dm crypt: wait for endio to complete before destruction

The following oops has been reported when dm-crypt runs over a loop device.

...
[   70.381058] Process loop0 (pid: 4268, ti=cf3b2000 task=cf1cc1f0 task.ti=cf3b2000)
...
[   70.381058] Call Trace:
[   70.381058]  [<d0d76601>] ? crypt_dec_pending+0x5e/0x62 [dm_crypt]
[   70.381058]  [<d0d767b8>] ? crypt_endio+0xa2/0xaa [dm_crypt]
[   70.381058]  [<d0d76716>] ? crypt_endio+0x0/0xaa [dm_crypt]
[   70.381058]  [<c01a2f24>] ? bio_endio+0x2b/0x2e
[   70.381058]  [<d0806530>] ? dec_pending+0x224/0x23b [dm_mod]
[   70.381058]  [<d08066e4>] ? clone_endio+0x79/0xa4 [dm_mod]
[   70.381058]  [<d080666b>] ? clone_endio+0x0/0xa4 [dm_mod]
[   70.381058]  [<c01a2f24>] ? bio_endio+0x2b/0x2e
[   70.381058]  [<c02bad86>] ? loop_thread+0x380/0x3b7
[   70.381058]  [<c02ba8a1>] ? do_lo_send_aops+0x0/0x165
[   70.381058]  [<c013754f>] ? autoremove_wake_function+0x0/0x33
[   70.381058]  [<c02baa06>] ? loop_thread+0x0/0x3b7

When a table is being replaced, it waits for I/O to complete
before destroying the mempool, but the endio function doesn't
call mempool_free() until after completing the bio.

Fix it by swapping the order of those two operations.

The same problem occurs in dm.c with md referenced after dec_pending.
Again, we swap the order.

Cc: stable@kernel.org
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

2 files changed, 29 insertions, 20 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index ebab49f8cc1d..bfefd079a955 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -568,19 +568,22 @@ static void crypt_inc_pending(struct dm_crypt_io *io)
 static void crypt_dec_pending(struct dm_crypt_io *io)
 {
         struct crypt_config *cc = io->target->private;
+        struct bio *base_bio = io->base_bio;
+        struct dm_crypt_io *base_io = io->base_io;
+        int error = io->error;
 
         if (!atomic_dec_and_test(&io->pending))
                 return;
 
-        if (likely(!io->base_io))
-                bio_endio(io->base_bio, io->error);
+        mempool_free(io, cc->io_pool);
+
+        if (likely(!base_io))
+                bio_endio(base_bio, error);
         else {
-                if (io->error && !io->base_io->error)
-                        io->base_io->error = io->error;
-                crypt_dec_pending(io->base_io);
+                if (error && !base_io->error)
+                        base_io->error = error;
+                crypt_dec_pending(base_io);
         }
-
-        mempool_free(io, cc->io_pool);
 }
 
 /*
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 51ba1db4b3e7..8d40f27cce89 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -525,9 +525,12 @@ static int __noflush_suspending(struct mapped_device *md)
 static void dec_pending(struct dm_io *io, int error)
 {
         unsigned long flags;
+        int io_error;
+        struct bio *bio;
+        struct mapped_device *md = io->md;
 
         /* Push-back supersedes any I/O errors */
-        if (error && !(io->error > 0 && __noflush_suspending(io->md)))
+        if (error && !(io->error > 0 && __noflush_suspending(md)))
                 io->error = error;
 
         if (atomic_dec_and_test(&io->io_count)) {
@@ -537,24 +540,27 @@ static void dec_pending(struct dm_io *io, int error)
                          * This must be handled before the sleeper on
                          * suspend queue merges the pushback list.
                          */
-                        spin_lock_irqsave(&io->md->pushback_lock, flags);
-                        if (__noflush_suspending(io->md))
-                                bio_list_add(&io->md->pushback, io->bio);
+                        spin_lock_irqsave(&md->pushback_lock, flags);
+                        if (__noflush_suspending(md))
+                                bio_list_add(&md->pushback, io->bio);
                         else
                                 /* noflush suspend was interrupted. */
                                 io->error = -EIO;
-                        spin_unlock_irqrestore(&io->md->pushback_lock, flags);
+                        spin_unlock_irqrestore(&md->pushback_lock, flags);
                 }
 
                 end_io_acct(io);
 
-                if (io->error != DM_ENDIO_REQUEUE) {
-                        trace_block_bio_complete(io->md->queue, io->bio);
+                io_error = io->error;
+                bio = io->bio;
 
-                        bio_endio(io->bio, io->error);
-                }
+                free_io(md, io);
+
+                if (io_error != DM_ENDIO_REQUEUE) {
+                        trace_block_bio_complete(md->queue, bio);
 
-                free_io(io->md, io);
+                        bio_endio(bio, io_error);
+                }
         }
 }
 
@@ -562,6 +568,7 @@ static void clone_endio(struct bio *bio, int error)
 {
         int r = 0;
         struct dm_target_io *tio = bio->bi_private;
+        struct dm_io *io = tio->io;
         struct mapped_device *md = tio->io->md;
         dm_endio_fn endio = tio->ti->type->end_io;
 
@@ -585,15 +592,14 @@ static void clone_endio(struct bio *bio, int error)
                 }
         }
 
-        dec_pending(tio->io, error);
-
         /*
          * Store md for cleanup instead of tio which is about to get freed.
          */
         bio->bi_private = md->bs;
 
-        bio_put(bio);
         free_tio(md, tio);
+        bio_put(bio);
+        dec_pending(io, error);
 }
 
 static sector_t max_io_len(struct mapped_device *md,