[Btrfs-devel] Oops

[Chris Mason]

On Fri, 7 Dec 2007 19:27:43 +0100
Christian Hesse <list at eworm.de> wrote:

> Hello everybody,
> 
> I've my Gentoo's /usr/portage on a loopback btrfs. Just wanted to
> sync and got an oops. I've a rsync and a ls process in status D now.
> The system has been in suspend (tuxonice 3.0-rc3) with mounted btrfs,
> perhaps that is related?

Could be, but only if other filesystems get problems during suspend as
well.

Which version of btrfs was used to format this disk, and which one was
in use when you got the oops?

You're oopsing because the parent pointer for btrfs_cow_block was null,
but the buffer you were trying to cow wasn't the root.  That's not
supposed to happen ;)

-chris

> 
> Dec  7 19:18:38 revo BUG: unable to handle kernel NULL pointer
> dereference at virtual address 0000000c
> Dec  7 19:18:38 revo printing eip: b01dcd24 *pde = 00000000
> Dec  7 19:18:38 revo Oops: 0000 [#1] SMP
> Dec  7 19:18:38 revo Modules linked in: iwl3945 vboxdrv
> Dec  7 19:18:38 revo
> Dec  7 19:18:38 revo Pid: 9464, comm: rsync Not tainted (2.6.24-rc4
> #1) Dec  7 19:18:38 revo EIP: 0060:[<b01dcd24>] EFLAGS: 00210282 CPU:
> 0 Dec  7 19:18:38 revo EIP is at btrfs_set_key_blockptr+0x14/0x100
> Dec  7 19:18:38 revo EAX: 00000000 EBX: 00000060 ECX: 10006000 EDX:
> 0000004f Dec  7 19:18:38 revo ESI: 00000000 EDI: eb1293e4 EBP:
> eec7cbd4 ESP: c4d99c34 Dec  7 19:18:38 revo dhcpcd[8448]: wlan0:
> renewing lease of 192.168.182.74 Dec  7 19:18:38 revo DS: 007b ES:
> 007b FS: 00d8 GS: 0033 SS: 0068 Dec  7 19:18:38 revo Process rsync
> (pid: 9464, ti=c4d98000 task=e0544ab0 task.ti=c4d98000)
> Dec  7 19:18:38 revo Stack: 00000000 eb1293e4 eec7c6f4 06040048
> 00000000 20000000 000000dd 00000000
> Dec  7 19:18:38 revo 00000000 00000000 00000000 eb1293e4 b01bf3e7
> 10006000 00000000 00000000
> Dec  7 19:18:38 revo 00000000 da25be70 ee8e1400 eec7c6f4 00000000
> 000001df 00000000 eb1293e4
> Dec  7 19:18:38 revo Call Trace:
> Dec  7 19:18:38 revo [<b01bf3e7>] __btrfs_cow_block+0x1c7/0x390
> Dec  7 19:18:38 revo [<b01bf726>] btrfs_cow_block+0x176/0x1a0
> Dec  7 19:18:38 revo [<b01c1303>] btrfs_search_slot+0x103/0xe70
> Dec  7 19:18:38 revo [<b02c5965>] dma_pool_alloc+0x155/0x1f0
> Dec  7 19:18:38 revo [<b0121d7b>] enqueue_entity+0x2b/0x60
> Dec  7 19:18:38 revo [<b0121dd7>] enqueue_task_fair+0x27/0x30
> Dec  7 19:18:38 revo [<b0120b72>] enqueue_task+0x12/0x30
> Dec  7 19:18:38 revo [<b0122d6e>] try_to_wake_up+0x4e/0x2b0
> Dec  7 19:18:38 revo [<b01c9168>] btrfs_lookup_inode+0x38/0xc0
> Dec  7 19:18:38 revo [<b01cd4c5>] btrfs_update_inode+0x45/0xc0
> Dec  7 19:18:38 revo [<b01cf329>] btrfs_dirty_inode+0x49/0x80
> Dec  7 19:18:38 revo [<b019e950>] __mark_inode_dirty+0x30/0x180
> Dec  7 19:18:38 revo [<b0196197>] inode_setattr+0xb7/0x180
> Dec  7 19:18:38 revo [<b01cee9e>] btrfs_setattr+0x3e/0x2a0
> Dec  7 19:18:38 revo [<b01712e2>] handle_mm_fault+0xf2/0x570
> Dec  7 19:18:38 revo [<b019633c>] notify_change+0xdc/0x2c0
> Dec  7 19:18:38 revo [<b01a1611>] do_utimes+0x161/0x250
> Dec  7 19:18:38 revo [<b01712e2>] handle_mm_fault+0xf2/0x570
> Dec  7 19:18:38 revo [<b01a1721>] sys_futimesat+0x21/0xa0
> Dec  7 19:18:38 revo [<b01a17bf>] sys_utimes+0x1f/0x30
> Dec  7 19:18:38 revo [<b0104256>] sysenter_past_esp+0x5f/0x85
> Dec  7 19:18:38 revo =======================
> Dec  7 19:18:38 revo Code: 28 8b 74 24 2c 8b 7c 24 30 83 c4 34 c3 8d
> 76 00 8d bc 27 00 00 00 00 83 ec 30 89 5c 24 24 8d 5a 11 89 74 24 28 8
> 9 c6 89 7c 24 2c <8b> 78 0c 85 ff 74 45 8b 48 14 39 cb 72 3e 89 c8 83
> c2 19 03 46
> Dec  7 19:18:38 revo EIP: [<b01dcd24>]
> btrfs_set_key_blockptr+0x14/0x100 SS:ESP 0068:c4d99c34
> 
> Just wondering, is it safe to mount a btrfs root when a subvolume is
> already mounted?

Should be, but could you please send along the exact sequence of
commands you ran?

-chris