On 3/22/22 00:44, David Teigland wrote:
On Mon, Mar 21, 2022 at 04:57:09PM +0800, heming.zhao@xxxxxxxx wrote:
```
Mar 10 10:27:54 Mobile-PC systemd[1]: Stopped target Local File Systems.
Mar 10 10:27:55 Mobile-PC systemd[1]: Reached target Local File Systems.
Mar 10 10:27:55 Mobile-PC lvm[658]: Udev database has incomplete information about device /dev/nvme0n1.
Mar 10 10:27:55 Mobile-PC lvm[658]: /dev/nvme0n1: Failed to get external handle [udev].
Mar 10 10:27:55 Mobile-PC lvm[658]: Udev database has incomplete information about device /dev/sda.
Mar 10 10:27:55 Mobile-PC lvm[658]: /dev/sda: Failed to get external handle [udev].
```
Since vgchange --monitor runs during startup, it should also override any
udev settings to disable them, like pvscan does:
init_obtain_device_list_from_udev(0);
init_external_device_info_source(DEV_EXT_NONE);
(Those are the default settings we use, so we don't see this.)
you mind me, I forgot SUSE chose to use udev by default.
So this is a SUSE special issue.
In my understand, lvm2-monitor.service does the "clean up" job, which will complete the
monitor job for thin/mirror/others LVs, which was created during initrd phase. (because
lvm_scan doesn't have ability to start monitoring.)
on current lvm2-monitor.service, the dependency asks this service start as early as possible:
```
After=dm-event.socket dm-event.service
```
It makes monitor service start too early, and triggers libudev not ready issue.
To fix above issue, we find a workaround:
```
- After=dm-event.socket dm-event.service
+ After=dm-event.socket dm-event.service sysinit.target
```
Yes, I think starting it later would be better. I don't know enough about
these systemd targets to comment on how well that change would work. I've
not given much attention to lvm2-monitor, but I've also wished it would
start later>
And maybe there is another workaround (not verify):
```
-ExecStart=@SBINDIR@/lvm vgchange --monitor y
+ExecStart=@SBINDIR@/lvm vgchange --config 'devices { external_device_info_source="none" \
obtain_device_list_from_udev=0}' --monitor y
```
Let's patch vgchange monitor as mentioned above.
Dave
I inclined to use the "--config" option to avoid booting warning.
(or write additional codes for vgchange "monitor_ARG")
I have two reasons:
1>
Martin & I also found it is a difficult to find the best time to start lvm2-monitor.service
So modification "After=" dependency will still failed with some cases.
2>
the lvm2-monitor.service helps to finish monitoring job for lvm_scan. So it's not necessary
to ask this service to handle the VG/LV which starting after switch rootfs. (These VG/LV
should be monitored by "pvscan --cache".)
So starting lvm2-monitor.service as early as possible is accepted.
Thanks,
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