linux-kernel - Re: [PATCH 0/7] Change page reference handling semantic of page cache

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Message-ID: <alpine.LSU.2.00.1012291916020.14917@sister.anvils>
Date:	Wed, 29 Dec 2010 19:17:11 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Minchan Kim <minchan.kim@...il.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 0/7] Change page reference handling semantic of page
 cache

On Thu, 23 Dec 2010, Minchan Kim wrote:

> Now we increases page reference on add_to_page_cache but doesn't decrease it
> in remove_from_page_cache. Such asymmetric makes confusing about
> page reference so that caller should notice it and comment why they
> release page reference. It's not good API.
> 
> Long time ago, Hugh tried it[1] but gave up of reason which
> reiser4's drop_page had to unlock the page between removing it from
> page cache and doing the page_cache_release. But now the situation is
> changed. I think at least things in current mainline doesn't have any
> obstacles. The problem is fs or somethings out of mainline.
> If it has done such thing like reiser4, this patch could be a problem but
> they found it when compile time since we remove remove_from_page_cache.
> 
> [1] http://lkml.org/lkml/2004/10/24/140
> 
> The series configuration is following as. 
> 
> [1/7] : This patch introduces new API delete_from_page_cache.
> [2,3,4,5/7] : Change remove_from_page_cache with delete_from_page_cache.
> Intentionally I divide patch per file since someone might have a concern 
> about releasing page reference of delete_from_page_cache in 
> somecase (ex, truncate.c)
> [6/7] : Remove old API so out of fs can meet compile error when build time
> and can notice it.
> [7/7] : Change __remove_from_page_cache with __delete_from_page_cache, too.
> In this time, I made all-in-one patch because it doesn't change old behavior
> so it has no concern. Just clean up patch.
> 
> Minchan Kim (7):
>   [1/7] Introduce delete_from_page_cache
>   [2/7] fuse: Change remove_from_page_cache
>   [3/7] tlbfs: Change remove_from_page_cache
>   [4/7] swap: Change remove_from_page_cache
>   [5/7] truncate: Change remove_from_page_cache
>   [6/7] Good bye remove_from_page_cache
>   [7/7] Change __remove_from_page_cache
> 
>  fs/fuse/dev.c           |    3 +--
>  fs/hugetlbfs/inode.c    |    3 +--
>  include/linux/pagemap.h |    4 ++--
>  mm/filemap.c            |   22 +++++++++++++++++-----
>  mm/shmem.c              |    3 +--
>  mm/truncate.c           |    5 ++---
>  mm/vmscan.c             |    2 +-
>  7 files changed, 25 insertions(+), 17 deletions(-)

Acked-by: Hugh Dickins <hughd@...gle.com>

for all seven: thanks.
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