[linux-lvm] Unexptected filesytem unmount with thin provision and autoextend disabled - lvmetad crashed?

[Gionatan Danti]

> Well yeah - ATM we rather take 'early' action and try to stop any user
> on overfill thin-pool.
>

It is a very reasonable standing

>
>
> Basically whenever  'lvresize' failed - dmeventd plugin now tries
> to unconditionally umount any associated thin-volume with
> thin-pool above threshold.
>
>
>
> For now  -  plugin   'calls'  the tool - lvresize --use-policies.
> If this tool FAILs for ANY  reason ->  umount will happen.
>
> I'll probably put in 'extra' test that 'umount' happens
> with  >=95% values only.
>
> dmeventd  itself has no idea if there is configure 100 or less - it's
> the lvresize to see it - so even if you set 100% - and you have enabled
> monitoring  - you will get umount (but no resize)
>
>

Ok, so the "failed to resize" error is also raised when no actual resize 
happens, but the call to the "dummy" lvresize fails. Right?

>
> If you strictly don't care about any tracing of thin-pool fullness,
> disable  monitoring in lvm.conf.
>

While this thin pool should never be overfilled (it has a single, 
slightly smaller volume with no snapshot in place) I would really like 
to leave monitoring enabled, as it can prevent some nasty suprises (eg: 
avoid pool overfilling by a snapshot that is "forgotten" and never removed).

>
>
> Well 'lvmetad' shall not crash, ATM this may kill commands - and further
> stop processing - as we rather 'stop' further usage rather than allowing
> to cause bigger damage.
>
> So if you have unusual system/device setup causing  'lvmetad' crash -
> open BZ,
> and meawhile  set   'use_lvmetad=0' in your lvm.conf till the bug is fixed.
>

My 2 cents are that the last "yum upgrade", which affected the lvm 
tools, needed a system reboot or at least the restart of the lvm-related 
services (dmeventd and lvmetad). The strange thing is that, even if 
lvmetad crashed, it should be restartable via the lvm2-lvmetad.socket 
systemd unit. Is this a wrong expectation?

Thanks.

-- 
Danti Gionatan
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Assyoma S.r.l. - www.assyoma.it
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