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>

diff --git a/block/blk-tag.c b/block/blk-tag.c
index ece65fc..e74d6d1 100644 (file)
--- 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;