[Xen-devel] blkdev_issue_discard hung

[Olivier Bonvalet <xen.list@xxxxxxxxx>]

Hi,

I have a problem with Xen 4.8.2 (or Linux 4.9.51 as dom0 kernel) :
calls to DISCARD command from the DomU frequently hang.
I also have the problem with Xen 4.8.1 and Linux 4.9 from Debian 9
(stretch) repositories.

Here logs from dom0 :

Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540610] INFO: task 1.xvdo-0:2740 
blocked for more than 120 seconds.
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540667]       Not tainted 4.9-dae-dom0 
#1
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540699] "echo 0 > 
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540752] 1.xvdo-0        D    0  2740   
   2 0x00000000
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540758]  ffff88027c6ac080 
0000000000000000 ffff880285617e00 ffff88027ff4a280
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540763]  ffff88027c762fc0 
ffffc90011cdfbc0 ffffffff8153c720 ffff880279e40600
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540767]  ffff88027c762fc0 
7fffffffffffffff ffff88027c762fc0 00000000007fe000
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540770] Call Trace:
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540783]  [<ffffffff8153c720>] ? 
__schedule+0x190/0x570
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540786]  [<ffffffff8153cb2d>] ? 
schedule+0x2d/0x80
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540793]  [<ffffffff8153fbce>] ? 
schedule_timeout+0x17e/0x2a0
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540799]  [<ffffffff8125a5c5>] ? 
generic_make_request_checks+0x145/0x430
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540804]  [<ffffffff810c2cf6>] ? 
ktime_get+0x36/0xa0
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540808]  [<ffffffff8153c528>] ? 
io_schedule_timeout+0x98/0x100
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540811]  [<ffffffff8153ddb4>] ? 
wait_for_completion_io+0xa4/0x120
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540815]  [<ffffffff81088040>] ? 
wake_up_q+0x70/0x70
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540823]  [<ffffffff81255ca7>] ? 
submit_bio_wait+0x47/0x60
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540826]  [<ffffffff81263fa5>] ?        
0x65/0xa0
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540837]  [<ffffffffa02d9e3e>] ? 
__do_block_io_op+0x3be/0x610 [xen_blkback]
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540841]  [<ffffffffa02da521>] ? 
xen_blkif_schedule+0x101/0x6f0 [xen_blkback]
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540847]  [<ffffffff8109ca10>] ? 
wake_atomic_t_function+0x50/0x50
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540850]  [<ffffffffa02da420>] ? 
xen_blkif_be_int+0x30/0x30 [xen_blkback]
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540854]  [<ffffffff81080a52>] ? 
kthread+0xc2/0xe0
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540856]  [<ffffffff81080990>] ? 
kthread_create_on_node+0x40/0x40
Sep 25 22:32:44 hyp04-sbg kernel: [ 7468.540859]  [<ffffffff81540e05>] ? 
ret_from_fork+0x25/0x30

Any ideas about what's happening, and how to fix that ?

Thanks,

Olivier

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