From: Mikulas Patocka Take snapshot lock only for STATUSTYPE_INFO, not STATUSTYPE_TABLE. Commit 4c6fff445d7aa753957856278d4d93bcad6e2c14 (dm-snapshot-lock-snapshot-while-supplying-status.patch) introduced this use of the lock, but userspace applications using libdevmapper have been found to request STATUSTYPE_TABLE while the device is suspended and the lock is already held, leading to deadlock. Since the lock is not necessary in this case, don't try to take it. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- drivers/md/dm-snap.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) Index: linux-2.6.32/drivers/md/dm-snap.c =================================================================== --- linux-2.6.32.orig/drivers/md/dm-snap.c +++ linux-2.6.32/drivers/md/dm-snap.c @@ -1152,10 +1152,11 @@ static int snapshot_status(struct dm_tar unsigned sz = 0; struct dm_snapshot *snap = ti->private; - down_write(&snap->lock); - switch (type) { case STATUSTYPE_INFO: + + down_write(&snap->lock); + if (!snap->valid) DMEMIT("Invalid"); else { @@ -1171,6 +1172,9 @@ static int snapshot_status(struct dm_tar else DMEMIT("Unknown"); } + + up_write(&snap->lock); + break; case STATUSTYPE_TABLE: @@ -1185,8 +1189,6 @@ static int snapshot_status(struct dm_tar break; } - up_write(&snap->lock); - return 0; }