On Thu, 31 Jan 2013 01:19:41 -0500 (est), Eric Sandeen wrote:
> On Jan 31, 2013, at 12:13 AM, Miao Xie <mi...@cn.fujitsu.com> wrote:
>
>> On thu, 31 Jan 2013 12:37:49 +0900, Tsutomu Itoh wrote:
>>> Hi,
>>>
>>> In kernel 3.8-rc5, the following panics occurred when the mount was done
>>> by the degraded option.
>>>
>>> # btrfs fi sh /dev/sdc8
>>> Label: none uuid: fc63cd80-5ae2-4fbe-8795-2d526c937a56
>>> Total devices 3 FS bytes used 20.98GB
>>> devid 1 size 9.31GB used 9.31GB path /dev/sdd8
>>> devid 2 size 9.31GB used 9.31GB path /dev/sdc8
>>> *** Some devices missing
>>>
>>> Btrfs v0.20-rc1-37-g91d9eec
>>> # mount -o degraded /dev/sdc8 /test1
>>>
>>> 564 static struct btrfs_worker_thread *find_worker(struct btrfs_workers
>>> *workers)
>>> 565 {
>>> ...
>>> ...
>>> 595 fallback:
>>> 596 fallback = NULL;
>>> 597 /*
>>> 598 * we have failed to find any workers, just
>>> 599 * return the first one we can find.
>>> 600 */
>>> 601 if (!list_empty(&workers->worker_list))
>>> 602 fallback = workers->worker_list.next;
>>> 603 if (!list_empty(&workers->idle_list))
>>> 604 fallback = workers->idle_list.next;
>>> 605 BUG_ON(!fallback); <---------------------- this !
>>> 606 worker = list_entry(fallback,
>>> 607 struct btrfs_worker_thread, worker_list);
>>
>>
>> If worker_list is not empty, we get a worker from this list; if worker_list
>> is empty,
>> it means all the workers in idle_list, we get the worker from idle_list.
>>
>> So the above bug is introduced by the second if sentence. it should be "else
>> if".
>
> else if makes sense, but we cannot reach the BUG_ON unless both lists are
> empty, correct?
You are right, I misread the code.
Thanks
Miao
>
> -Eric
>
>> Thanks
>> Miao
>>
>>>
>>> -Tsutomu
>>>
>>> ===================================================================================
>>>
>>> [ 7913.075890] btrfs: allowing degraded mounts
>>> [ 7913.075893] btrfs: disk space caching is enabled
>>> [ 7913.092031] Btrfs: too many missing devices, writeable mount is not
>>> allowed
>>> [ 7913.092297] ------------[ cut here ]------------
>>> [ 7913.092313] kernel BUG at fs/btrfs/async-thread.c:605!
>>> [ 7913.092326] invalid opcode: 0000 [#1] SMP
>>> [ 7913.092342] Modules linked in: btrfs zlib_deflate crc32c libcrc32c nfsd
>>> lockd nfs_acl auth_rpcgss sunrpc 8021q garp stp llc cpufreq_ondemand
>>> cachefiles fscache ipv6 ext3 jbd dm_mirror dm_region_hash dm_log dm_mod
>>> uinput ppdev iTCO_wdt iTCO_vendor_support parport_pc parport sg
>>> acpi_cpufreq freq_table mperf coretemp kvm pcspkr i2c_i801 i2c_core lpc_ich
>>> mfd_core tg3 ptp pps_core shpchp pci_hotplug i3000_edac edac_core ext4
>>> mbcache jbd2 crc16 sr_mod cdrom sd_mod crc_t10dif pata_acpi ata_piix libata
>>> megaraid_sas scsi_mod floppy [last unloaded: microcode]
>>> [ 7913.092575] CPU 0
>>> [ 7913.092584] Pid: 3673, comm: btrfs-endio-wri Not tainted 3.8.0-rc5 #1
>>> FUJITSU-SV PRIMERGY /D2399
>>> [ 7913.092608] RIP: 0010:[<ffffffffa04670ef>] [<ffffffffa04670ef>]
>>> btrfs_queue_worker+0x10e/0x236 [btrfs]
>>> [ 7913.092663] RSP: 0018:ffff88019fc03c10 EFLAGS: 00010046
>>> [ 7913.092676] RAX: 0000000000000000 RBX: ffff8801967b8a58 RCX:
>>> 0000000000000000
>>> [ 7913.092894] RDX: 0000000000000000 RSI: ffff8801961239b8 RDI:
>>> ffff8801967b8ab8
>>> [ 7913.093116] RBP: ffff88019fc03c50 R08: 0000000000000000 R09:
>>> ffff880198801180
>>> [ 7913.093247] R10: ffffffffa045fda7 R11: 0000000000000003 R12:
>>> 0000000000000000
>>> [ 7913.093247] R13: ffff8801961239b8 R14: ffff8801967b8ab8 R15:
>>> 0000000000000246
