Re: Long running ioctl and pm, which should have higher priority?

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

在 2025/10/17 21:09, Askar Safin 写道:
> Qu Wenruo <quwenruo.btrfs@gmx.com>:
>> But there is a question concerning me, which should have the higher
>> priority? The long running ioctl or pm?
> 
> Of course, pm.
> 
> I have a huge btrfs fs on a laptop.
> 
> I don't want scrub to prevent suspend, even if that suspend is happening
> automatically.
> 
>> Furthermore the interruption may be indistinguishable between pm and
>> real user signals (SIGINT etc).
> 
> If we interrupted because of signal, ioctl should return EINTR. This is
> what all other syscalls do.
> 
> If we were cancelled, we should return ECANCELED.
> 
> If we interrupted because of process freeze or fs freeze, then... I
> don't know what we should do in this case, but definitely not ECANCELED
> (because we are not cancelled). EINTR will go, or maybe something else
> (EAGAIN?).
> 
> Then, userspace program "btrfs scrub" can resume process if it
> got EINTR. (But this is totally unimportant for me.)

The problem is, dev-replace can not be resumed, but start again from the 
very beginning.
As the interrupted dev-replace will remove the to-be-added device.

Scrub it self is more or less fine, just need some extra parameters to 
tell scrub to start from certain bytenr.

Thanks,
Qu

> 
> Also, please CC me when sending any emails about this scrub/trim bug.
>