From: Wu Fengguang <fengguang.wu@intel.com>
Subject: Re: 3.2.0-rc5 NULL dereference BUG
Date: Thu, 5 Jan 2012 10:25:25 +0800
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To: Yongqiang Yang <xiaoqiangnk@gmail.com>
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On Thu, Jan 05, 2012 at 10:23:13AM +0800, Yongqiang Yang wrote:
> Hi Fengguang,
>=20
> > [ =C2=A0646.051405] =C2=A0ffff880004ee1978 0000000000000000 0000000=
000000170 0000000000000000
> > [ =C2=A0646.051405] Call Trace:
> > [ =C2=A0646.051405] =C2=A0[<ffffffff81099aa3>] ? sched_clock_local+=
0x12/0x75
> > [ =C2=A0646.051405] =C2=A0[<ffffffff810a5a16>] lock_acquire+0xdd/0x=
10a
> > [ =C2=A0646.051405] =C2=A0[<ffffffff81175de4>] ? create_empty_buffe=
rs+0x4a/0xc1
> > [ =C2=A0646.051405] =C2=A0[<ffffffff8199f623>] _raw_spin_lock+0x36/=
0x69
> > [ =C2=A0646.051405] =C2=A0[<ffffffff81175de4>] ? create_empty_buffe=
rs+0x4a/0xc1
> > [ =C2=A0646.051405] =C2=A0[<ffffffff81175de4>] create_empty_buffers=
+0x4a/0xc1
> > [ =C2=A0646.051405] =C2=A0[<ffffffff811efd2f>] ext4_discard_partial=
_page_buffers_no_lock+0x9f/0x406
> > [ =C2=A0646.051405] =C2=A0[<ffffffff8199ffeb>] ? _raw_spin_unlock+0=
x2b/0x2f
> > [ =C2=A0646.051405] =C2=A0[<ffffffff81170c26>] ? __mark_inode_dirty=
+0x1ac/0x1cc
> > [ =C2=A0646.051405] =C2=A0[<ffffffff811767f3>] ? generic_write_end+=
0x6d/0x7f
> > [ =C2=A0646.051405] =C2=A0[<ffffffff811f15e5>] ext4_da_write_end+0x=
244/0x2ed
> > [ =C2=A0646.051405] =C2=A0[<ffffffff810ffeec>] generic_file_buffere=
d_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: handl=
e
> EOF correctly in ext4_bio_write_page()].   The patches had been merge=
d
> to rc6.

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

Thanks,
=46engguang
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