block: warn if tag is greater than real_max_depth.

In case tag depth is reduced, it is max_depth not real_max_depth.
So we should allow a request with tag >= max_depth, but for a
tag >= real_max_depth, there really should be some problem.

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 2 deletions

diff --git a/block/blk-tag.c b/block/blk-tag.c
index ece65fc4c79b..e74d6d13838f 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -286,12 +286,14 @@ void blk_queue_end_tag(struct request_queue *q, struct request *rq)
 
         BUG_ON(tag == -1);
 
-        if (unlikely(tag >= bqt->real_max_depth))
+        if (unlikely(tag >= bqt->max_depth)) {
                 /*
                  * This can happen after tag depth has been reduced.
-                 * FIXME: how about a warning or info message here?
+                 * But tag shouldn't be larger than real_max_depth.
                  */
+                WARN_ON(tag >= bqt->real_max_depth);
                 return;
+        }
 
         list_del_init(&rq->queuelist);
         rq->cmd_flags &= ~REQ_QUEUED;