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

[Aveline Noir]

Hi SJ,

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

Sorry about that. I'll avoid top-posting from now on : (

> 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?

I've been trying to understand DAMON in more depth with help from
an LLM, not deliberately hunting for bugs. It spotted a few possible
problems as we went through the code. After checking the code and
reproducing them in QEMU, I thought they were worth reporting.
If that wasn't the right way to go about it, please let me know :)

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

That's probably not something normal users would do. The test
deliberately called the update after monitoring stopped and found
that the failed request cleared the old snapshot. It looked
unexpected, so I reported it to ask whether that's intended.

> Is this an answer to my bisection question?

No, that wasn't a `git bisect` run. The suspect commit,
`66178e4ec30a`, came from code review. I tested it and its
parent `cce0b334c310` with the same setup. The parent kept
the snapshot, but the newer commit cleared it.

Thx for your time, and sorry if I've caused any trouble:(

Best,
Aveline