linux-kernel - Re: [RFC 5/5] truncate: Remove unnecessary page release

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Message-ID: <AANLkTimaW7X6w2e=4SvynHQHO-Kv3wXGv4_NCKDsuYRR@mail.gmail.com>
Date:	Mon, 20 Dec 2010 11:27:48 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [RFC 5/5] truncate: Remove unnecessary page release

On Mon, Dec 20, 2010 at 11:21 AM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
>> This patch series changes remove_from_page_cache's page ref counting
>> rule. page cache ref count is decreased in remove_from_page_cache.
>> So we don't need call again in caller context.
>>
>> Cc: Nick Piggin <npiggin@...e.de>
>> Cc: Al Viro <viro@...iv.linux.org.uk>
>> Cc: linux-mm@...ck.org
>> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
>> ---
>>  mm/truncate.c |    1 -
>>  1 files changed, 0 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/truncate.c b/mm/truncate.c
>> index 9ee5673..8decb93 100644
>> --- a/mm/truncate.c
>> +++ b/mm/truncate.c
>> @@ -114,7 +114,6 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
>>        * calls cleancache_put_page (and note page->mapping is now NULL)
>>        */
>>       cleancache_flush_page(mapping, page);
>> -     page_cache_release(page);       /* pagecache ref */
>>       return 0;
>
> Do we _always_ have stable page reference here? IOW, I can assume

I think so.
Because the page is locked so caller have to hold a ref to unlock it.

> cleancache_flush_page() doesn't cause NULL deref?
>
>
>
>



-- 
Kind regards,
Minchan Kim
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