[Bug 316355] [NEW] Xen dom0 oops when using LVM: "NULL pointer dereference"

[Gordon Syme]

Public bug reported:

I am using Xen with my images stored on LVM volumes. Generally , when
provisioning a new domU I snapshot the image filesystem and use that for
the domU filesystem.

I occasionally get these oopses when removing the snapshot volume after
shutting down the domU. Once it has occurred I need to reboot before any
LVM related operations will return.

The 2.6.24-22-xen kernel does not seem to be very stable. I am seeing
these LVM related oopses fairly frequently (mostly to do with running MS
Windows 2003 Server with HVM). I also have the occasional dom0 kernel
panic when performing operations with heavy disk IO (such as dd:ing one
filesystem to another).

Relevant portion of dmesg, full log also attached:

[267304.050713] BUG: unable to handle kernel NULL pointer dereference at virtual address 00000127
[267304.050770] printing eip: c01a8cc5
[267304.050795] 2bb2d000 -> *pde = 00000001:096f3001
[267304.050822] 264f3000 -> *pme = 00000000:00000000
[267304.050849] Oops: 0000 [#1] SMP 
[267304.050879] Modules linked in: tun af_packet bridge iptable_filter ip_tables x_tables parport_pc lp parport loop ipv6 serio_raw psmouse button pcspkr 8250_pnp 8250 serial_core dcdbas shpchp pci_hotplug evdev iTCO_wdt iTCO_vendor_support dm_multipath ext3 jbd mbcache sg sr_mod cdrom sd_mod ata_generic usbhid hid ata_piix pata_acpi libata scsi_mod ehci_hcd tg3 uhci_hcd usbcore dm_mirror dm_snapshot dm_mod thermal processor fan fuse
[267304.051167] 
[267304.051188] Pid: 213, comm: pdflush Not tainted (2.6.24-22-xen #1)
[267304.051218] EIP: 0061:[<c01a8cc5>] EFLAGS: 00010297 CPU: 0
[267304.051254] EIP is at __block_write_full_page+0xe5/0x350
[267304.051287] EAX: c2028140 EBX: 000be4d1 ECX: 00000000 EDX: 000be4d0
[267304.051317] ESI: 00000000 EDI: 00000127 EBP: ed002270 ESP: c1021de0
[267304.051346]  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0069
[267304.051374] Process pdflush (pid: 213, ti=c1020000 task=ed5a4070 task.ti=c1020000)
[267304.051406] Stack: 00000005 00000110 c1021e84 c1f8d980 c01ad250 c1f8d980 00000000 001bffff 
[267304.051474]        00000000 c0477178 00001000 00000001 ed002270 c1f8d980 00000000 c01a9027 
[267304.051542]        c1021f74 f578e000 c1021f74 c01ad250 c1f8d980 ed002314 0000000b c1021f74 
[267304.051611] Call Trace:
[267304.051661]  [<c01ad250>] blkdev_get_block+0x0/0x70
[267304.051692]  [<c01a9027>] block_write_full_page+0xf7/0x100
[267304.051724]  [<c01ad250>] blkdev_get_block+0x0/0x70
[267304.051754]  [<c01636d8>] __writepage+0x8/0x30
[267304.051784]  [<c0163d6f>] write_cache_pages+0x21f/0x310
[267304.051815]  [<c01636d0>] __writepage+0x0/0x30
[267304.051847]  [<c0163e80>] generic_writepages+0x20/0x30
[267304.051877]  [<c0163ebb>] do_writepages+0x2b/0x50
[267304.051907]  [<c01a2ad9>] __writeback_single_inode+0x89/0x320
[267304.051938]  [<ee09e2cd>] dm_table_any_congested+0xd/0x60 [dm_mod]
[267304.051977]  [<ee09e2e1>] dm_table_any_congested+0x21/0x60 [dm_mod]
[267304.052013]  [<c01a310f>] sync_sb_inodes+0x19f/0x270
[267304.052044]  [<c01a33f9>] writeback_inodes+0x89/0xc0
[267304.052074]  [<c0164925>] wb_kupdate+0x85/0xf0
[267304.052104]  [<c0164dd0>] pdflush+0x0/0x250
[267304.052132]  [<c0164f16>] pdflush+0x146/0x250
[267304.052161]  [<c01648a0>] wb_kupdate+0x0/0xf0
[267304.052190]  [<c013b7b2>] kthread+0x42/0x70
[267304.052220]  [<c013b770>] kthread+0x0/0x70
[267304.052248]  [<c0105bb7>] kernel_thread_helper+0x7/0x10
[267304.052279]  =======================
[267304.054071] Code: 24 24 eb 21 77 06 3b 5c 24 1c 76 1f f0 0f ba 37 01 f0 0f ba 2f 00 8b 7f 04 39 7c 24 24 74 68 83 c3 01 83 d6 00 3b 74 24 20 73 d9 <8b> 07 a8 20 75 e5 8b 07 a8 02 74 df 8b 54 24 28 39 57 14 0f 85 
[267304.054333] EIP: [<c01a8cc5>] __block_write_full_page+0xe5/0x350 SS:ESP 0069:c1021de0
[267304.054846] ---[ end trace c4666ba89cf2be08 ]---

$ uname -a
Linux potenza 2.6.24-22-xen #1 SMP Mon Nov 24 21:30:37 UTC 2008 i686 GNU/Linux

$ cat /proc/version_signature
Ubuntu 2.6.24-4.6-generic

** Affects: linux-meta (Ubuntu)
     Importance: Undecided
         Status: New

-- 
Xen dom0 oops when using LVM: "NULL pointer dereference"
https://bugs.launchpad.net/bugs/316355
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