[Xen-devel] kernel BUG at mm/swapfile.c:2524

[Peter Sandin <psandin@xxxxxxxxxx>]

Hello,

We've got some 2.6.38 domUs that are hitting a bug in mm/swapfile.c. The issue 
has only cropped up since we have moved to 2.6.38. This issue has happened on 
multiple separate physical machines. I've attached the trace from one instance 
here, additional instances can be found along with a copy of the domU kernel 
image and configuration at:

http://thesandins.net/xen/2.6.38/

------------[ cut here ]------------
kernel BUG at mm/swapfile.c:2524!
invalid opcode: 0000 [#1] SMP
last sysfs file: /sys/devices/vbd-51728/block/xvdb/stat
Modules linked in:

Pid: 539, comm: apache2 Not tainted 2.6.38-linode31 #1
EIP: 0061:[<c01a36b6>] EFLAGS: 00010246 CPU: 0
EIP is at swap_count_continued+0x176/0x180
EAX: f57ba5f8 EBX: ed3c8f00 ECX: f57ba000 EDX: 00000000
ESI: ed3c5320 EDI: 00000080 EBP: 000005f8 ESP: eb80be80
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0069
Process apache2 (pid: 539, ti=eb80a000 task=cc472be0 task.ti=eb80a000)
Stack:
 ec8e68c0 000195f8 00000040 00000000 c01a37b1 000195f8 ec96ae20 ed14b000
 00000000 c01a3a18 00000000 c01955cc 00000000 80000007 00000000 c0106314
 00000023 ecf7ac4c 000195f8 ca6e0290 00000000 ffffffe8 b883d664 00000000
Call Trace:
 [<c01a37b1>] ? swap_entry_free+0xf1/0x120
 [<c01a3a18>] ? swap_free+0x18/0x30
 [<c01955cc>] ? handle_pte_fault+0x49c/0xac0
 [<c0106314>] ? check_events+0x8/0xc
 [<c0196e91>] ? handle_mm_fault+0x101/0x1a0
 [<c011e81b>] ? do_page_fault+0xfb/0x3e0
 [<c063f390>] ? _raw_spin_lock_irq+0x10/0x20
 [<c063fcd6>] ? error_code+0x5a/0x60
 [<c013f397>] ? sys_rt_sigaction+0x77/0xa0
 [<c011e720>] ? do_page_fault+0x0/0x3e0
 [<c063fcd6>] ? error_code+0x5a/0x60
 [<c0630000>] ? sctp_sockaddr_af+0x20/0x90
 [<c011e720>] ? do_page_fault+0x0/0x3e0
Code: ff 89 d8 e8 cd f7 f7 ff 01 e8 8d 76 00 c6 00 00 ba 01 00 00 00 eb b2 89 
f8 3c 80 0f 94 c0 e9 b
9 fe ff ff 0f 0b eb fe 0f 0b eb fe <0f> 0b eb fe 0f 0b eb fe 66 90 83 ec 10 89 
1c 24 89 c3 89 74 24
EIP: [<c01a36b6>] swap_count_continued+0x176/0x180 SS:ESP 0069:eb80be80
---[ end trace 41e4a2572fe1ada6 ]---

I've looked at the section of code that is generating the the fault, but I'm a 
bit over my head. Does this look like it is a Xen specific issue, or something 
that would be better addressed on the LKML? Any insight you can provide on the 
source or a fix for this issue would be appreciated.

Thanks,
Peter
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