linux-kernel - Re: [PATCH 29/51] writeback, blkcg: propagate non-root blkcg congestion state

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Date:	Tue, 30 Jun 2015 17:03:24 +0200
From:	Jan Kara <jack@...e.cz>
To:	Tejun Heo <tj@...nel.org>
Cc:	axboe@...nel.dk, linux-kernel@...r.kernel.org, jack@...e.cz,
	hch@...radead.org, hannes@...xchg.org,
	linux-fsdevel@...r.kernel.org, vgoyal@...hat.com,
	lizefan@...wei.com, cgroups@...r.kernel.org, linux-mm@...ck.org,
	mhocko@...e.cz, clm@...com, fengguang.wu@...el.com,
	david@...morbit.com, gthelen@...gle.com, khlebnikov@...dex-team.ru
Subject: Re: [PATCH 29/51] writeback, blkcg: propagate non-root blkcg
 congestion state

On Fri 22-05-15 17:13:43, Tejun Heo wrote:
> Now that bdi layer can handle per-blkcg bdi_writeback_congested state,
> blk_{set|clear}_congested() can propagate non-root blkcg congestion
> state to them.
> 
> This can be easily achieved by disabling the root_rl tests in
> blk_{set|clear}_congested().  Note that we still need those tests when
> !CONFIG_CGROUP_WRITEBACK as otherwise we'll end up flipping root blkcg
> wb's congestion state for events happening on other blkcgs.
> 
> v2: Updated for bdi_writeback_congested.

Looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.com>

								Honza

> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> ---
>  block/blk-core.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index b457c4f..cf6974e 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -65,23 +65,26 @@ static struct workqueue_struct *kblockd_workqueue;
>  
>  static void blk_clear_congested(struct request_list *rl, int sync)
>  {
> -	if (rl != &rl->q->root_rl)
> -		return;
>  #ifdef CONFIG_CGROUP_WRITEBACK
>  	clear_wb_congested(rl->blkg->wb_congested, sync);
>  #else
> -	clear_wb_congested(rl->q->backing_dev_info.wb.congested, sync);
> +	/*
> +	 * If !CGROUP_WRITEBACK, all blkg's map to bdi->wb and we shouldn't
> +	 * flip its congestion state for events on other blkcgs.
> +	 */
> +	if (rl == &rl->q->root_rl)
> +		clear_wb_congested(rl->q->backing_dev_info.wb.congested, sync);
>  #endif
>  }
>  
>  static void blk_set_congested(struct request_list *rl, int sync)
>  {
> -	if (rl != &rl->q->root_rl)
> -		return;
>  #ifdef CONFIG_CGROUP_WRITEBACK
>  	set_wb_congested(rl->blkg->wb_congested, sync);
>  #else
> -	set_wb_congested(rl->q->backing_dev_info.wb.congested, sync);
> +	/* see blk_clear_congested() */
> +	if (rl == &rl->q->root_rl)
> +		set_wb_congested(rl->q->backing_dev_info.wb.congested, sync);
>  #endif
>  }
>  
> -- 
> 2.4.0
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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