Re: [REGRESSION] 6.7.1: md: raid5 hang and unresponsive system; successfully bisected

[Blazej Kucman <blazej.kucman@linux.intel.com>]

Hi,

On Fri, 26 Jan 2024 08:46:10 -0700
Dan Moulding <dan@danm.net> wrote: 
> 
> That's a good suggestion, so I switched it to use XFS. It can still
> reproduce the hang. Sounds like this is probably a different problem
> than the known ext4 one.
> 

Our daily tests directed at mdadm/md also detected a problem with
identical symptoms as described in the thread.

Issue detected with IMSM metadata but it also reproduces with native
metadata.
NVMe disks under VMD controller were used.

Scenario:
1. Create raid10:
mdadm --create /dev/md/r10d4s128-15_A --level=10 --chunk=128
--raid-devices=4 /dev/nvme6n1 /dev/nvme2n1 /dev/nvme3n1 /dev/nvme0n1
--size=7864320 --run
2. Create FS
mkfs.ext4 /dev/md/r10d4s128-15_A
3. Set faulty one raid member:
mdadm --set-faulty /dev/md/r10d4s128-15_A /dev/nvme3n1
4. Stop raid devies:
mdadm -Ss

Expected result:
The raid stops without kernel hangs and errors.

Actual result:
command "mdadm -Ss" hangs,
hung_task occurs in OS.

[   62.770472] md: resync of RAID array md127
[  140.893329] md: md127: resync done.
[  204.100490] md/raid10:md127: Disk failure on nvme3n1, disabling
device. md/raid10:md127: Operation continuing on 3 devices.
[  244.625393] INFO: task kworker/48:1:755 blocked for more than 30
seconds. [  244.632294]       Tainted: G S
6.8.0-rc1-20240129.intel.13479453+ #1 [  244.640157] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message. [
244.648105] task:kworker/48:1    state:D stack:14592 pid:755   tgid:755
  ppid:2      flags:0x00004000 [  244.657552] Workqueue: md_misc
md_start_sync [md_mod] [  244.662688] Call Trace: [  244.665176]  <TASK>
[  244.667316]  __schedule+0x2f0/0x9c0
[  244.670868]  ? sched_clock+0x10/0x20
[  244.674510]  schedule+0x28/0x90
[  244.677703]  mddev_suspend+0x11d/0x1e0 [md_mod]
[  244.682313]  ? __update_idle_core+0x29/0xc0
[  244.686574]  ? swake_up_all+0xe0/0xe0
[  244.690302]  md_start_sync+0x3c/0x280 [md_mod]
[  244.694825]  process_scheduled_works+0x87/0x320
[  244.699427]  worker_thread+0x147/0x2a0
[  244.703237]  ? rescuer_thread+0x2d0/0x2d0
[  244.707313]  kthread+0xe5/0x120
[  244.710504]  ? kthread_complete_and_exit+0x20/0x20
[  244.715370]  ret_from_fork+0x31/0x40
[  244.719007]  ? kthread_complete_and_exit+0x20/0x20
[  244.723879]  ret_from_fork_asm+0x11/0x20
[  244.727872]  </TASK>
[  244.730117] INFO: task mdadm:8457 blocked for more than 30 seconds.
[  244.736486]       Tainted: G S
6.8.0-rc1-20240129.intel.13479453+ #1 [  244.744345] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message. [
244.752293] task:mdadm           state:D stack:13512 pid:8457
tgid:8457  ppid:8276   flags:0x00000000 [  244.761736] Call Trace: [
244.764241]  <TASK> [  244.766389]  __schedule+0x2f0/0x9c0
[  244.773224]  schedule+0x28/0x90
[  244.779690]  stop_sync_thread+0xfa/0x170 [md_mod]
[  244.787737]  ? swake_up_all+0xe0/0xe0
[  244.794705]  do_md_stop+0x51/0x4c0 [md_mod]
[  244.802166]  md_ioctl+0x59d/0x10a0 [md_mod]
[  244.809567]  blkdev_ioctl+0x1bb/0x270
[  244.816417]  __x64_sys_ioctl+0x7a/0xb0
[  244.823720]  do_syscall_64+0x4e/0x110
[  244.830481]  entry_SYSCALL_64_after_hwframe+0x63/0x6b
[  244.838700] RIP: 0033:0x7f2c540c97cb
[  244.845457] RSP: 002b:00007fff4ad6a8f8 EFLAGS: 00000246 ORIG_RAX:
0000000000000010 [  244.856265] RAX: ffffffffffffffda RBX:
0000000000000003 RCX: 00007f2c540c97cb [  244.866659] RDX:
0000000000000000 RSI: 0000000000000932 RDI: 0000000000000003 [
244.877031] RBP: 0000000000000019 R08: 0000000000200000 R09:
00007fff4ad6a4c5 [  244.887382] R10: 0000000000000000 R11:
0000000000000246 R12: 00007fff4ad6a9c0 [  244.897723] R13:
00007fff4ad6a9a0 R14: 000055724d0990e0 R15: 000055724efaa780 [
244.908018]  </TASK> [  275.345375] INFO: task kworker/48:1:755 blocked
for more than 60 seconds. [  275.355363]       Tainted: G S
    6.8.0-rc1-20240129.intel.13479453+ #1 [  275.366306] "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message. [
275.377334] task:kworker/48:1    state:D stack:14592 pid:755   tgid:755
  ppid:2      flags:0x00004000 [  275.389863] Workqueue: md_misc
md_start_sync [md_mod] [  275.398102] Call Trace: [  275.403673]  <TASK>


Also reproduces with XFS FS, does not reproduce when there is no FS on
RAID.

Repository used for testing:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
Branch: master

Last working build: kernel branch HEAD: acc657692aed ("keys, dns: Fix
size check of V1 server-list header")

I see one merge commit touching md after the above one:
01d550f0fcc0 ("Merge tag 'for-6.8/block-2024-01-08' of
git://git.kernel.dk/linux")

I hope these additional logs will help find the cause.

Thanks,
Blazej