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>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index ebab49f..bfefd07 100644 (file)
--- 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 51ba1db..8d40f27 100644 (file)
--- 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,