linux-kernel - Re: [PATCH 0/2] new APIs to allocate buffer-cache for superblock in non-movable area

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Date:	Thu, 14 Aug 2014 14:23:00 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>, Jan Kara <jack@...e.cz>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org
CC:	Minchan Kim <minchan@...nel.org>, Joonsoo Kim <js1304@...il.com>,
	РЬАЧШЃ <gunho.lee@....com>
Subject: Re: [PATCH 0/2] new APIs to allocate buffer-cache for superblock
 in non-movable area



2014-08-14 ПРШФ 2:12, Gioh Kim ОД Бл:
> Hello,
> 
> This patch try to solve problem that a long-lasting page caches of
> ext4 superblock and journaling of superblock disturb page migration.
> 
> I've been testing CMA feature on my ARM-based platform
> and found that two page caches cannot be migrated.
> They are page caches of superblock of ext4 filesystem and its journaling data.
> 
> Current ext4 reads superblock with sb_bread() that allocates page
> from movable area. But the problem is that ext4 hold the page until
> it is unmounted. If root filesystem is ext4 the page cannot be migrated forever.
> And also the journaling data for the superblock cannot be migreated.
> 
> I introduce a new API for allocating page cache from non-movable area.
> It is useful for ext4/ext3 and others that want to hold page cache for a long time.
> 
> I have 3 patchs:
> 
> 1. Patch 1/3: introduce a new API that create page cache from non-movable area
> 2. Patch 2/3: have ext4 use the new API to read superblock
> 3. Patch 3/3: have jbd/jbd2 use the new API to make journaling of superblock
> 
> This patchset is based on linux-next-20140814.
> 
> Thanks a lot.
> 
> Gioh Kim (3):
>   fs/buffer.c: allocate buffer cache from non-movable area
>   ext4: allocate buffer-cache for superblock in non-movable area
>   jbd-jbd2-allocate-buffer-cache-for-superblock-inode-.patch
> 
>   fs/buffer.c                 |   63 ++++++++++++++++++++++++++++++----
>   fs/ext4/super.c             |    6 +--
>   fs/jbd/journal.c            |    2 -
>   fs/jbd2/journal.c           |    2 -
>   include/linux/buffer_head.h |   10 +++++
>   5 files changed, 71 insertions(+), 12 deletions(-)
> 

I'm sorry to forget mentioning that this is 2nd version of https://lkml.org/lkml/2014/7/22/34.


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