Commit 94e76572 authored Dec 10, 2009 by Mikulas Patocka Committed by Alasdair G Kergon Dec 10, 2009

dm snapshot: only take lock for statustype info not table



Take snapshot lock only for STATUSTYPE_INFO, not STATUSTYPE_TABLE.

Commit 4c6fff44
(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 <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

parent d2bb7df8

drivers/md/dm-snap.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -1152,10 +1152,11 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
		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_target *ti, status_type_t type,
		else
		DMEMIT("Unknown");
		}

		up_write(&snap->lock);

		break;

		case STATUSTYPE_TABLE:
		@@ -1185,8 +1189,6 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
		break;
		}

		up_write(&snap->lock);

		return 0;
		}