Re: [PATCH v2 1/2] blk-mq: fix nr_requests wrong value when modify it from sysfs
From: Jens Axboe <axboe@kernel.dk>
Date: 2017-09-21 16:37:48
On 09/21/2017 09:17 AM, weiping zhang wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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);
What am I missing here? blk_mq_tag_update_depth() should already return -EINVAL for the case where we can't grow the tags. Looks like this patch should simply remove the min(nr, set->queue_depth) and just pass in 'nr'. Should not need the duplicated check for depth. -- Jens Axboe