dm io: fix duplicate bio completion due to missing ref count
If only a subset of the devices associated with multiple regions support
a given special operation (eg. DISCARD) then the dec_count() that is
used to set error for the region must increment the io->count.
Otherwise, when the dec_count() is called it can cause the dm-io
caller's bio to be completed multiple times. As was reported against
the dm-mirror target that had mirror legs with a mix of discard
capabilities.
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=196077
Reported-by: Zhang Yi <yizhan@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 3702e50..8d5ca30 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -317,8 +317,8 @@ static void do_region(int op, int op_flags, unsigned region,
else if (op == REQ_OP_WRITE_SAME)
special_cmd_max_sectors = q->limits.max_write_same_sectors;
if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES ||
- op == REQ_OP_WRITE_SAME) &&
- special_cmd_max_sectors == 0) {
+ op == REQ_OP_WRITE_SAME) && special_cmd_max_sectors == 0) {
+ atomic_inc(&io->count);
dec_count(io, region, -EOPNOTSUPP);
return;
}