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Date: Thu, 5 Jan 2012 10:25:25 +0800
From: Wu Fengguang <fengguang.wu@intel.com>
To: Yongqiang Yang <xiaoqiangnk@gmail.com>
Cc: "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: 3.2.0-rc5 NULL dereference BUG
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On Thu, Jan 05, 2012 at 10:23:13AM +0800, Yongqiang Yang wrote:
> Hi Fengguang,
> 
> > [  646.051405]  ffff880004ee1978 0000000000000000 0000000000000170 0000000000000000
> > [  646.051405] Call Trace:
> > [  646.051405]  [<ffffffff81099aa3>] ? sched_clock_local+0x12/0x75
> > [  646.051405]  [<ffffffff810a5a16>] lock_acquire+0xdd/0x10a
> > [  646.051405]  [<ffffffff81175de4>] ? create_empty_buffers+0x4a/0xc1
> > [  646.051405]  [<ffffffff8199f623>] _raw_spin_lock+0x36/0x69
> > [  646.051405]  [<ffffffff81175de4>] ? create_empty_buffers+0x4a/0xc1
> > [  646.051405]  [<ffffffff81175de4>] create_empty_buffers+0x4a/0xc1
> > [  646.051405]  [<ffffffff811efd2f>] ext4_discard_partial_page_buffers_no_lock+0x9f/0x406
> > [  646.051405]  [<ffffffff8199ffeb>] ? _raw_spin_unlock+0x2b/0x2f
> > [  646.051405]  [<ffffffff81170c26>] ? __mark_inode_dirty+0x1ac/0x1cc
> > [  646.051405]  [<ffffffff811767f3>] ? generic_write_end+0x6d/0x7f
> > [  646.051405]  [<ffffffff811f15e5>] ext4_da_write_end+0x244/0x2ed
> > [  646.051405]  [<ffffffff810ffeec>] generic_file_buffered_write+0x183/0x22d
> It seems that you are running in to several problems related to
> discard_page_buffers_no_lock in write_end.  The problems had been
> fixed by following patches [ext4: avoid potential hang in
> mpage_submit_io() when blocksize < pagesize], [ext4: correctly handle
> pages w/o buffers in ext4_discard_partial_buffers()] and [ext4: handle
> EOF correctly in ext4_bio_write_page()].   The patches had been merged
> to rc6.

That's great! I'll test rc7+.

Thanks,
Fengguang