Re: [PATCH v4 08/17] mm/mglru, smaps: convert to LRU refs based operations for MGLRU

[sashiko-bot@kernel.org]

> From: Kairui Song <kasong@tencent.com>
> 
> PG_referenced is only the lowest bit of the folio LRU refs count
> (LRU_REFS_FLAGS) now, and MGLRU never kept it stable: promotion used to
> clear it, and now it toggles as the count grows. But with the LRU
> referenced count as a stable API now, we can use two helpers to provide
> in-kernel users a stable and sane reading of the referenced status of
> an LRU managed folio.
> 
> Add folio_check_lru_refs() and folio_clear_lru_refs(), which use the refs
> count when MGLRU is enabled and PG_referenced otherwise, and switch the
> smaps paths over to them. The lru_gen_enabled() test stays inside the
> helpers, so its static key is not splattered over the few call sites.
> 
> Convert smaps as the first user of them. MGLRU now reports every folio
> with a nonzero count, so the reading no longer flickers and clearing no
> longer results in an ambiguous status.
> 
> The classical LRU case is unchanged.
> 
> Signed-off-by: Kairui Song <kasong@tencent.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261016-mglru-fg-v4-0-2106750c0bfa@tencent.com?part=8