From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 22 Sep 2017 01:09:05 +0800 From: weiping zhang To: Jens Axboe CC: Subject: Re: [PATCH v2 1/2] blk-mq: fix nr_requests wrong value when modify it from sysfs Message-ID: <20170921170905.GA2009@localhost.didichuxing.com> References: <0dcb22e96bf2c3064c88dd554d6ac9eb95991a54.1506006064.git.zhangweiping@didichuxing.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: Return-Path: zhangweiping@didichuxing.com List-ID: On Thu, Sep 21, 2017 at 10:37:48AM -0600, Jens Axboe wrote: > On 09/21/2017 09:17 AM, weiping zhang wrote: > > 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 > > --- > > 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. > Ya, you are right, I will send V3 later. Thanks