> On 28-Jun-2021, at 2:41 AM, Bart Van Assche <bvanassche@xxxxxxx> wrote:
>
> The purpose of the WARN_ON_ONCE() statement in dd_insert_request() is to
> verify that dd_prepare_request() cleared rq->elv.priv[0]. Since
> dd_prepare_request() is called during request initialization but not if a
> request is requeued, a warning is triggered if a request is requeued. Fix
> this by removing the WARN_ON_ONCE() statement. This patch suppresses the
> following kernel warning:
>
> WARNING: CPU: 28 PID: 432 at block/mq-deadline-main.c:740 dd_insert_request+0x4d4/0x5b0
> Workqueue: kblockd blk_mq_requeue_work
> Call Trace:
> dd_insert_requests+0xfa/0x130
> blk_mq_sched_insert_request+0x22c/0x240
> blk_mq_requeue_work+0x21c/0x2d0
> process_one_work+0x4c2/0xa70
> worker_thread+0x2e5/0x6d0
> kthread+0x21c/0x250
> ret_from_fork+0x1f/0x30
>
> Reported-by: Sachin Sant <sachinp@xxxxxxxxxxxxxxxxxx>
> Fixes: 08a9ad8bf607 ("block/mq-deadline: Add cgroup support")
> Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
> ---
Thanks for the patch. Fixes the problem for me.
-Sachin
> block/mq-deadline-main.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/block/mq-deadline-main.c b/block/mq-deadline-main.c
> index 9db6da9ef4c6..6f612e6dc82b 100644
> --- a/block/mq-deadline-main.c
> +++ b/block/mq-deadline-main.c
> @@ -740,7 +740,6 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
> dd_count(dd, inserted, prio);
> blkcg = dd_blkcg_from_bio(rq->bio);
> ddcg_count(blkcg, inserted, ioprio_class);
> - WARN_ON_ONCE(rq->elv.priv[0]);
> rq->elv.priv[0] = blkcg;
>
> if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
