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>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-snap.c | 33 +++++++++++++++++++++++++++++++++
1 files changed, 33 insertions(+), 0 deletions(-)
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 5fd7055..2a9fae9 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -561,6 +561,30 @@ out:
return handover_snap;
}
+static struct dm_snapshot *find_merging_snapshot(struct block_device *origin)
+{
+ struct dm_snapshot *s, *merging_snap = NULL;
+ struct origin *o;
+
+ down_read(&_origins_lock);
+
+ o = __lookup_origin(origin);
+ if (!o)
+ goto out;
+
+ list_for_each_entry(s, &o->snapshots, list) {
+ if (is_merge(s->ti)) {
+ merging_snap = s;
+ break;
+ }
+ }
+
+out:
+ up_read(&_origins_lock);
+
+ return merging_snap;
+}
+
#define min_not_zero(l, r) (((l) == 0) ? (r) : (((r) == 0) ? (l) : min(l, r)))
/*
@@ -732,6 +756,15 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
/* Does snapshot need exceptions handed over to it? */
handover_snap = find_snapshot_using_cow(s);
if (handover_snap) {
+ if (is_merge(s->ti)) {
+ r = -EINVAL;
+ /* Do not allow more than one merging snapshot */
+ if (find_merging_snapshot(s->origin->bdev)) {
+ ti->error = "A snapshot is already merging.";
+ goto bad_load_and_register;
+ }
+ }
+
down_write(&handover_snap->lock);
if (handover_snap->is_handover_source) {
up_write(&handover_snap->lock);
--
1.6.5.2
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