+ mm-mglru-move-max_seq-read-into-walk_update_folio.patch added to mm-new branch

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

The patch titled
     Subject: mm/mglru: move max_seq read into walk_update_folio
has been added to the -mm mm-new branch.  Its filename is
     mm-mglru-move-max_seq-read-into-walk_update_folio.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mglru-move-max_seq-read-into-walk_update_folio.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Kairui Song <kasong@tencent.com>
Subject: mm/mglru: move max_seq read into walk_update_folio
Date: Wed, 26 Aug 2026 01:53:37 +0800

walk_pte_range(), walk_pmd_range_locked(), and lru_gen_look_around() each
read lrugen->max_seq to compute the target generation used by
walk_update_folio(), then pass it as a parameter.  Move the read into
walk_update_folio() itself so the callers no longer need to compute or
pass the value.

The max_seq read now happens once per folio update rather than once per
walk range, so folios always get promoted to the current youngest
generation.

Link: https://lore.kernel.org/20260826-mglru-flags-cleanup-v3-4-d9f1c75549c8@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baoquan He <baoquan.he@linux.dev>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Ridong Chen <ridong.chen@linux.dev>
Reviewed-by: Lian Wang <lianux.mm@gmail.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |   29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

--- a/mm/vmscan.c~mm-mglru-move-max_seq-read-into-walk_update_folio
+++ a/mm/vmscan.c
@@ -3517,13 +3517,15 @@ static bool suitable_to_scan(int total,
 }
 
 static void walk_update_folio(struct lru_gen_mm_walk *walk, struct vm_area_struct *vma,
-		struct folio *folio, int new_gen, bool dirty)
+		struct lruvec *lruvec, struct folio *folio, bool dirty)
 {
-	int old_gen;
+	int new_gen, old_gen;
 
 	if (!folio)
 		return;
 
+	new_gen = lru_gen_from_seq(READ_ONCE(lruvec->lrugen.max_seq));
+
 	if (dirty && !folio_test_dirty(folio) &&
 	    !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
 	      !folio_test_swapcache(folio)))
@@ -3554,8 +3556,6 @@ static bool walk_pte_range(pmd_t *pmd, u
 	struct lru_gen_mm_walk *walk = args->private;
 	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
-	DEFINE_MAX_SEQ(walk->lruvec);
-	int gen = lru_gen_from_seq(max_seq);
 	unsigned int nr;
 	pmd_t pmdval;
 
@@ -3606,7 +3606,7 @@ restart:
 			continue;
 
 		if (last != folio) {
-			walk_update_folio(walk, args->vma, last, gen, dirty);
+			walk_update_folio(walk, args->vma, walk->lruvec, last, dirty);
 
 			last = folio;
 			dirty = false;
@@ -3619,7 +3619,7 @@ restart:
 		walk->mm_stats[MM_LEAF_YOUNG] += nr;
 	}
 
-	walk_update_folio(walk, args->vma, last, gen, dirty);
+	walk_update_folio(walk, args->vma, walk->lruvec, last, dirty);
 	last = NULL;
 
 	if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
@@ -3642,8 +3642,6 @@ static void walk_pmd_range_locked(pud_t
 	struct lru_gen_mm_walk *walk = args->private;
 	struct mem_cgroup *memcg = lruvec_memcg(walk->lruvec);
 	struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
-	DEFINE_MAX_SEQ(walk->lruvec);
-	int gen = lru_gen_from_seq(max_seq);
 
 	VM_WARN_ON_ONCE(pud_leaf(*pud));
 
@@ -3697,7 +3695,7 @@ static void walk_pmd_range_locked(pud_t
 			goto next;
 
 		if (last != folio) {
-			walk_update_folio(walk, vma, last, gen, dirty);
+			walk_update_folio(walk, vma, walk->lruvec, last, dirty);
 
 			last = folio;
 			dirty = false;
@@ -3711,7 +3709,7 @@ next:
 		i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1;
 	} while (i <= MIN_LRU_BATCH);
 
-	walk_update_folio(walk, vma, last, gen, dirty);
+	walk_update_folio(walk, vma, walk->lruvec, last, dirty);
 
 	lazy_mmu_mode_disable();
 	spin_unlock(ptl);
@@ -4275,8 +4273,6 @@ bool lru_gen_look_around(struct page_vma
 	struct pglist_data *pgdat = folio_pgdat(folio);
 	struct lruvec *lruvec;
 	struct lru_gen_mm_state *mm_state;
-	unsigned long max_seq;
-	int gen;
 
 	lockdep_assert_held(pvmw->ptl);
 	VM_WARN_ON_ONCE_FOLIO(folio_test_lru(folio), folio);
@@ -4313,8 +4309,6 @@ bool lru_gen_look_around(struct page_vma
 
 	memcg = get_mem_cgroup_from_folio(folio);
 	lruvec = mem_cgroup_lruvec(memcg, pgdat);
-	max_seq = READ_ONCE((lruvec)->lrugen.max_seq);
-	gen = lru_gen_from_seq(max_seq);
 	mm_state = get_mm_state(lruvec);
 
 	lazy_mmu_mode_enable();
@@ -4346,7 +4340,7 @@ bool lru_gen_look_around(struct page_vma
 			continue;
 
 		if (last != folio) {
-			walk_update_folio(walk, vma, last, gen, dirty);
+			walk_update_folio(walk, vma, lruvec, last, dirty);
 
 			last = folio;
 			dirty = false;
@@ -4358,13 +4352,14 @@ bool lru_gen_look_around(struct page_vma
 		young += nr;
 	}
 
-	walk_update_folio(walk, vma, last, gen, dirty);
+	walk_update_folio(walk, vma, lruvec, last, dirty);
 
 	lazy_mmu_mode_disable();
 
 	/* feedback from rmap walkers to page table walkers */
 	if (mm_state && suitable_to_scan(i, young))
-		update_bloom_filter(mm_state, max_seq, pvmw->pmd);
+		update_bloom_filter(mm_state, READ_ONCE(lruvec->lrugen.max_seq),
+				    pvmw->pmd);
 
 	mem_cgroup_put(memcg);
 
_

Patches currently in -mm which might be from kasong@tencent.com are

mm-memcontrol-make-lru_zone_size-atomic-and-simplify-sanity-check.patch
mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags.patch
mm-migrate-copy-all-referenced-state-via-folio_migrate_lru_refs.patch
mm-mglru-move-max_seq-read-into-walk_update_folio.patch
mm-mglru-use-explicit-tier-range-in-read_ctrl_pos.patch
mm-mglru-fix-potential-generation-folio-number-leak.patch