Re: [BUG] DAMON sysfs: failed update clears tried_regions snapshot

[SJ Park <sj@kernel.org>]

Hi Aveline,


Please do not "top-post" [1].

On Thu, 15 Oct 2026 10:17:05 -0500 Aveline Noir <jm5905938@gmail.com> wrote:

> Hi SJ,
> 
> I haven't seen this affect a real workload. I found it while testing
> the DAMON sysfs interface.

You shared 4 bug reports in very short time.  Three of those are from 32 bit.
Could you disclose the purpose of the testing and how you are doing the
testing, finding bugs, and reporting those?

> 
> If a tool tries to refresh after monitoring stops, the failed request
> can delete the last snapshot. The tool then has no previous result to
> fall back to.

Why would the tool tries to refresh the regions after the monitoring is
stopped?

> 
> I built and tested 66178e4ec30a and its parent cce0b334c310 with the
> same config and reproducer. In three runs each, the parent kept the
> 4 MiB snapshot after rejecting the refresh; 66178e4ec30a cleared it.
> Both returned -EINVAL.

Is this an answer to my bisection question?

[1] https://subspace.kernel.org/etiquette.html#do-not-top-post-when-replying


Thanks,
SJ

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