dm exception store: fix misordered writes
We must zero the next chunk on disk *before* writing out the current chunk, not
after. Otherwise if the machine crashes at the wrong time, the "end of metadata"
marker may be missing.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: stable@kernel.org
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index fe6cef8..6179bf7 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -611,17 +611,22 @@
return;
/*
+ * If we completely filled the current area, then wipe the next one.
+ */
+ if ((ps->current_committed == ps->exceptions_per_area) &&
+ zero_disk_area(ps, ps->current_area + 1))
+ ps->valid = 0;
+
+ /*
* Commit exceptions to disk.
*/
- if (area_io(ps, WRITE))
+ if (ps->valid && area_io(ps, WRITE))
ps->valid = 0;
/*
* Advance to the next area if this one is full.
*/
if (ps->current_committed == ps->exceptions_per_area) {
- if (zero_disk_area(ps, ps->current_area + 1))
- ps->valid = 0;
ps->current_committed = 0;
ps->current_area++;
zero_memory_area(ps);