Re: [PATCH v5 10/19] selftests/mm: add khugepaged completion barrier helper

[Baolin Wang]

On 9/8/26 8:50 PM, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>
>
> A khugepaged test has to tell "not collapsed" from "not scanned yet", and
> nothing in the selftests can.  wait_for_scan() in khugepaged.c comes
> closest: it polls full_scans until the counter has advanced by two, since
> the pass in progress may already have passed the test's mm.  But it only
> returns in time if scan_sleep_millisecs happens to be short, and it is
> private to that one test.
>
> Add khugepaged_full_pass() to hugepage_settings, built on the same
> advance-by-two wait but driven through sysfs: a store to
> scan_sleep_millisecs wakes the daemon, so the barrier completes whatever
> the scan cadence.  A store made while the daemon is scanning rather than
> sleeping is lost, so the helper keeps storing until the pass lands.
>
> One wake completes one pass only if pages_to_scan covers every mm on the
> list, so callers need it large.
>
> Settings pushes must not start passes of their own.  A store to either
> sleep knob wakes the daemon, so thp_write_settings() now writes a
> khugepaged knob only when its value changes.
>
> Assisted-by: LLM
> Tested-by: Muhammad Usama Anjum <usama.anjum@xxxxxxx>
> Signed-off-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
> ---

Make sense to me.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>