, c);
+                else
+                        __split_and_process_bio(md, c);
 
                 down_write(&md->io_lock);
         }