From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
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 <mpatocka@xxxxxxxxxx>
Reviewed-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-snap.c | 23 +++++++++++++++++++++++
1 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index ea3ff81..c422355 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -305,6 +305,22 @@ static void __insert_origin(struct origin *o)
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_snapshot *snap)
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)
--
1.6.5.rc2
--
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