[PATCH] block: Warn if tag is greater than real_max_depth.

[PATCH] block: Warn if tag is greater than real_max_depth.

[Tao Ma]

From: Tao Ma <boyu.mt@taobao.com>

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.

Cc: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
---
 block/blk-tag.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/block/blk-tag.c b/block/blk-tag.c
index ece65fc..e74d6d1 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;
-- 
1.7.1