linux-kernel - Re: INFO: task hung in grab

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Date:   Wed, 18 Jul 2018 13:02:36 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     syzbot <syzbot+f425456ea8aa16b40d20@...kaller.appspotmail.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: INFO: task hung in grab_super

On Wed, Jul 18, 2018 at 12:49 PM, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> Dmitry,
>
> this is yet another example of stalling inside __bread_gfp().
>
> Can you find all reports where NMI backtrace contains __bread_gfp ?
>
> I need to wget all reports if I try to do that on my side.
> If you can locally grep on your side, it will be nice.


No, I don't have grep. But here are some of the matches:

https://groups.google.com/forum/#!searchin/syzkaller-bugs/__bread_gfp%7Csort:date
https://groups.google.com/forum/#!searchin/syzkaller-upstream-moderation/__bread_gfp%7Csort:date



> On 2018/07/18 19:38, syzbot wrote:
>> CPU: 1 PID: 19991 Comm: syz-executor1 Not tainted 4.18.0-rc5+ #152
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>> RIP: 0010:__lock_is_held+0x76/0x140 kernel/locking/lockdep.c:3741
>> Code: 00 00 4c 8b 6d c8 4d 8d b4 24 38 08 00 00 45 31 ff 48 b8 00 00 00 00 00 fc ff df 49 c1 ed 03 49 01 c5 41 8b 84 24 30 08 00 00 <85> c0 7f 24 e9 85 00 00 00 41 0f b6 45 00 41 83 c7 01 84 c0 74 08
>> RSP: 0018:ffff88018ea3eed8 EFLAGS: 00000086
>> RAX: 0000000000000001 RBX: 0000000000000286 RCX: ffffc9000443f000
>> RDX: 1ffff10031c245de RSI: 00000000ffffffff RDI: ffffffff88f925e0
>> RBP: ffff88018ea3ef18 R08: ffff88018e1226c0 R09: ffffed003b5e46d6
>> R10: 0000000000000003 R11: 0000000000000001 R12: ffff88018e1226c0
>> R13: ffffed0031c245de R14: ffff88018e122ef8 R15: 0000000000000000
>> FS:  00007f243a415700(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: ffffffffff600400 CR3: 00000001d8749000 CR4: 00000000001406e0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>>  lock_is_held_type+0x121/0x210 kernel/locking/lockdep.c:3962
>>  lock_is_held include/linux/lockdep.h:344 [inline]
>>  ___might_sleep+0x295/0x330 kernel/sched/core.c:6152
>>  __might_sleep+0x95/0x190 kernel/sched/core.c:6140
>>  lock_page include/linux/pagemap.h:481 [inline]
>>  pagecache_get_page+0x787/0xe40 mm/filemap.c:1554
>>  find_or_create_page include/linux/pagemap.h:322 [inline]
>>  grow_dev_page fs/buffer.c:940 [inline]
>>  grow_buffers fs/buffer.c:1009 [inline]
>>  __getblk_slow fs/buffer.c:1036 [inline]
>>  __getblk_gfp+0x3bb/0xb10 fs/buffer.c:1313
>>  __bread_gfp+0x2d/0x310 fs/buffer.c:1347
>>  sb_bread_unmovable include/linux/buffer_head.h:313 [inline]
>>  ext4_fill_super+0x6de/0xda80 fs/ext4/super.c:3541
>>  mount_bdev+0x30c/0x3e0 fs/super.c:1174
>>  ext4_mount+0x34/0x40 fs/ext4/super.c:5844
>>  mount_fs+0xae/0x328 fs/super.c:1277
>>  vfs_kern_mount.part.34+0xdc/0x4e0 fs/namespace.c:1037
>>  vfs_kern_mount fs/namespace.c:1027 [inline]
>>  do_new_mount fs/namespace.c:2518 [inline]
>>  do_mount+0x581/0x30e0 fs/namespace.c:2848
>>  ksys_mount+0x12d/0x140 fs/namespace.c:3064
>>  __do_sys_mount fs/namespace.c:3078 [inline]
>>  __se_sys_mount fs/namespace.c:3075 [inline]
>>  __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
>>  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>>  entry_SYSCALL_64_after_hwframe+0x49/0xbe