[to-be-updated] mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags.patch removed from -mm tree

[to-be-updated] mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/mglru: introduce helpers for manipulating gen and refs flags
has been removed from the -mm tree.  Its filename was
     mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags.patch

This patch was dropped because an updated version will be issued

------------------------------------------------------
From: Kairui Song <kasong@tencent.com>
Subject: mm/mglru: introduce helpers for manipulating gen and refs flags
Date: Wed, 26 Aug 2026 01:53:35 +0800

Instead of doing bit ops on folio->flags.f, introduce helpers for
adjusting a folio's refs and generation info, making the code easier to
debug and understand.

No functional change is intended: some combined atomic operations are
split into two, which only creates harmless transient states.  There is no
measurable performance impact, and some paths even look slightly better in
the generated assembly.

Link: https://lore.kernel.org/20260826-mglru-flags-cleanup-v3-2-d9f1c75549c8@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Qi Zheng <qi.zheng@linux.dev>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <baoquan.he@linux.dev>
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: Lian Wang <lianux.mm@gmail.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Ridong Chen <ridong.chen@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>
---

 include/linux/mm_inline.h |   78 +++++++++++++++++++++++++++++++-----
 include/linux/mmzone.h    |    1 
 mm/folio.c                |   19 +++++---
 mm/vmscan.c               |   61 +++++++++++++++-------------
 4 files changed, 115 insertions(+), 44 deletions(-)

--- a/include/linux/mm_inline.h~mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags
+++ a/include/linux/mm_inline.h
@@ -142,10 +142,42 @@ static inline int lru_tier_from_refs(int
 	return workingset ? MAX_NR_TIERS - 1 : order_base_2(refs);
 }
 
-static inline int folio_lru_refs(const struct folio *folio)
+/**
+ * lru_gen_from_flags - Return the LRU generation number from folio flags.
+ * @flags: folio flags
+ *
+ * Returns: A number between 0 and (MAX_NR_GENS - 1), inclusive. Returns
+ * -1 if the flags indicate the folio is off the list (e.g., isolated).
+ */
+static inline int lru_gen_from_flags(unsigned long flags)
+{
+	int gen = ((flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF);
+
+	BUILD_BUG_ON(LRU_GEN_MASK & LRU_REFS_MASK);
+	gen -= 1;
+	VM_WARN_ON_ONCE(gen != -1 && gen >= MAX_NR_GENS);
+	return gen;
+}
+
+/**
+ * lru_gen_set_flags - Set the LRU generation number to specified folio flags.
+ * @flags: pointer to the folio flags
+ * @gen: generation number, between 0 and (MAX_NR_GENS - 1), inclusive.
+ */
+static inline void lru_gen_set_flags(unsigned long *flags, int gen)
+{
+	VM_WARN_ON_ONCE(gen >= MAX_NR_GENS || gen < 0);
+
+	*flags &= ~LRU_GEN_MASK;
+	*flags |= (gen + 1UL) << LRU_GEN_PGOFF;
+}
+
+/**
+ * lru_refs_from_flags - Return LRU referenced / access count from folio flags.
+ * @flags: folio flags
+ */
+static inline int lru_refs_from_flags(unsigned long flags)
 {
-	unsigned long flags = READ_ONCE(folio->flags.f);
-
 	if (!(flags & BIT(PG_referenced)))
 		return 0;
 	/*
@@ -155,11 +187,40 @@ static inline int folio_lru_refs(const s
 	return ((flags & LRU_REFS_MASK) >> LRU_REFS_PGOFF) + 1;
 }
 
-static inline int folio_lru_gen(const struct folio *folio)
+/**
+ * lru_refs_set_flags - Set the LRU referenced / access count to specified folio flags.
+ * @flags: pointer to the folio flags
+ * @refs: referenced / access count number, between 0 and LRU_REFS_MAX, inclusive.
+ */
+static inline void lru_refs_set_flags(unsigned long *flags, unsigned int refs)
 {
-	unsigned long flags = READ_ONCE(folio->flags.f);
+	VM_WARN_ON_ONCE(refs > LRU_REFS_MAX);
+	BUILD_BUG_ON(LRU_REFS_MAX != (LRU_REFS_MASK >> LRU_REFS_PGOFF) + 1);
 
