linux-kernel - Re: [PATCH 38/51] writeback: make laptop_mode_timer_fn() handle multiple bdi

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Date:	Wed, 1 Jul 2015 09:32:40 +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 38/51] writeback: make laptop_mode_timer_fn() handle
 multiple bdi_writeback's

On Fri 22-05-15 17:13:52, Tejun Heo wrote:
> For cgroup writeback support, all bdi-wide operations should be
> distributed to all its wb's (bdi_writeback's).
> 
> This patch updates laptop_mode_timer_fn() so that it invokes
> wb_start_writeback() on all wb's rather than just the root one.  As
> the intent is writing out all dirty data, there's no reason to split
> the number of pages to write.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Jan Kara <jack@...e.cz>

Looks good. You can add:

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

								Honza

> ---
>  mm/page-writeback.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 6301af2..682e3a6 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1723,14 +1723,20 @@ void laptop_mode_timer_fn(unsigned long data)
>  	struct request_queue *q = (struct request_queue *)data;
>  	int nr_pages = global_page_state(NR_FILE_DIRTY) +
>  		global_page_state(NR_UNSTABLE_NFS);
> +	struct bdi_writeback *wb;
> +	struct wb_iter iter;
>  
>  	/*
>  	 * We want to write everything out, not just down to the dirty
>  	 * threshold
>  	 */
> -	if (bdi_has_dirty_io(&q->backing_dev_info))
> -		wb_start_writeback(&q->backing_dev_info.wb, nr_pages, true,
> -				   WB_REASON_LAPTOP_TIMER);
> +	if (!bdi_has_dirty_io(&q->backing_dev_info))
> +		return;
> +
> +	bdi_for_each_wb(wb, &q->backing_dev_info, &iter, 0)
> +		if (wb_has_dirty_io(wb))
> +			wb_start_writeback(wb, nr_pages, true,
> +					   WB_REASON_LAPTOP_TIMER);
>  }
>  
>  /*
> -- 
> 2.4.0
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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