diff options
author | Mikulas Patocka <mpatocka@redhat.com> | 2009-04-02 14:55:26 -0400 |
---|---|---|
committer | Alasdair G Kergon <agk@redhat.com> | 2009-04-02 14:55:26 -0400 |
commit | 35bf659b008e83e725dcd30f542e38461dbb867c (patch) | |
tree | 40be2f357f0905573bd4d21ff59e0db3cda26442 | |
parent | c66213921c816f6b1b16a84911618ba9a363b134 (diff) |
dm snapshot: avoid having two exceptions for the same chunk
We need to check if the exception was completed after dropping the lock.
After regaining the lock, __find_pending_exception checks if the exception
was already placed into &s->pending hash.
But we don't check if the exception was already completed and placed into
&s->complete hash. If the process waiting in alloc_pending_exception was
delayed at this point because of a scheduling latency and the exception
was meanwhile completed, we'd miss that and allocate another pending
exception for already completed chunk.
It would lead to a situation where two records for the same chunk exist
and potential data corruption because multiple snapshot I/Os to the
affected chunk could be redirected to different locations in the
snapshot.
Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
-rw-r--r-- | drivers/md/dm-snap.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index eb7291a84203..462750c66319 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c | |||
@@ -1080,6 +1080,13 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, | |||
1080 | goto out_unlock; | 1080 | goto out_unlock; |
1081 | } | 1081 | } |
1082 | 1082 | ||
1083 | e = lookup_exception(&s->complete, chunk); | ||
1084 | if (e) { | ||
1085 | free_pending_exception(pe); | ||
1086 | remap_exception(s, e, bio, chunk); | ||
1087 | goto out_unlock; | ||
1088 | } | ||
1089 | |||
1083 | pe = __find_pending_exception(s, pe, chunk); | 1090 | pe = __find_pending_exception(s, pe, chunk); |
1084 | if (!pe) { | 1091 | if (!pe) { |
1085 | __invalidate_snapshot(s, -ENOMEM); | 1092 | __invalidate_snapshot(s, -ENOMEM); |
@@ -1226,6 +1233,12 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio) | |||
1226 | goto next_snapshot; | 1233 | goto next_snapshot; |
1227 | } | 1234 | } |
1228 | 1235 | ||
1236 | e = lookup_exception(&snap->complete, chunk); | ||
1237 | if (e) { | ||
1238 | free_pending_exception(pe); | ||
1239 | goto next_snapshot; | ||
1240 | } | ||
1241 | |||
1229 | pe = __find_pending_exception(snap, pe, chunk); | 1242 | pe = __find_pending_exception(snap, pe, chunk); |
1230 | if (!pe) { | 1243 | if (!pe) { |
1231 | __invalidate_snapshot(snap, -ENOMEM); | 1244 | __invalidate_snapshot(snap, -ENOMEM); |