-	return ((flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
+	*flags &= ~LRU_REFS_FLAGS;
+	if (!refs)
+		return;
+	*flags |= (BIT(PG_referenced) | ((refs - 1UL) << LRU_REFS_PGOFF));
+}
+
+static inline int folio_lru_refs(const struct folio *folio)
+{
+	return lru_refs_from_flags(READ_ONCE(*const_folio_flags(folio, 0)));
+}
+
+static inline void folio_set_lru_refs(struct folio *folio, unsigned int refs)
+{
+	unsigned long new_flags, old_flags = READ_ONCE(*folio_flags(folio, 0));
+
+	do {
+		new_flags = old_flags;
+		lru_refs_set_flags(&new_flags, refs);
+	} while (!try_cmpxchg(folio_flags(folio, 0), &old_flags, new_flags));
+}
+
+static inline int folio_lru_gen(const struct folio *folio)
+{
+	return lru_gen_from_flags(READ_ONCE(*const_folio_flags(folio, 0)));
 }
 
 static inline bool lru_gen_is_active(const struct lruvec *lruvec, int gen)
@@ -270,7 +331,7 @@ static inline bool lru_gen_add_folio(str
 	gen = lru_gen_from_seq(seq);
 	flags = (gen + 1UL) << LRU_GEN_PGOFF;
 	/* see the comment on MIN_NR_GENS about PG_active */
-	set_mask_bits(&folio->flags.f, LRU_GEN_MASK | BIT(PG_active), flags);
+	set_mask_bits(folio_flags(folio, 0), LRU_GEN_MASK | BIT(PG_active), flags);
 
 	lru_gen_update_size(lruvec, folio, -1, gen);
 	/* for folio_rotate_reclaimable() */
@@ -295,7 +356,7 @@ static inline bool lru_gen_del_folio(str
 
 	/* for folio_migrate_flags() */
 	flags = !reclaiming && lru_gen_is_active(lruvec, gen) ? BIT(PG_active) : 0;
-	flags = set_mask_bits(&folio->flags.f, LRU_GEN_MASK, flags);
+	flags = set_mask_bits(folio_flags(folio, 0), LRU_GEN_MASK, flags);
 	gen = ((flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
 
 	lru_gen_update_size(lruvec, folio, gen, -1);
@@ -339,7 +400,6 @@ static inline bool lru_gen_del_folio(str
 
 static inline void folio_migrate_refs(struct folio *new, const struct folio *old)
 {
-
 }
 #endif /* CONFIG_LRU_GEN */
 
--- a/include/linux/mmzone.h~mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags
+++ a/include/linux/mmzone.h
@@ -500,6 +500,7 @@ enum lruvec_flags {
 
 #define LRU_GEN_MASK		((BIT(LRU_GEN_WIDTH) - 1) << LRU_GEN_PGOFF)
 #define LRU_REFS_MASK		((BIT(LRU_REFS_WIDTH) - 1) << LRU_REFS_PGOFF)
+#define LRU_REFS_MAX		BIT(LRU_REFS_WIDTH)
 
 /*
  * For folios accessed multiple times through file descriptors,
--- a/mm/folio.c~mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags
+++ a/mm/folio.c
@@ -353,26 +353,28 @@ static void __lru_cache_activate_folio(s
 
 static void lru_gen_inc_refs(struct folio *folio)
 {
-	unsigned long new_flags, old_flags = READ_ONCE(folio->flags.f);
+	unsigned long new_flags, old_flags = READ_ONCE(*folio_flags(folio, 0));
+	int refs;
 
 	if (folio_test_unevictable(folio))
 		return;
 
 	/* see the comment on LRU_REFS_FLAGS */
-	if (!folio_test_referenced(folio)) {
-		set_mask_bits(&folio->flags.f, LRU_REFS_MASK, BIT(PG_referenced));
+	if (!folio_lru_refs(folio)) {
+		folio_set_lru_refs(folio, 1);
 		return;
 	}
 
 	do {
-		if ((old_flags & LRU_REFS_MASK) == LRU_REFS_MASK) {
+		new_flags = old_flags;
+		refs = lru_refs_from_flags(old_flags);
+		if (refs == LRU_REFS_MAX) {
 			if (!folio_test_workingset(folio))
 				folio_set_workingset(folio);
 			return;
 		}
-
-		new_flags = old_flags + BIT(LRU_REFS_PGOFF);
-	} while (!try_cmpxchg(&folio->flags.f, &old_flags, new_flags));
+		lru_refs_set_flags(&new_flags, refs + 1);
+	} while (!try_cmpxchg(folio_flags(folio, 0), &old_flags, new_flags));
 }
 
 static bool lru_gen_clear_refs(struct folio *folio)
@@ -384,7 +386,8 @@ static bool lru_gen_clear_refs(struct fo
 	if (gen < 0)
 		return true;
 
-	set_mask_bits(&folio->flags.f, LRU_REFS_FLAGS | BIT(PG_workingset), 0);
+	folio_set_lru_refs(folio, 0);
+	folio_clear_workingset(folio);
 
 	rcu_read_lock();
 	seq = READ_ONCE(folio_lruvec(folio)->lrugen.min_seq[type]);
--- a/mm/vmscan.c~mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags
+++ a/mm/vmscan.c
@@ -843,19 +843,22 @@ static bool lru_gen_set_refs(struct foli
 	if (!folio_test_referenced(folio) && !folio_test_workingset(folio)) {
 		/* Activate file-backed executable folios after first usage. */
 		if (is_exec_file_folio(folio, vma_flags)) {
-			set_mask_bits(&folio->flags.f, LRU_REFS_FLAGS, BIT(PG_workingset));
+			folio_set_workingset(folio);
+			folio_set_lru_refs(folio, 0);
 			return true;
 		}
 
