Re: 6.17rc5: btrfs scrub, Freezing user space processes failed

["Chris Murphy" <lists@colorremedies.com>]

On Mon, Sep 15, 2025, at 7:37 PM, Qu Wenruo wrote:
> 在 2025/9/16 08:46, Chris Murphy 写道:
>> The storage stack may be relevant: USB flash drive -> dm-crypt -> Btrfs
>
> And for your original report of no response, the problem is since btrfs 
> is blocking the suspension, there should be no extra reason why the 
> system hangs.
>
> Unless there are other corner cases like the USB device is powered off.

I am able to successfully sleep the laptop with the same USB stick inserted and file system mounted, if a scrub is not occurring.


> If you can reproduce the bug, please catch the dying message using 
> something like netconsole.

Difficult. No wired ethernet for the two computers I have available. And previously, trying  to get netconsole to work with WiFi defeated me.


> Yes, that's already a known problem and both David and I were working on 
> this in the past:
>
> https://lore.kernel.org/linux-btrfs/9606fae20bff6c1fbe14dc7b067f3b333c2a955b.1751847905.git.wqu@suse.com/
>
> https://lore.kernel.org/linux-btrfs/20250708132540.28285-1-dsterba@suse.com/
>
>
> My solution is to cancel scrub which is the simplest solution.
> David's solution is pause scrub/balance using extra callbacks and a more 
> complex mechanism.

They need to become aware the scrub/balance was interrupted or cancelled. In any case, they have to manually intervene. So I'm not sure there's a big advantage for pause over cancel.

Also, for read-write scrub, is it appropriate for the /var/lib/btrfs tracking file information to be located in e.g. dev tree on the device being scrubbed or balanced?



-- 
Chris Murphy