diff options
| author | Junxiao Bi | 2019-07-09 17:17:19 -0700 |
|---|---|---|
| committer | Mike Snitzer | 2019-07-12 09:59:37 -0400 |
| commit | bd293d071ffe65e645b4d8104f9d8fe15ea13862 (patch) | |
| tree | 29faa2ee05ac191581222287a36886738e33ef00 /drivers/md | |
| parent | 2e6023850e177dbaca21498ada04c5a5ac93f812 (diff) | |
dm bufio: fix deadlock with loop device
When thin-volume is built on loop device, if available memory is low,
the following deadlock can be triggered:
One process P1 allocates memory with GFP_FS flag, direct alloc fails,
memory reclaim invokes memory shrinker in dm_bufio, dm_bufio_shrink_scan()
runs, mutex dm_bufio_client->lock is acquired, then P1 waits for dm_buffer
IO to complete in __try_evict_buffer().
But this IO may never complete if issued to an underlying loop device
that forwards it using direct-IO, which allocates memory using
GFP_KERNEL (see: do_blockdev_direct_IO()). If allocation fails, memory
reclaim will invoke memory shrinker in dm_bufio, dm_bufio_shrink_scan()
will be invoked, and since the mutex is already held by P1 the loop
thread will hang, and IO will never complete. Resulting in ABBA
deadlock.
Cc: stable@vger.kernel.org
Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm-bufio.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index 2a48ea3f1b30..b6b5acc92ca2 100644 --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -1599,9 +1599,7 @@ dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) unsigned long freed; c = container_of(shrink, struct dm_bufio_client, shrinker); - if (sc->gfp_mask & __GFP_FS) - dm_bufio_lock(c); - else if (!dm_bufio_trylock(c)) + if (!dm_bufio_trylock(c)) return SHRINK_STOP; freed = __scan(c, sc->nr_to_scan, sc->gfp_mask); |