linux-kernel - Kernel BUG when syncing ext2 if USB stick is removed

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Date:	Thu, 12 May 2011 16:54:40 +0200
From:	Torsten Hilbrich <torsten.hilbrich@...unet.com>
To:	Jan Kara <jack@...e.cz>
CC:	linux-ext4@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Kernel BUG when syncing ext2 if USB stick is removed

The error can be reproduced in both linux-2.6 master
(3568bd9720b4a775f28a718fcbb462ce2f386988) and v2.6.38.6. It cannot be
reproduced in v2.6.38.5, because the error occurs only after:

commit 1f74c190e1e97a38823c07fdc71780580a0fc03f
Author: James Bottomley <James.Bottomley@...e.de>
Date:   Fri Apr 22 10:39:59 2011 -0500

    put stricter guards on queue dead checks

    commit 86cbfb5607d4b81b1a993ff689bbd2addd5d3a9b upstream.

in the 2.6.38 stable line.

Here is the error message for master:

general protection fault: 0000 [#1] SMP
last sysfs file:
CPU 1
Modules linked in:

Pid: 1926, comm: sync Not tainted 2.6.39-rc7+ #39 LENOVO 20077KG/20077KG
RIP: 0010:[<ffffffff811231bf>]  [<ffffffff811231bf>]
__mark_inode_dirty+0x14f/0x200
RSP: 0018:ffff88007bebbe08  EFLAGS: 00010246
RAX: ffff88007d031470 RBX: ffff88007d031408 RCX: ffff88007d031470
RDX: 6b6b6b6b6b6b6b6b RSI: ffffffff81d33f2a RDI: ffffffff82002300
RBP: ffff88007bebbe28 R08: 0000000000000000 R09: 0000000000000000
R10: ffff88007bde3d68 R11: ffff88007c2fba6f R12: ffff88007c350300
R13: ffff88007c350458 R14: 0000000000000000 R15: ffffffff81127e30
FS:  00007f8306063700(0000) GS:ffff88007fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000001f40600 CR3: 000000007b968000 CR4: 00000000000006a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process sync (pid: 1926, threadinfo ffff88007beba000, task ffff88007c610820)
Stack:
 ffff88007d031550 ffffea0000082638 0000000000000000 0000000000000000
 ffff88007bebbe58 ffffffff8112a5ff ffffffff81d3c8d8 ffff88007d223eb0
 ffff880002541400 ffff88007d223eb0 ffff88007bebbe78 ffffffff8112a6b6
Call Trace:
 [<ffffffff8112a5ff>] __set_page_dirty+0x6f/0xc0
 [<ffffffff8112a6b6>] mark_buffer_dirty+0x66/0xa0
 [<ffffffff8117c3ce>] ext2_sync_super+0x8e/0xf0
 [<ffffffff8117c495>] ext2_sync_fs+0x65/0x80
 [<ffffffff81127dfe>] __sync_filesystem+0x5e/0x90
 [<ffffffff81127e4f>] sync_one_sb+0x1f/0x30
 [<ffffffff81100021>] iterate_supers+0x71/0xd0
 [<ffffffff81127e8f>] sys_sync+0x2f/0x70
 [<ffffffff819c69ab>] system_call_fastpath+0x16/0x1b
Code: e8 67 be 89 00 48 8b 05 20 47 ff 00 48 8b 53 70 48 8b 4b 68 48 89
43 50 48 8d 43 68 48 89 51 08 48 89 0a 49 8b 94 24 58 01 00 00
 89 42 08 48 89 53 68 4c 89 6b 70 49 89 84 24 58 01 00 00 fe
RIP  [<ffffffff811231bf>] __mark_inode_dirty+0x14f/0x200
 RSP <ffff88007bebbe08>
---[ end trace 04d7660d6043ca51 ]---

If I parsed the error location correctly, it is the:

  next->prev = prev; // mov %rcx,(%rdx)

statement from __list_del called via __list_del_entry, list_move from
the line:

  list_move(&inode->i_wb_list, &bdi->wb.b_dirty);

in __mark_inode_dirty. rdx seems to be

Here are the steps for reproduction:

1. mount an USB stick with ext2 FS (mount /dev/sdb1 /mnt)
2. open file on USB stick for writing (cat > /mnt/foo)
3. press some return
4. Remove USB stick
5. In another console run sync

I will append the full kernel log (screenlog.0) and the configuration
(config-master) to this mail.

	Torsten



View attachment "screenlog.0" of type "text/plain" (37632 bytes)

View attachment "config-master" of type "text/plain" (82688 bytes)