linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: fix dirty page accounting when redirty

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Date:	Sat, 1 Mar 2014 11:26:43 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Chao Yu <chao2.yu@...sung.com>
Cc:	??? <jaegeuk.kim@...sung.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix dirty page accounting when redirty

On Fri, Feb 28, 2014 at 10:12:05AM +0800, Chao Yu wrote:
> We should de-account dirty counters for page when redirty in ->writepage().
> 
> Wu Fengguang described in 'commit 971767caf632190f77a40b4011c19948232eed75':
> "writeback: fix dirtied pages accounting on redirty
> De-account the accumulative dirty counters on page redirty.
> 
> Page redirties (very common in ext4) will introduce mismatch between
> counters (a) and (b)
> 
> a) NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied
> b) NR_WRITTEN, BDI_WRITTEN
> 
> This will introduce systematic errors in balanced_rate and result in
> dirty page position errors (ie. the dirty pages are no longer balanced
> around the global/bdi setpoints)."
> 
> Signed-off-by: Chao Yu <chao2.yu@...sung.com>
> ---
>  fs/f2fs/checkpoint.c |    1 +
>  fs/f2fs/data.c       |    1 +
>  fs/f2fs/node.c       |    1 +
>  3 files changed, 3 insertions(+)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index c8516ee..f069249 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -178,6 +178,7 @@ no_write:
>  redirty_out:
>  	dec_page_count(sbi, F2FS_DIRTY_META);
>  	wbc->pages_skipped++;
> +	account_page_redirty(page);
>  	set_page_dirty(page);
>  	return AOP_WRITEPAGE_ACTIVATE;

redirty_page_for_writepage()?

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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