dm io: fix duplicate bio completion due to missing ref count

snitm · snitm · commit feb7695fe9fb · 2017-06-21T12:04:50.000-04:00
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
@@ -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;
 	}
