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>
This commit is contained in:
parent
c66213921c
commit
35bf659b00
|
@ -1080,6 +1080,13 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
|
|||
goto out_unlock;
|
||||
}
|
||||
|
||||
e = lookup_exception(&s->complete, chunk);
|
||||
if (e) {
|
||||
free_pending_exception(pe);
|
||||
remap_exception(s, e, bio, chunk);
|
||||
goto out_unlock;
|
||||
}
|
||||
|
||||
pe = __find_pending_exception(s, pe, chunk);
|
||||
if (!pe) {
|
||||
__invalidate_snapshot(s, -ENOMEM);
|
||||
|
@ -1226,6 +1233,12 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
|
|||
goto next_snapshot;
|
||||
}
|
||||
|
||||
e = lookup_exception(&snap->complete, chunk);
|
||||
if (e) {
|
||||
free_pending_exception(pe);
|
||||
goto next_snapshot;
|
||||
}
|
||||
|
||||
pe = __find_pending_exception(snap, pe, chunk);
|
||||
if (!pe) {
|
||||
__invalidate_snapshot(snap, -ENOMEM);
|
||||
|
|
Loading…
Reference in a new issue