Re: BUG: Bad page state in process (current git)

From: Hugh Dickins <hughd@google.com>
To: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Christoph Lameter <cl@linux.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	"Theodore Ts'o" <tytso@mit.edu>,
	linux-ext4@vger.kernel.org
Subject: Re: BUG: Bad page state in process (current git)
Date: Mon, 15 Nov 2010 13:23:41 -0800	[thread overview]
Message-ID: <AANLkTikWaADzUrqKhZ9gviW8sk8mPjC9kKFJyitvzQmx@mail.gmail.com> (raw)
In-Reply-To: <20101115195439.GA1569@arch.trippelsdorf.de>

On Mon, Nov 15, 2010 at 11:54 AM, Markus Trippelsdorf
<markus@trippelsdorf.de> wrote:
> On 2010.11.15 at 13:38 +0100, Markus Trippelsdorf wrote:
>> On 2010.11.12 at 13:20 +0100, Markus Trippelsdorf wrote:
>> >
>> > Yes. Fortunately the BUG is gone since I pulled the upcoming drm fixes
>>
>> No. I happend again today (with those fixes already applied):
>>
>> BUG: Bad page state in process knode  pfn:7f0a8
>> page:ffffea0001bca4c0 count:0 mapcount:0 mapping:          (null) index:0x0
>> page flags: 0x4000000000000008(uptodate)
>> Pid: 18310, comm: knode Not tainted 2.6.37-rc1-00549-gae712bf-dirty #16
>> Call Trace:
>>  [<ffffffff810a9022>] ? bad_page+0x92/0xe0
>>  [<ffffffff810aa240>] ? get_page_from_freelist+0x4b0/0x570
>>  [<ffffffff8102e50e>] ? apic_timer_interrupt+0xe/0x20
>>  [<ffffffff810aa413>] ? __alloc_pages_nodemask+0x113/0x6b0
>>  [<ffffffff810a2dd4>] ? file_read_actor+0xc4/0x190
>>  [<ffffffff810a4a70>] ? generic_file_aio_read+0x560/0x6b0
>>  [<ffffffff810bdf8d>] ? handle_mm_fault+0x6bd/0x970
>>  [<ffffffff8104b1d0>] ? do_page_fault+0x120/0x410
>>  [<ffffffff810c3d85>] ? do_brk+0x275/0x360
>>  [<ffffffff81452d8f>] ? page_fault+0x1f/0x30
>> Disabling lock debugging due to kernel taint
>
> And another one. But this time it seems to point to ext4:
>
> BUG: Bad page state in process rm  pfn:52e54
> page:ffffea0001222260 count:0 mapcount:0 mapping:          (null) index:0x0
> page flags: 0x4000000000000008(uptodate)
> Pid: 2084, comm: rm Not tainted 2.6.37-rc1-00549-gae712bf-dirty #23
> Call Trace:
>  [<ffffffff810a9022>] ? bad_page+0x92/0xe0
>  [<ffffffff810aa240>] ? get_page_from_freelist+0x4b0/0x570
>  [<ffffffff81142ae6>] ? ext4_ext_put_in_cache+0x46/0x90
>  [<ffffffff810aa413>] ? __alloc_pages_nodemask+0x113/0x6b0
>  [<ffffffff8118f0c7>] ? number.clone.2+0x2b7/0x2f0
>  [<ffffffff810a38d5>] ? find_get_page+0x75/0xb0
>  [<ffffffff810a4011>] ? find_or_create_page+0x51/0xb0
>  [<ffffffff810ff4d7>] ? __getblk+0xd7/0x260
>  [<ffffffff8113158f>] ? ext4_getblk+0x8f/0x1e0
>  [<ffffffff811316ed>] ? ext4_bread+0xd/0x70
>  [<ffffffff811369f4>] ? htree_dirblock_to_tree+0x34/0x190
>  [<ffffffff8113870f>] ? ext4_htree_fill_tree+0x9f/0x250
>  [<ffffffff810e109d>] ? do_filp_open+0x12d/0x5e0
>  [<ffffffff811289ed>] ? ext4_readdir+0x14d/0x5a0
>  [<ffffffff810e4e80>] ? filldir+0x0/0xd0
>  [<ffffffff810e50a8>] ? vfs_readdir+0xa8/0xd0
>  [<ffffffff810e4e80>] ? filldir+0x0/0xd0
>  [<ffffffff810e51b1>] ? sys_getdents+0x81/0xf0
>  [<ffffffff8102dc2b>] ? system_call_fastpath+0x16/0x1b
> Disabling lock debugging due to kernel taint
>
> I don't know. Could a possible bug in linux/fs/ext4/page-io.c be
> responsible for something like this?

I do think you're right: every one of your "Bad page state" reports
has been complaining only about the PageUptodate bit being set, and
that SetPageUpdate() in ext4_end_bio() does look suspicious, coming
after the put_page().

The more suspicious given that other races have been noticed in
precisely that area, and fixed with put_io_page() in the current git
tree.

Perhaps that fixes your problem, but my guess would be not: I suspect
the "if (!partial_write) SetPageUpdate(page);" should be done before
the block (or put_io_page) which does the put_page().

Hugh