dm snapshot: permit invalid activation

Allow invalid snapshots to be activated instead of failing.

This allows userspace to reinstate any given snapshot state - for
example after an unscheduled reboot - and clean up the invalid snapshot
at its leisure.

Cc: stable@kernel.org
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 1da41229fbf2..854891d07b59 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -523,9 +523,12 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
         /* Metadata must only be loaded into one table at once */
         r = s->store.read_metadata(&s->store);
-        if (r) {
+        if (r < 0) {
                 ti->error = "Failed to read snapshot metadata";
                 goto bad6;
+        } else if (r > 0) {
+                s->valid = 0;
+                DMWARN("Snapshot is marked invalid.");
         }
 
         bio_list_init(&s->queued_bios);