[systemd-devel] Errorneous detection of degraded array

[Andrei Borzenkov]

27.01.2017 22:44, Luke Pyzowski пишет:
...
> Jan 27 11:33:14 lnxnfs01 kernel: md/raid:md0: raid level 6 active with 24 out of 24 devices, algorithm 2
...
> Jan 27 11:33:14 lnxnfs01 kernel: md0: detected capacity change from 0 to 45062020923392
> Jan 27 11:33:14 lnxnfs01 systemd[1]: Found device /dev/disk/by-uuid/2b9114be-3d5a-41d7-8d4b-e5047d223129.
> Jan 27 11:33:14 lnxnfs01 systemd[1]: Started udev Wait for Complete Device Initialization.
> Jan 27 11:33:14 lnxnfs01 systemd[1]: Started Timer to wait for more drives before activating degraded array..
> Jan 27 11:33:14 lnxnfs01 systemd[1]: Starting Timer to wait for more drives before activating degraded array..
...
> 
> ... + 31 seconds from disk initialization, expiration of 30 second timer from mdadm-last-resort at .timer
> 
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Created slice system-mdadm\x2dlast\x2dresort.slice.
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Starting system-mdadm\x2dlast\x2dresort.slice.
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Stopped target Local File Systems.
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Stopping Local File Systems.
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Unmounting Mount /share RAID partition explicitly...
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Starting Activate md array even though degraded...
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Stopped (with error) /dev/md0.
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Started Activate md array even though degraded.
> Jan 27 11:33:45 lnxnfs01 systemd[1]: Unmounted Mount /share RAID partition explicitly.
> 

Here is my educated guess.

Both mdadm-last-resort at .timer and mdadm-last-resort at .service conflict
with MD device:

bor at bor-Latitude-E5450:~/src/systemd$ cat ../mdadm/systemd/
mdadm-grow-continue at .service  mdadm.shutdown
SUSE-mdadm_env.sh
mdadm-last-resort at .service    mdmonitor.service
mdadm-last-resort at .timer      mdmon at .service
bor at bor-Latitude-E5450:~/src/systemd$ cat
../mdadm/systemd/mdadm-last-resort at .timer
[Unit]
Description=Timer to wait for more drives before activating degraded array.
DefaultDependencies=no
Conflicts=sys-devices-virtual-block-%i.device

[Timer]
OnActiveSec=30
bor at bor-Latitude-E5450:~/src/systemd$ cat
../mdadm/systemd/mdadm-last-resort at .service
[Unit]
Description=Activate md array even though degraded
DefaultDependencies=no
Conflicts=sys-devices-virtual-block-%i.device

[Service]
Type=oneshot
ExecStart=BINDIR/mdadm --run /dev/%i

I presume intention is to stop these units when MD device is finally
assembled as complete. This is indeed what happens on my (test) system:

Jan 28 14:18:04 linux-ffk5 kernel: md: bind<vda1>
Jan 28 14:18:04 linux-ffk5 kernel: md: bind<vdb1>
Jan 28 14:18:05 linux-ffk5 kernel: md/raid1:md0: active with 2 out of 2
mirrors
Jan 28 14:18:05 linux-ffk5 kernel: md0: detected capacity change from 0
to 5363466240
Jan 28 14:18:06 linux-ffk5 systemd[1]: mdadm-last-resort at md0.timer:
Installed new job mdadm-last-resort at md0.timer/start as 287
Jan 28 14:18:06 linux-ffk5 systemd[1]: mdadm-last-resort at md0.timer:
Enqueued job mdadm-last-resort at md0.timer/start as 287
Jan 28 14:18:06 linux-ffk5 systemd[1]: dev-ttyS9.device: Changed dead ->
plugged
Jan 28 14:18:07 linux-ffk5 systemd[1]: mdadm-last-resort at md0.timer:
Changed dead -> waiting
Jan 28 14:18:12 linux-ffk5 systemd[1]:
sys-devices-virtual-block-md0.device: Changed dead -> plugged
Jan 28 14:18:12 linux-ffk5 systemd[1]: mdadm-last-resort at md0.timer:
Trying to enqueue job mdadm-last-resort at md0.timer/stop/replace
Jan 28 14:18:12 linux-ffk5 systemd[1]: mdadm-last-resort at md0.timer:
Installed new job mdadm-last-resort at md0.timer/stop as 292
Jan 28 14:18:12 linux-ffk5 systemd[1]: mdadm-last-resort at md0.timer:
Enqueued job mdadm-last-resort at md0.timer/stop as 292
Jan 28 14:18:12 linux-ffk5 systemd[1]: mdadm-last-resort at md0.timer:
Changed waiting -> dead
Jan 28 14:18:12 linux-ffk5 systemd[1]: mdadm-last-resort at md0.timer: Job
mdadm-last-resort at md0.timer/stop finished, result=done
Jan 28 14:18:12 linux-ffk5 systemd[1]: Stopped Timer to wait for more
drives before activating degraded array..
Jan 28 14:19:34 10 systemd[1692]: dev-vda1.device: Changed dead -> plugged
Jan 28 14:19:34 10 systemd[1692]: dev-vdb1.device: Changed dead -> plugged


On your system apparently timer is not stopped when md device appears so
that when later last-resort service runs, it causes attempt to stop md
device (due to conflict) and transitively mount on top of it.

Could you try run with systemd.log_level=debug on kernel command line
and upload journal again. We can only hope that it will not skew timings
enough but it may prove my hypothesis.
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