+ mm-mglru-fix-a-no-op-lru_gen_clear_refs-call-in-lru_lazyfree.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/mglru: fix a no-op lru_gen_clear_refs() call in lru_lazyfree()
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-mglru-fix-a-no-op-lru_gen_clear_refs-call-in-lru_lazyfree.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mglru-fix-a-no-op-lru_gen_clear_refs-call-in-lru_lazyfree.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Hui Zhu <zhuhui@kylinos.cn>
Subject: mm/mglru: fix a no-op lru_gen_clear_refs() call in lru_lazyfree()
Date: Mon,  9 Nov 2026 10:16:11 +0800

lru_lazyfree() calls lru_gen_clear_refs() after lruvec_del_folio(), but
lru_gen_del_folio() has already cleared LRU_GEN_MASK, so folio_lru_gen()
returns -1 and lru_gen_clear_refs() exits at its "gen < 0" check without
clearing the refs or PG_workingset.

A MADV_FREE folio therefore keeps the state it had before madvise(2),
even though madvise_free_pte_range() has already cleared the accessed and
dirty bits of its PTEs.  lru_gen_folio_seq() places it one generation
younger, and PG_workingset puts it in the last tier, so sort_folio()
promotes and protects it instead of evicting it and charges it to
lrugen->protected[], which read_ctrl_pos() uses to balance anon against
file reclaim.  __folio_inc_gen() clears the refs but not PG_workingset,
so this repeats every time the folio reaches the oldest generation.  If
the folio is redirtied first, ttu_anon_lazyfree_folio() keeps it and
lru_gen_eviction() packs the stale state into the shadow entry, so a
later refault is promoted to the youngest generation.

Call lru_gen_clear_refs() while the folio is still on the generation
list, as deactivate_file_folio() and folio_deactivate() already do.  Its
return value only says whether the folio is in the oldest generation,
which lru_lazyfree() does not need because it re-adds the folio below.
Keep folio_clear_referenced() unconditional: the classic LRU needs it,
and it also covers the folios that lru_gen_clear_refs() skips.

Link: https://lore.kernel.org/20261109021611.22247-1-hui.zhu@linux.dev
Fixes: cc8ec7be78ff ("mm/mglru: optimize deactivation")
Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Barry Song <baohua@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: <stable@vger.kernel.org>
---

 mm/folio.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/mm/folio.c~mm-mglru-fix-a-no-op-lru_gen_clear_refs-call-in-lru_lazyfree
+++ a/mm/folio.c
@@ -597,12 +597,10 @@ static void lru_lazyfree(struct lruvec *
 	    folio_test_swapcache(folio) || folio_test_unevictable(folio))
 		return;
 
+	lru_gen_clear_refs(folio);
 	lruvec_del_folio(lruvec, folio);
 	folio_clear_active(folio);
-	if (lru_gen_enabled())
-		lru_gen_clear_refs(folio);
-	else
-		folio_clear_referenced(folio);
+	folio_clear_referenced(folio);
 	/*
 	 * Lazyfree folios are clean anonymous folios.  They have
 	 * the swapbacked flag cleared, to distinguish them from normal
_

Patches currently in -mm which might be from zhuhui@kylinos.cn are

mm-mglru-fix-a-no-op-lru_gen_clear_refs-call-in-lru_lazyfree.patch
mm-vmstat-annotate-data-race-in-zone_page_state_snapshot.patch
mm-compaction-annotate-data-race-for-zone-free_areanr_free.patch