[PATCH v2 1/2] blk-mq: fix nr_requests wrong value when modify it from sysfs

[weiping zhang]

if blk-mq use "none" io scheduler, nr_request get a wrong value when
input a number > tag_set->queue_depth. blk_mq_tag_update_depth will get
the smaller one min(nr, set->queue_depth), and then q->nr_request get a
wrong value.

Reproduce:

echo none > /sys/block/nvme0n1/queue/ioscheduler
echo 1000000 > /sys/block/nvme0n1/queue/nr_requests
cat /sys/block/nvme0n1/queue/nr_requests
1000000

Signed-off-by: weiping zhang <zhangweip...@didichuxing.com>
---
 block/blk-mq.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 98a1860..479c35a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2642,8 +2642,12 @@ int blk_mq_update_nr_requests(struct request_queue *q, 
unsigned int nr)
                 * queue depth. This is similar to what the old code would do.
                 */
                if (!hctx->sched_tags) {
-                       ret = blk_mq_tag_update_depth(hctx, &hctx->tags,
-                                                       min(nr, 
set->queue_depth),
+                       if (nr > set->queue_depth) {
+                               ret = -EINVAL;
+                               break;
+                       }
+
+                       ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
                                                        false);
                } else {
                        ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
-- 
2.9.4