On Sat, Jul 30, 2016 at 02:10:32PM -0600, Chris Murphy wrote:
On Sat, Jul 30, 2016 at 10:44 AM, Chris Adams
<linux(a)cmadams.net> wrote:
> Once upon a time, Chris Murphy <lists(a)colorremedies.com> said:
>> On Fri, Jul 29, 2016 at 2:36 PM, Chris Adams <linux(a)cmadams.net> wrote:
>> > The actual work of pvmove is not done by the command you run; that sets
>> > it up and it is run in the background (by a kernel thread). All the
>> > command you run does then is periodically check and print a percentage
>> > done.
>>
>> It's the same with btrfs balance and scrub. It may be the operation
>> completes by kernel code, but with user space detached from the kill,
>> the status/statistics are lost.
>
> I don't know about btrfs, but with LVM, nothing is lost. You can run
> "pvmove" at any time to continue to show the status.
I see the same behavior. I'm not sure what the user space tool
reattaches to, something in sysfs or lvmetad?
> And we're talking about KillUserProcesses; logging out _already_ killed
> the pvmove command. Nothing has changed.
Guess we'll see what btrfs upstream thinks about it, but the idea that
Btrfs users are going to know their scrubs fail due to this feature is
flawed. There's zero indication why the process dies, and there's no
way to get more information in the journal to hint at why it dies.
Plus it's inconsistent. Neither btrfs balance nor replace have this
problem, those processes continue to run with status D and R until
they complete.
If KillUserProcessess is on, systemd logs when cleanup happens (in v231+).
It is up to admin to connect the dots. Personally I'm using following
unit:
---
[Unit]
Description=btrfs scrub of %I
[Service]
ExecStart=/usr/sbin/btrfs scrub start -B -d %I
ExecReload=/usr/sbin/btrfs scrub status %I
ExecStop=-/usr/sbin/btrfs scrub cancel %I
IOSchedulingClass=idle
BlockIOWeight=128
PrivateDevices=yes
PrivateNetwork=yes
PrivateTmp=yes
---
Integrates nicely with timers.
Why do you require systemd v230? KillUserProcess exists for
5 years already, it should work the same with all systemd.
Has anything changed in 230?
--
Tomasz Torcz Morality must always be based on practicality.
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