[Ocfs2-devel] [Ocfs2-dev] BUG: deadlock with umount and ocfs2 workqueue triggered by ocfs2rec thread

[Joseph Qi]

Hi Changkuo,

You said s_umount was acquired by umount and ocfs2rec was blocked when
acquiring it. But you didn't describe why umount was blocked.

Thanks,
Joseph

On 18/1/12 11:43, Shichangkuo wrote:
> Hi all,
> 　　Now we are testing ocfs2 with 4.14 kernel, and we finding a deadlock with umount and ocfs2 workqueue triggered by ocfs2rec thread. The stack as follows:
> journal recovery work:
> [<ffffffff8a8c0694>] call_rwsem_down_read_failed+0x14/0x30
> [<ffffffffc0d5d652>] ocfs2_finish_quota_recovery+0x62/0x450 [ocfs2]
> [<ffffffffc0d21221>] ocfs2_complete_recovery+0xc1/0x440 [ocfs2]
> [<ffffffff8a09a1f0>] process_one_work+0x130/0x350
> [<ffffffff8a09a946>] worker_thread+0x46/0x3b0
> [<ffffffff8a0a0e51>] kthread+0x101/0x140
> [<ffffffff8aa002ff>] ret_from_fork+0x1f/0x30
> [<ffffffffffffffff>] 0xffffffffffffffff
> 
> /bin/umount:
> [<ffffffff8a099b24>] flush_workqueue+0x104/0x3e0
> [<ffffffffc0cf18db>] ocfs2_truncate_log_shutdown+0x3b/0xc0 [ocfs2]
> [<ffffffffc0d4fd6c>] ocfs2_dismount_volume+0x8c/0x3d0 [ocfs2]
> [<ffffffffc0d500e1>] ocfs2_put_super+0x31/0xa0 [ocfs2]
> [<ffffffff8a2445bd>] generic_shutdown_super+0x6d/0x120
> [<ffffffff8a24469d>] kill_block_super+0x2d/0x60
> [<ffffffff8a244e71>] deactivate_locked_super+0x51/0x90
> [<ffffffff8a263a1b>] cleanup_mnt+0x3b/0x70
> [<ffffffff8a09e9c6>] task_work_run+0x86/0xa0
> [<ffffffff8a003d70>] exit_to_usermode_loop+0x6d/0xa9
> [<ffffffff8a003a2d>] do_syscall_64+0x11d/0x130
> [<ffffffff8aa00113>] entry_SYSCALL64_slow_path+0x25/0x25
> [<ffffffffffffffff>] 0xffffffffffffffff
> 　　
> Function ocfs2_finish_quota_recovery try to get sb->s_umount, which was already locked by umount thread, then get a deadlock.
> This issue was introduced by c3b004460d77bf3f980d877be539016f2df4df12 and 5f530de63cfc6ca8571cbdf58af63fb166cc6517.
> I think we cannot use :: s_umount, but the mutex ::dqonoff_mutex was already removed.
> Shall we add a new mutex?
> 
> Thanks
> Changkuo
> -------------------------------------------------------------------------------------------------------------------------------------
> 本邮件及其附件含有新华三技术有限公司的保密信息，仅限于发送给上面地址中列出
> 的个人或群组。禁止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、
> 或散发）本邮件中的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本
> 邮件！
> This e-mail and its attachments contain confidential information from New H3C, which is
> intended only for the person or entity whose address is listed above. Any use of the
> information contained herein in any way (including, but not limited to, total or partial
> disclosure, reproduction, or dissemination) by persons other than the intended
> recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender
> by phone or email immediately and delete it!
> _______________________________________________
> Ocfs2-devel mailing list
> Ocfs2-devel at oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>