Commit 4c6fff44 authored Oct 16, 2009 by Mikulas Patocka Committed by Alasdair G Kergon Oct 16, 2009

dm snapshot: lock snapshot while supplying status



This patch locks the snapshot when returning status.  It fixes a race
when it could return an invalid number of free chunks if someone
was simultaneously modifying it.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

parent 0e8c4e4e

drivers/md/dm-snap.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1152,6 +1152,8 @@ 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:
		if (!snap->valid)
		@@ -1183,6 +1185,8 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
		break;
		}

		up_write(&snap->lock);

		return 0;
		}