linux-kernel - Re: fs: GPF in locked_inode_to_wb_and_lock

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Message-ID: <CACT4Y+bXBZZxksEo_Zx1pRk1zpsb16UjUJY8=RK+2zoqjNj2=A@mail.gmail.com>
Date:	Thu, 21 Apr 2016 10:25:12 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>
Subject: Re: fs: GPF in locked_inode_to_wb_and_lock_list

On Wed, Apr 20, 2016 at 11:14 PM, Tejun Heo <tj@...nel.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
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)