>>> [ 7913.093247] FS: 0000000000000000(0000) GS:ffff88019fc00000(0000)
>>> knlGS:0000000000000000
>>> [ 7913.093247] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
>>> [ 7913.093247] CR2: ffffffffff600400 CR3: 000000019575d000 CR4:
>>> 00000000000007f0
>>> [ 7913.093247] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
>>> 0000000000000000
>>> [ 7913.093247] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
>>> 0000000000000400
>>> [ 7913.093247] Process btrfs-endio-wri (pid: 3673, threadinfo
>>> ffff8801939ca000, task ffff880195795b00)
>>> [ 7913.093247] Stack:
>>> [ 7913.093247] ffff8801967b8a88 ffff8801967b8a78 ffff88003fa0a600
>>> ffff8801965ad0c0
>>> [ 7913.093247] ffff88003fa0a600 0000000000000000 0000000000000000
>>> 0000000000000000
>>> [ 7913.096183] ffff88019fc03c60 ffffffffa043e357 ffff88019fc03c70
>>> ffffffff811526aa
>>> [ 7913.096183] Call Trace:
>>> [ 7913.096183] <IRQ>
>>> [ 7913.096183]
>>> [ 7913.096183] [<ffffffffa043e357>] end_workqueue_bio+0x79/0x7b [btrfs]
>>> [ 7913.096183] [<ffffffff811526aa>] bio_endio+0x2d/0x2f
>>> [ 7913.096183] [<ffffffffa045fdb2>] btrfs_end_bio+0x10b/0x122 [btrfs]
>>> [ 7913.096183] [<ffffffff811526aa>] bio_endio+0x2d/0x2f
>>> [ 7913.096183] [<ffffffff811c5e3f>] req_bio_endio+0x96/0x9f
>>> [ 7913.096183] [<ffffffff811c601d>] blk_update_request+0x1d5/0x3a4
>>> [ 7913.096183] [<ffffffff811c620c>] blk_update_bidi_request+0x20/0x6f
>>> [ 7913.096183] [<ffffffff811c7a59>] blk_end_bidi_request+0x1f/0x5d
>>> [ 7913.096183] [<ffffffff811c7ad3>] blk_end_request+0x10/0x12
>>> [ 7913.096183] [<ffffffffa001db50>] scsi_io_completion+0x207/0x4f3
>>> [scsi_mod]
>>> [ 7913.096183] [<ffffffffa0016df9>] scsi_finish_command+0xec/0xf5
>>> [scsi_mod]
>>> [ 7913.096183] [<ffffffffa001df50>] scsi_softirq_done+0xff/0x108 [scsi_mod]
>>> [ 7913.096183] [<ffffffff811ccb3a>] blk_done_softirq+0x7a/0x8e
>>> [ 7913.096183] [<ffffffff810475c3>] __do_softirq+0xd7/0x1ed
>>> [ 7913.096183] [<ffffffff813ead9c>] call_softirq+0x1c/0x30
>>> [ 7913.096183] [<ffffffff81010ab6>] do_softirq+0x46/0x83
>>> [ 7913.096183] [<ffffffff81047363>] irq_exit+0x49/0xb7
>>> [ 7913.096183] [<ffffffff813eafd5>] do_IRQ+0x9d/0xb4
>>> [ 7913.096183] [<ffffffffa0467217>] ? btrfs_queue_worker+0x236/0x236
>>> [btrfs]
>>> [ 7913.096183] [<ffffffff813e2a2d>] common_interrupt+0x6d/0x6d
>>> [ 7913.096183] <EOI>
>>> [ 7913.096183]
>>> [ 7913.096183] [<ffffffff81069a5e>] ? sched_move_task+0x12e/0x13d
>>> [ 7913.096183] [<ffffffff8104a131>] ? ptrace_put_breakpoints+0x1/0x1e
>>> [ 7913.096183] [<ffffffff81044fc2>] ? do_exit+0x3d7/0x89d
>>> [ 7913.096183] [<ffffffffa0467217>] ? btrfs_queue_worker+0x236/0x236
>>> [btrfs]
>>> [ 7913.096183] [<ffffffffa0467217>] ? btrfs_queue_worker+0x236/0x236
>>> [btrfs]
>>> [ 7913.096183] [<ffffffff8105ca20>] kthread+0xbd/0xbd
>>> [ 7913.096183] [<ffffffff8105c963>] ?
>>> kthread_freezable_should_stop+0x65/0x65
>>> [ 7913.096183] [<ffffffff813e99ec>] ret_from_fork+0x7c/0xb0
>>> [ 7913.096183] [<ffffffff8105c963>] ?
>>> kthread_freezable_should_stop+0x65/0x65
>>> [ 7913.096183] Code: 49 89 c7 0f 84 5f ff ff ff 48 8b 43 20 48 3b 45 c8 ba
>>> 00 00 00 00 4c 8b 63 30 48 0f 44 c2 4c 3b 65 c0 4c 0f 44 e0 4d 85 e4 75 04
>>> <0f> 0b eb fe 49 83 ec 28 49 8d 44 24 40 48 89 45 c8 f0 41 ff 44
>>> [ 7913.096183] RIP [<ffffffffa04670ef>] btrfs_queue_worker+0x10e/0x236
>>> [btrfs]
>>> [ 7913.096183] RSP <ffff88019fc03c10>
>>>
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>>
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