Re: Pausing md check hangs

[Song Liu <song@kernel.org>]

On Mon, Jan 27, 2020 at 5:44 AM Georgi Nikolov <gnikolov@icdsoft.com> wrote:
>
> Hi,
>
> I posted a kernel bug about this a month ago but it did not receive any
> attention: https://bugzilla.kernel.org/show_bug.cgi?id=205929
> Here is a copy of the bug report and I hope that this is the correct
> place to discuss this:
>
> I have a Supermicro server with 10 md raid6 arrays each consisting of 8
> SATA drives. SATA drives are Hitachi/HGST Ultrastar 7K4000 8T.
> When i try to pause array check with "echo idle >
> "/sys/block/<md_dev>/md/sync_action" it randomly hangs at different md
> device.
> Process "mdX_raid6" is at 100% cpu usage. cat
> /sys/block/mdX/md/journal_mode hungs forever.
>
> Here is the state at the moment of crash for one of the md devices:
>
> root@supermicro:/sys/block/mdX/md# find -mindepth 1 -maxdepth 1 -type
> f|sort|grep -v journal_mode|xargs -r egrep .
> ./array_size:default
> ./array_state:write-pending
> grep: ./bitmap_set_bits: Permission denied
> ./chunk_size:524288
> ./component_size:7813895168
> ./consistency_policy:resync
> ./degraded:0
> ./group_thread_cnt:4
> ./last_sync_action:check
> ./layout:2
> ./level:raid6
> ./max_read_errors:20
> ./metadata_version:1.2
> ./mismatch_cnt:0
> grep: ./new_dev: Permission denied
> ./preread_bypass_threshold:1
> ./raid_disks:8
> ./reshape_direction:forwards
> ./reshape_position:none
> ./resync_start:none
> ./rmw_level:1
> ./safe_mode_delay:0.204
> ./skip_copy:0
> ./stripe_cache_active:13173
> ./stripe_cache_size:8192
> ./suspend_hi:0
> ./suspend_lo:0
> ./sync_action:check
> ./sync_completed:3566405120 / 15627790336
> ./sync_force_parallel:0
> ./sync_max:max
> ./sync_min:1821385984
> ./sync_speed:126
> ./sync_speed_max:1000 (local)
> ./sync_speed_min:1000 (system)
>
> root@supermicro:~# cat /proc/mdstat
> Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5]
> [raid4] [raid10]
> md4 : active raid6 sdaa[2] sdab[3] sdy[0] sdae[6] sdac[4] sdad[5]
> sdaf[7] sdz[1]
>        46883371008 blocks super 1.2 level 6, 512k chunk, algorithm 2
> [8/8] [UUUUUUUU]
>        [====>................]  check = 22.8% (1784112640/7813895168)
> finish=20571.7min speed=4884K/sec

Thanks for the report.

Could you please confirm the kernel is 4.19.67-2+deb10u2 amd64?
Also, have you tried different kernels?

Song