Do not allow more than one merging snapshot. It is pointless to merge two snapshots simultaneously. Allowing multiple merging snapshots would complicate things later. Adds function to find merging snapshot for a given origin device. Signed-off-by: Mikulas Patocka Reviewed-by: Mike Snitzer --- drivers/md/dm-snap.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) Index: linux-2.6.31-fast-new-2/drivers/md/dm-snap.c =================================================================== --- linux-2.6.31-fast-new-2.orig/drivers/md/dm-snap.c 2009-10-16 21:48:28.000000000 +0200 +++ linux-2.6.31-fast-new-2/drivers/md/dm-snap.c 2009-10-16 21:48:31.000000000 +0200 @@ -305,6 +305,22 @@ static void __insert_origin(struct origi list_add_tail(&o->hash_list, sl); } +static struct dm_snapshot *__find_merging_snapshot(struct block_device *origin) +{ + struct origin *o; + struct dm_snapshot *snap; + + o = __lookup_origin(origin); + if (!o) + return NULL; + + list_for_each_entry(snap, &o->snapshots, list) + if (is_merge(snap->ti)) + return snap; + + return NULL; +} + /* * Make a note of the snapshot and its origin so we can look it * up when the origin has a write on it. @@ -320,6 +336,13 @@ static int register_snapshot(struct dm_s return -ENOMEM; down_write(&_origins_lock); + + /* Do not allow more than one merging snapshot */ + if (is_merge(snap->ti) && __find_merging_snapshot(bdev)) { + up_write(&_origins_lock); + return -EINVAL; + } + o = __lookup_origin(bdev); if (o)