From mboxrd@z Thu Jan  1 00:00:00 1970
From: Minchan Kim <minchan.kim@gmail.com>
Subject: Re: [PATCH] writeback: skip balance_dirty_pages() for in-memory fs
Date: Sat, 18 Dec 2010 00:34:04 +0900
Message-ID: <AANLkTima=Tqkga6RzWepLt_H6ooqZappcqZB4MKk546J@mail.gmail.com>
References: <20101213144646.341970461@intel.com>
	<20101213150329.002158963@intel.com>
	<20101217021934.GA9525@localhost>
	<alpine.LSU.2.00.1012162239270.23229@sister.anvils>
	<20101217112111.GA8323@localhost>
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Cc: Hugh Dickins <hughd@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@lst.de>,
	Trond Myklebust <Trond.Myklebust@netapp.com>,
	Dave Chinner <david@fromorbit.com>,
	"Theodore Ts'o" <tytso@mit.edu>,
	Chris Mason <chris.mason@oracle.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Mel Gorman <mel@csn.ul.ie>, Rik van Riel <riel@redhat.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	Greg Thelen <gthelen@google.com>,
	linux-mm <linux-mm@kvack.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
To: Wu Fengguang <fengguang.wu@intel.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20101217112111.GA8323@localhost>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

On Fri, Dec 17, 2010 at 8:21 PM, Wu Fengguang <fengguang.wu@intel.com> =
wrote:
> This avoids unnecessary checks and dirty throttling on tmpfs/ramfs.
>
> It also prevents
>
> [ =A0388.126563] BUG: unable to handle kernel NULL pointer dereferenc=
e at 0000000000000050
>
> in the balance_dirty_pages tracepoint, which will call
>
> =A0 =A0 =A0 =A0dev_name(mapping->backing_dev_info->dev)
>
> but shmem_backing_dev_info.dev is NULL.
>
> CC: Hugh Dickins <hughd@google.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>

Is it a material for -stable?

--=20
Kind regards,
Minchan Kim