On Sun, 2017-09-03 at 21:46 +0800, 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 <zhangweiping@xxxxxxxxxxxxxxx>
> ---
> block/blk-mq.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index f84d145..8303e5e 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2622,8 +2622,11 @@ 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) {
> + nr = set->queue_depth;
> + pr_warn("reduce nr_request to %u\n", nr);
> + }
> + ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
> false);
> } else {
> ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
Shouldn't this code return -EINVAL or -ERANGE if 'nr' is too large? That will help to
keep user space code simple that updates the queue depth.
Thanks,
Bart.
