[DRBD-user] umount hang on DRBD 9 client node

David Lee live4thee at gmail.com
Wed Apr 19 17:32:07 CEST 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hi, list

When I umount a DRBD device used by a DRBD client, the 'umount' program
hang, and I got the following call trace:

```
[28076.944996] XFS (drbd100): Unmounting Filesystem
[28198.933553] drbd web: State change failed: Device is held open by someone
[28198.935451] drbd web: Failed: role( Primary -> Secondary )
[28200.828646] INFO: task umount:21558 blocked for more than 120 seconds.
[28200.830496] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[28200.831238] umount          D ffff8801379fc890     0 21558  21271
0x00000084
[28200.831253]  ffff8800a164fd90 0000000000000082 ffff880136345c00
ffff8800a164ffd8
[28200.831282]  ffff8800a164ffd8 ffff8800a164ffd8 ffff880136345c00
ffff8801379fc880
[28200.831284]  ffff8800a1337d10 ffff8801379fc8c0 ffff8801379fc8e8
ffff8801379fc890
[28200.831289] Call Trace:
[28200.831321]  [<ffffffff8163a909>] schedule+0x29/0x70
[28200.831516]  [<ffffffffa023fc41>] xfs_ail_push_all_sync+0xc1/0x110 [xfs]
[28200.831554]  [<ffffffff810a6ae0>] ? wake_up_atomic_t+0x30/0x30
[28200.831572]  [<ffffffffa022ab08>] xfs_unmountfs+0x68/0x190 [xfs]
[28200.831584]  [<ffffffffa022b5eb>] ? xfs_mru_cache_destroy+0x6b/0x90 [xfs]
[28200.831597]  [<ffffffffa022d9c2>] xfs_fs_put_super+0x32/0x90 [xfs]
[28200.831621]  [<ffffffff811e0ab6>] generic_shutdown_super+0x56/0xe0
[28200.831623]  [<ffffffff811e0f07>] kill_block_super+0x27/0x70
[28200.831625]  [<ffffffff811e1249>] deactivate_locked_super+0x49/0x60
[28200.831627]  [<ffffffff811e1846>] deactivate_super+0x46/0x60
[28200.831632]  [<ffffffff811fe785>] mntput_no_expire+0xc5/0x120
[28200.831635]  [<ffffffff811ff8bf>] SyS_umount+0x9f/0x3c0
[28200.831642]  [<ffffffff81645909>] system_call_fastpath+0x16/0x1b
[28320.831678] INFO: task umount:21558 blocked for more than 120 seconds.
[28320.833583] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[28320.834275] umount          D ffff8801379fc890     0 21558  21271
0x00000084
[28320.834286]  ffff8800a164fd90 0000000000000082 ffff880136345c00
ffff8800a164ffd8
[28320.834290]  ffff8800a164ffd8 ffff8800a164ffd8 ffff880136345c00
ffff8801379fc880
[28320.834292]  ffff8800a1337d10 ffff8801379fc8c0 ffff8801379fc8e8
ffff8801379fc890
[28320.834295] Call Trace:
[28320.834349]  [<ffffffff8163a909>] schedule+0x29/0x70
[28320.834653]  [<ffffffffa023fc41>] xfs_ail_push_all_sync+0xc1/0x110 [xfs]
[28320.834688]  [<ffffffff810a6ae0>] ? wake_up_atomic_t+0x30/0x30
[28320.834708]  [<ffffffffa022ab08>] xfs_unmountfs+0x68/0x190 [xfs]
[28320.834724]  [<ffffffffa022b5eb>] ? xfs_mru_cache_destroy+0x6b/0x90 [xfs]
[28320.834752]  [<ffffffffa022d9c2>] xfs_fs_put_super+0x32/0x90 [xfs]
[28320.834771]  [<ffffffff811e0ab6>] generic_shutdown_super+0x56/0xe0
[28320.834775]  [<ffffffff811e0f07>] kill_block_super+0x27/0x70
[28320.834780]  [<ffffffff811e1249>] deactivate_locked_super+0x49/0x60
[28320.834783]  [<ffffffff811e1846>] deactivate_super+0x46/0x60
[28320.834791]  [<ffffffff811fe785>] mntput_no_expire+0xc5/0x120
[28320.834795]  [<ffffffff811ff8bf>] SyS_umount+0x9f/0x3c0
[28320.834803]  [<ffffffff81645909>] system_call_fastpath+0x16/0x1
```

Before umount hang, I did the following steps:
1. mount the drbd device at DRBD client (pure client) node;
2. poweroff 2 of the 3 nodes that contains the resource for the DRBD client
above
3. write to a file under the mount point at step 1
4. umount the drbd device at step 1    <= umount hang

My environment:
# cat /etc/centos-release
CentOS Linux release 7.2.1511 (Core)
# rpm -qa | grep drbd
kmod-drbd-9.0.1_3.10.0_327-1.el7.centos.x86_64
drbdmanage-0.99.4-1.noarch
drbd-utils-8.9.11-1.el7.centos.x86_64

The call trace doesn't show anything obviously related to DRBD 9.  But just
in case.

-- 
Thanks,
Li Qun
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