linux-kernel - Re: [PATCH v2 2/3] move ClearPageReclaim

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Message-ID: <AANLkTikuriwJr-UZg9=WXXwLt-u3sywkzkpZFBV1C4Db@mail.gmail.com>
Date:	Mon, 29 Nov 2010 17:16:01 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ben Gamari <bgamari.foss@...il.com>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...nel.dk>, Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH v2 2/3] move ClearPageReclaim

On Mon, Nov 29, 2010 at 4:29 PM, Wu Fengguang <fengguang.wu@...el.com> wrote:
> On Sun, Nov 28, 2010 at 11:02:56PM +0800, Minchan Kim wrote:
>> fe3cba17 added ClearPageReclaim into clear_page_dirty_for_io for
>> preventing fast reclaiming readahead marker page.
>>
>> In this series, PG_reclaim is used by invalidated page, too.
>> If VM find the page is invalidated and it's dirty, it sets PG_reclaim
>> to reclaim asap. Then, when the dirty page will be writeback,
>> clear_page_dirty_for_io will clear PG_reclaim unconditionally.
>> It disturbs this serie's goal.
>>
>> I think it's okay to clear PG_readahead when the page is dirty, not
>> writeback time. So this patch moves ClearPageReadahead.
>> This patch needs Wu's opinion.
>
> It's a safe change. The possibility and consequence of races are both
> small enough. However the patch could be simplified as follows?

If all of file systems use it, I don't mind it.
Do all of filesystems use it when the page is dirtied?
I was not sure it.(It's why I added Cc. :)
If it doesn't have a problem, I hope so.

Thanks, Wu.

>
> Thanks,
> Fengguang
> ---
>
> --- linux-next.orig/mm/page-writeback.c 2010-11-29 15:14:54.000000000 +0800
> +++ linux-next/mm/page-writeback.c      2010-11-29 15:15:02.000000000 +0800
> @@ -1330,6 +1330,7 @@ int set_page_dirty(struct page *page)
>  {
>        struct address_space *mapping = page_mapping(page);
>
> +       ClearPageReclaim(page);
>        if (likely(mapping)) {
>                int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
>  #ifdef CONFIG_BLOCK
> @@ -1387,7 +1388,6 @@ int clear_page_dirty_for_io(struct page
>
>        BUG_ON(!PageLocked(page));
>
> -       ClearPageReclaim(page);
>        if (mapping && mapping_cap_account_dirty(mapping)) {
>                /*
>                 * Yes, Virginia, this is indeed insane.
>



-- 
Kind regards,
Minchan Kim
--
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