On Fri, Aug 09, 2013 at 09:52:19AM -0600, Jens Axboe wrote:

On 08/09/2013 09:07 AM, Alexander Gordeev wrote:

quoted

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index dcbc2a4..b131a48 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c

@@ -468,10 +468,9 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
 	 * Rest of the tags start at the queue list
 	 */
 	tags->nr_free = 0;
-	while (nr_tags - tags->nr_reserved) {
+	while (nr_tags--) {
 		tags->freelist[tags->nr_free] = tags->nr_free +
 							tags->nr_reserved;
-		nr_tags--;
 		tags->nr_free++;
 	}

I misremembered, just checked the code. I think I used to have it like I
described, but changed it since I thought it would be more logical to
pass in full depth, and then what part of that is reserved. Looking at
the current code, your patch looks correct as-is.

Ok, then a whole series "[PATCH 0/3] blk-mq: Avoid effects of a weird queue
depth" (I posted earlier in a separate thread) should make sense. Besides
the hunk above it limits the per-cpu cache size and sanity-checks total vs
reserved length. I can resubmit if you want.

-- 
Jens Axboe

-- 
Regards,
Alexander Gordeev
agordeev@redhat.com