linux-kernel - Re: [PATCH 2/2] mm: make do

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Date:	Fri, 3 Feb 2012 21:38:23 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Amit Sahrawat <amit.sahrawat83@...il.com>
Cc:	Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Johannes Weiner <jweiner@...hat.com>,
	Amit Sahrawat <a.sahrawat@...sung.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: make do_writepages() use plugging

On Fri, Feb 03, 2012 at 06:57:06PM +0530, Amit Sahrawat wrote:
> This will cover all the invocations for writepages to be called with
> plugging support.
 
Thanks.  I'll test it on the major filesystems. But would you
name a few filesystems that are expected to benefit from it?
It's not obvious because some FS ->writepages eventually calls
generic_writepages() which already does plugging.

Thanks,
Fengguang

> Signed-off-by: Amit Sahrawat <a.sahrawat@...sung.com>
> ---
>  mm/page-writeback.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 363ba70..2bea32c 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1866,14 +1866,18 @@ EXPORT_SYMBOL(generic_writepages);
>  
>  int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
>  {
> +	struct blk_plug plug;
>  	int ret;
>  
>  	if (wbc->nr_to_write <= 0)
>  		return 0;
> +
> +	blk_start_plug(&plug);
>  	if (mapping->a_ops->writepages)
>  		ret = mapping->a_ops->writepages(mapping, wbc);
>  	else
>  		ret = generic_writepages(mapping, wbc);
> +	blk_finish_plug(&plug);
>  	return ret;
>  }
>  
> -- 
> 1.7.2.3
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