[Xen-devel] Block device hang after migration

[Wei Liu <wei.liu2@xxxxxxxxxx>]

Hi

In the process of upgrading osstest to Stretch, I discovered an issue
with the block device. This happens after a local migration.

[  127.216232] Freezing user space processes ... (elapsed 0.005 seconds) done.
[  127.222143] Freezing remaining freezable tasks ... 
[  147.228913] Freezing of tasks failed after 20.006 seconds (1 tasks refusing 
to freeze, wq_busy=0):
[  147.228935] jbd2/xvda1-8    D    0   143      2 0x00000000
[  147.228964]  ffff880005109000 0000000000000000 ffff88000569e000 
ffff88001f918240
[  147.228984]  ffff88001ea7a000 ffffc9004029bb30 ffffffff816038e3 
ffffc9004029bbe8
[  147.229001]  00ff8800056d1500 ffff88001f918240 0000000000000000 
ffff88000569e000
[  147.229028] Call Trace:
[  147.229274]  [<ffffffff816038e3>] ? __schedule+0x233/0x6d0
[  147.229297]  [<ffffffff81604550>] ? bit_wait+0x50/0x50
[  147.229307]  [<ffffffff81603db2>] ? schedule+0x32/0x80
[  147.229318]  [<ffffffff8160711e>] ? schedule_timeout+0x1de/0x350
[  147.229345]  [<ffffffff8101b601>] ? xen_clocksource_get_cycles+0x11/0x20
[  147.229363]  [<ffffffff810ec47b>] ? ktime_get+0x3b/0xb0
[  147.229378]  [<ffffffff81604550>] ? bit_wait+0x50/0x50
[  147.229389]  [<ffffffff8160364d>] ? io_schedule_timeout+0x9d/0x100
[  147.229401]  [<ffffffff810b8ab7>] ? prepare_to_wait+0x57/0x80
[  147.229417]  [<ffffffff81604567>] ? bit_wait_io+0x17/0x60
[  147.229427]  [<ffffffff81604133>] ? __wait_on_bit+0x53/0x80
[  147.229442]  [<ffffffff81604550>] ? bit_wait+0x50/0x50
[  147.229457]  [<ffffffff8160428e>] ? out_of_line_wait_on_bit+0x7e/0xa0
[  147.229469]  [<ffffffff810b8f20>] ? wake_atomic_t_function+0x60/0x60
[  147.229563]  [<ffffffffc007cde2>] ? 
jbd2_journal_commit_transaction+0xdd2/0x17a0 [jbd2]
[  147.229589]  [<ffffffff8109da1d>] ? finish_task_switch+0x7d/0x1f0
[  147.229612]  [<ffffffffc0081bc2>] ? kjournald2+0xc2/0x260 [jbd2]
[  147.229624]  [<ffffffff810b8e80>] ? prepare_to_wait_event+0xf0/0xf0
[  147.229643]  [<ffffffffc0081b00>] ? commit_timeout+0x10/0x10 [jbd2]
[  147.229656]  [<ffffffff81096697>] ? kthread+0xd7/0xf0
[  147.229667]  [<ffffffff810965c0>] ? kthread_park+0x60/0x60
[  147.229684]  [<ffffffff81608835>] ? ret_from_fork+0x25/0x30
[  147.229708] Restarting kernel threads ... done.
[  147.230496] xen:manage: do_suspend: freeze kernel threads failed -16
[  147.230508] Restarting tasks ... done.
[  238.484918] 

http://logs.test-lab.xenproject.org/osstest/logs/114709/test-amd64-amd64-xl-qcow2/fiano1---var-log-xen-console-guest-debian.stretch.guest.osstest--incoming.log

And this seems to be the same issue Olivier Bonvale reported in "[Xen-devel]
task btrfs-transacti:651 blocked for more than 120 seconds".

The guest in osstest uses ext4, with only one or two vbds. Kernel is Debian's
stock kernel (4.9).

The guest configuration can be found at:

http://logs.test-lab.xenproject.org/osstest/logs/114709/test-amd64-amd64-xl-qcow2/info.html

Wei.

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