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Date: Fri, 17 Dec 2010 09:21:19 -0500
From: Rik van Riel <riel@redhat.com>
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To: Wu Fengguang <fengguang.wu@intel.com>
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>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Greg Thelen <gthelen@google.com>, Minchan Kim <minchan.kim@gmail.com>,
        linux-mm <linux-mm@kvack.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] writeback: skip balance_dirty_pages() for in-memory fs
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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On 12/17/2010 06:21 AM, Wu Fengguang wrote:
> This avoids unnecessary checks and dirty throttling on tmpfs/ramfs.
>
> It also prevents
>
> [  388.126563] BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
>
> in the balance_dirty_pages tracepoint, which will call
>
> 	dev_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>

Acked-by: Rik van Riel <riel@redhat.com>

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