Re: [PATCH] f2fs: annotate lockless last_time[] accesses

[Chao Yu]

On 5/6/26 09:07, Cen Zhang wrote:
> f2fs stores mount-wide activity timestamps in sbi->last_time[] and
> samples them from background discard, GC, and balance paths without a
> dedicated lock. The timestamps are used as best-effort heuristics to
> decide whether background work should run now or sleep a bit longer.
>
> The current helpers use plain loads and stores, so KCSAN can report races
> between frequent foreground updates and background readers. Exact
> freshness is not required here, but the intentional lockless accesses
> should be marked explicitly.
>
> Use WRITE_ONCE() in f2fs_update_time() and READ_ONCE() in
> f2fs_time_over() and f2fs_time_to_wait(). This preserves the existing
> heuristic behavior and avoids adding locking to hot paths.
>
> Signed-off-by: Cen Zhang <zzzccc427@xxxxxxxxx>

Reviewed-by: Chao Yu <chao@xxxxxxxxxx>

Thanks,