[Ocfs2-users] umount hung on two hosts

[Robin Lee]

Hi,

In a OCFS2 cluster of XenServer 7.1.1 hosts, we met umount hung on two
different hosts.
The kernel is based on Linux 4.4.27.
The cluster has 9 hosts and 8 OCFS2 filesystems.
Though umount is hanging, the mountpoint entry already disappeared in
/proc/mounts.
Despite this issue, the OCFS2 filesystems are working well.

the first umount stack: (by cat /proc/PID/stack)
[<ffffffff810d05cd>] msleep+0x2d/0x40
[<ffffffffa0620409>] dlmunlock+0x2c9/0x490 [ocfs2_dlm]
[<ffffffffa04461a5>] o2cb_dlm_unlock+0x35/0x50 [ocfs2_stack_o2cb]
[<ffffffffa0574120>] ocfs2_dlm_unlock+0x20/0x30 [ocfs2_stackglue]
[<ffffffffa06531e0>] ocfs2_drop_lock.isra.20+0x250/0x370 [ocfs2]
[<ffffffffa0654a36>] ocfs2_drop_inode_locks+0xa6/0x180 [ocfs2]
[<ffffffffa0661d13>] ocfs2_clear_inode+0x343/0x6d0 [ocfs2]
[<ffffffffa0663616>] ocfs2_evict_inode+0x526/0x5d0 [ocfs2]
[<ffffffff811cd816>] evict+0xb6/0x170
[<ffffffff811ce495>] iput+0x1c5/0x1f0
[<ffffffffa068cbd0>] ocfs2_release_system_inodes+0x90/0xd0 [ocfs2]
[<ffffffffa068dfad>] ocfs2_dismount_volume+0x17d/0x390 [ocfs2]
[<ffffffffa068e210>] ocfs2_put_super+0x50/0x80 [ocfs2]
[<ffffffff811b6e6f>] generic_shutdown_super+0x6f/0x100
[<ffffffff811b6f87>] kill_block_super+0x27/0x70
[<ffffffff811b68bb>] deactivate_locked_super+0x3b/0x70
[<ffffffff811b6949>] deactivate_super+0x59/0x60
[<ffffffff811d18a8>] cleanup_mnt+0x58/0x80
[<ffffffff811d1922>] __cleanup_mnt+0x12/0x20
[<ffffffff8108c2ad>] task_work_run+0x7d/0xa0
[<ffffffff8106d2b9>] exit_to_usermode_loop+0x73/0x98
[<ffffffff81003961>] syscall_return_slowpath+0x41/0x50
[<ffffffff815a0acc>] int_ret_from_sys_call+0x25/0x8f
[<ffffffffffffffff>] 0xffffffffffffffff

the second umount stack:
[<ffffffff81087398>] flush_workqueue+0x1c8/0x520
[<ffffffffa06700c9>] ocfs2_shutdown_local_alloc+0x39/0x410 [ocfs2]
[<ffffffffa0692edd>] ocfs2_dismount_volume+0xad/0x390 [ocfs2]
[<ffffffffa0693210>] ocfs2_put_super+0x50/0x80 [ocfs2]
[<ffffffff811b6e6f>] generic_shutdown_super+0x6f/0x100
[<ffffffff811b6f87>] kill_block_super+0x27/0x70
[<ffffffff811b68bb>] deactivate_locked_super+0x3b/0x70
[<ffffffff811b6949>] deactivate_super+0x59/0x60
[<ffffffff811d18a8>] cleanup_mnt+0x58/0x80
[<ffffffff811d1922>] __cleanup_mnt+0x12/0x20
[<ffffffff8108c2ad>] task_work_run+0x7d/0xa0
[<ffffffff8106d2b9>] exit_to_usermode_loop+0x73/0x98
[<ffffffff81003961>] syscall_return_slowpath+0x41/0x50
[<ffffffff815a0acc>] int_ret_from_sys_call+0x25/0x8f
[<ffffffffffffffff>] 0xffffffffffffffff

-robin