Re: fs: GPF in locked_inode_to_wb_and_lock_list

[Dmitry Vyukov <dvyukov@google.com>]

On Thu, Apr 21, 2016 at 11:10 AM, Andrey Ryabinin
<ryabinin.a.a@gmail.com> wrote:
> 2016-04-21 11:25 GMT+03:00 Dmitry Vyukov <dvyukov@google.com>:
>> On Wed, Apr 20, 2016 at 11:14 PM, Tejun Heo <tj@kernel.org> wrote:
>>> Hello, Dmitry.
>>>
>>> On Mon, Apr 18, 2016 at 11:44:11AM +0200, Dmitry Vyukov wrote:
>>>
>>>> general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN
>>> ...
>>>> RIP: 0010:[<ffffffff818884d2>]  [<ffffffff818884d2>]
>>>> locked_inode_to_wb_and_lock_list+0xa2/0x750
>>>> RSP: 0018:ffff88006cdaf7d0  EFLAGS: 00010246
>>>> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88006ccf2050
>>>> RDX: 0000000000000000 RSI: 000000114c8a8484 RDI: 0000000000000286
>>>> RBP: ffff88006cdaf820 R08: ffff88006ccf1840 R09: 0000000000000000
>>>> R10: 000229915090805f R11: 0000000000000001 R12: ffff88006a72f5e0
>>>> R13: dffffc0000000000 R14: ffffed000d4e5eed R15: ffffffff8830cf40
>>>> FS:  0000000000000000(0000) GS:ffff88006d500000(0000) knlGS:0000000000000000
>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> CR2: 0000000003301bf8 CR3: 000000006368f000 CR4: 00000000000006e0
>>>> DR0: 0000000000001ec9 DR1: 0000000000000000 DR2: 0000000000000000
>>>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
>>>> Stack:
>>>>  ffff88006a72f680 ffff88006a72f768 ffff8800671230d8 03ff88006cdaf948
>>>>  ffff88006a72f668 ffff88006a72f5e0 ffff8800671230d8 ffff88006cdaf948
>>>>  ffff880065b90cc8 ffff880067123100 ffff88006cdaf970 ffffffff8188e12e
>>>> Call Trace:
>>>>  [<     inline     >] inode_to_wb_and_lock_list fs/fs-writeback.c:309
>>>>  [<ffffffff8188e12e>] writeback_sb_inodes+0x4de/0x1250 fs/fs-writeback.c:1554
>>>>  [<ffffffff8188efa4>] __writeback_inodes_wb+0x104/0x1e0 fs/fs-writeback.c:1600
>>>>  [<ffffffff8188f9ae>] wb_writeback+0x7ce/0xc90 fs/fs-writeback.c:1709
>>>>  [<     inline     >] wb_do_writeback fs/fs-writeback.c:1844
>>>>  [<ffffffff81891079>] wb_workfn+0x2f9/0x1000 fs/fs-writeback.c:1884
>>>>  [<ffffffff813bcd1e>] process_one_work+0x78e/0x15c0 kernel/workqueue.c:2094
>>>>  [<ffffffff813bdc2b>] worker_thread+0xdb/0xfc0 kernel/workqueue.c:2228
>>>>  [<ffffffff813cdeef>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
>>>>  [<ffffffff867bc5d2>] ret_from_fork+0x22/0x50 arch/x86/entry/entry_64.S:392
>>>> Code: 05 94 4a a8 06 85 c0 0f 85 03 03 00 00 e8 07 15 d0 ff 41 80 3e
>>>> 00 0f 85 64 06 00 00 49 8b 9c 24 88 01 00 00 48 89 d8 48 c1 e8 03 <42>
>>>> 80 3c 28 00 0f 85 17 06 00 00 48 8b 03 48 83 c0 50 48 39 c3
>>>> RIP  [<     inline     >] wb_get include/linux/backing-dev-defs.h:212
>>>> RIP  [<ffffffff818884d2>] locked_inode_to_wb_and_lock_list+0xa2/0x750
>>>> fs/fs-writeback.c:281
>>>>  RSP <ffff88006cdaf7d0>
>>>
>>> Man, that's a beautiful trace w/ decoding of inline functions.  When
>>> did we start doing that?  Is there a specific config option for this?
>>
>> Thanks! :)
>> I use this script for symbolization:
>> https://github.com/google/sanitizers/blob/master/address-sanitizer/tools/kasan_symbolize.py
>
> BTW, it would be nice to have that script in kernel tree, instead of
> scripts/decode_stacktrace.sh which
> is far less advanced.


I am all for it!
We have 2 minor, unresolved bugs in the script:
https://github.com/google/sanitizers/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+kasan_symbolize
It would be good to resolve them before submitting it to kernel tree.
But I am not particularly experienced in Python. +Andrey Konovalov
will be able to do it in autumn. If anybody is willing to take it
earlier, you are welcome (please drop a note to
https://github.com/google/sanitizers/issues/674 to coordinate
efforts).


>> It invokes addr2line to provide file:line info, adds inline frames,
>> strips ? frames (are they ever useful?) and strips timestamps.
>> You just need to pipe a report through it. It assumes that vmlinux is
>> in the current dir, but you can override it with --linux flag.
>>
>> It can also insert actual source lines into a report (amount of
>> context is controlled with flags), for example:
>>
>>
>> Call Trace:
>>  [<     inline     >] khugepaged_scan_pmd include/linux/uaccess.h:9
>>       8 {
>>       9         current->pagefault_disabled++;
>>      10 }
>>  [<     inline     >] khugepaged_scan_mm_slot mm/huge_memory.c:2716
>>    2715                                   hend);
>>    2716                         ret = khugepaged_scan_pmd(mm, vma,
>>    2717
>> khugepaged_scan.address,
>>  [<     inline     >] khugepaged_do_scan mm/huge_memory.c:2796
>>    2795                     pass_through_head < 2)
>>    2796                         progress +=
>> khugepaged_scan_mm_slot(pages - progress,
>>    2797                                                             &hpage);
>>  [<ffffffff81790b33>] khugepaged+0x993/0x48e0 mm/huge_memory.c:2831
>>    2830         while (!kthread_should_stop()) {
>>    2831                 khugepaged_do_scan();
>>    2832                 khugepaged_wait_work();
>>  [<ffffffff813c195f>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
>>    1302                         add_wait_queue(k->waitq, &wait);
>>    1303                         __set_current_state(TASK_INTERRUPTIBLE);
>>    1304                 }
>>  [<ffffffff866d1b2f>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:405
>>     404         SWAPGS
>>     405         jmp        restore_regs_and_iret
>>     406 END(ret_from_fork)