linux-kernel - Re: [PATCH v7 1/2] blk-throtl: introduce a new flag THROTL_TG

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Date:   Mon, 7 Feb 2022 16:15:06 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Yu Kuai <yukuai3@...wei.com>
Cc:     tj@...nel.org, axboe@...nel.dk, cgroups@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        yi.zhang@...wei.com
Subject: Re: [PATCH v7 1/2] blk-throtl: introduce a new flag
 THROTL_TG_CANCELING

On Fri, Jan 28, 2022 at 04:45:21PM +0800, Yu Kuai wrote:
> If the new flag is set, then the throtl_grp will stop throttling bios.
> Prepare to canceling all throttled bios if the disk is gone.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>  block/blk-throttle.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 7c462c006b26..abc5e506c72d 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -43,8 +43,12 @@
>  static struct workqueue_struct *kthrotld_workqueue;
>  
>  enum tg_state_flags {
> -	THROTL_TG_PENDING	= 1 << 0,	/* on parent's pending tree */
> -	THROTL_TG_WAS_EMPTY	= 1 << 1,	/* bio_lists[] became non-empty */
> +	/* on parent's pending tree */
> +	THROTL_TG_PENDING	= 1 << 0,
> +	/* bio_lists[] became non-empty */
> +	THROTL_TG_WAS_EMPTY	= 1 << 1,
> +	/* starts to cancel all bios, will be set if the disk is deleted */
> +	THROTL_TG_CANCELING	= 1 << 2,
>  };
>  
>  #define rb_entry_tg(node)	rb_entry((node), struct throtl_grp, rb_node)
> @@ -871,7 +875,8 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio,
>  	       bio != throtl_peek_queued(&tg->service_queue.queued[rw]));
>  
>  	/* If tg->bps = -1, then BW is unlimited */
> -	if (bps_limit == U64_MAX && iops_limit == UINT_MAX) {
> +	if ((bps_limit == U64_MAX && iops_limit == UINT_MAX) ||
> +	    tg->flags & THROTL_TG_CANCELING) {
>  		if (wait)
>  			*wait = 0;
>  		return true;
> @@ -974,6 +979,9 @@ static void tg_update_disptime(struct throtl_grp *tg)
>  	unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime;
>  	struct bio *bio;
>  
> +	if (tg->flags & THROTL_TG_CANCELING)
> +		goto update;
> +

The above change and the following one in tg_update_disptime() isn't
needed actually.

Also I'd suggest to fold the two into one patch.


Thanks,
Ming