-		set_mask_bits(&folio->flags.f, LRU_REFS_MASK, BIT(PG_referenced));
+		folio_set_lru_refs(folio, 1);
 		return false;
 	}
 
 	/* Promote on second access */
-	if (folio_lru_refs(folio) > 1)
-		set_mask_bits(&folio->flags.f, LRU_REFS_FLAGS, BIT(PG_workingset));
-	else
+	if (folio_lru_refs(folio) > 1) {
+		folio_set_workingset(folio);
+		folio_set_lru_refs(folio, 0);
+	} else {
 		folio_mark_accessed(folio);
+	}
 	return true;
 }
 #else
@@ -3266,11 +3269,10 @@ static bool positive_ctrl_err(struct ctr
  ******************************************************************************/
 
 /* promote pages accessed through page tables */
-static int folio_update_gen(struct folio *folio, int gen, const vma_flags_t *vma_flags)
+static int folio_update_gen(struct folio *folio, int new_gen, const vma_flags_t *vma_flags)
 {
-	unsigned long new_flags, old_flags = READ_ONCE(folio->flags.f);
-
-	VM_WARN_ON_ONCE(gen >= MAX_NR_GENS);
+	unsigned long new_flags, old_flags = READ_ONCE(*folio_flags(folio, 0));
+	int old_gen;
 
 	/*
 	 * See the comment on LRU_REFS_FLAGS, and activate file-backed
@@ -3279,20 +3281,24 @@ static int folio_update_gen(struct folio
 	 */
 	if (!folio_test_referenced(folio) && !folio_test_workingset(folio) &&
 	    !is_exec_file_folio(folio, vma_flags)) {
-		set_mask_bits(&folio->flags.f, LRU_REFS_MASK, BIT(PG_referenced));
+		folio_set_lru_refs(folio, 1);
 		return -1;
 	}
 
 	do {
+		old_gen = lru_gen_from_flags(old_flags);
+		new_flags = old_flags;
+
 		/* lru_gen_del_folio() has isolated this page? */
-		if (!(old_flags & LRU_GEN_MASK))
-			return -1;
+		if (old_gen < 0)
+			break;
 
-		new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_FLAGS);
-		new_flags |= ((gen + 1UL) << LRU_GEN_PGOFF) | BIT(PG_workingset);
-	} while (!try_cmpxchg(&folio->flags.f, &old_flags, new_flags));
+		lru_gen_set_flags(&new_flags, new_gen);
+		lru_refs_set_flags(&new_flags, 0);
+		new_flags |= BIT(PG_workingset);
+	} while (!try_cmpxchg(folio_flags(folio, 0), &old_flags, new_flags));
 
-	return ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
+	return old_gen;
 }
 
 /* protect pages accessed multiple times through file descriptors */
@@ -3301,21 +3307,20 @@ static int folio_inc_gen(struct lruvec *
 	int type = folio_is_file_lru(folio);
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
 	int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
-	unsigned long new_flags, old_flags = READ_ONCE(folio->flags.f);
-
-	VM_WARN_ON_ONCE_FOLIO(!(old_flags & LRU_GEN_MASK), folio);
+	unsigned long new_flags, old_flags = READ_ONCE(*folio_flags(folio, 0));
 
 	do {
-		new_gen = ((old_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
+		new_gen = lru_gen_from_flags(old_flags);
+
 		/* folio_update_gen() has promoted this page? */
 		if (new_gen >= 0 && new_gen != old_gen)
 			return new_gen;
 
+		new_flags = old_flags;
 		new_gen = (old_gen + 1) % MAX_NR_GENS;
-
-		new_flags = old_flags & ~(LRU_GEN_MASK | LRU_REFS_FLAGS);
-		new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF;
-	} while (!try_cmpxchg(&folio->flags.f, &old_flags, new_flags));
+		lru_gen_set_flags(&new_flags, new_gen);
+		lru_refs_set_flags(&new_flags, 0);
+	} while (!try_cmpxchg(folio_flags(folio, 0), &old_flags, new_flags));
 
 	lru_gen_update_size(lruvec, folio, old_gen, new_gen);
 
@@ -4716,7 +4721,7 @@ static bool isolate_folio(struct lruvec
 
 	/* see the comment on LRU_REFS_FLAGS */
 	if (!folio_test_referenced(folio))
-		set_mask_bits(&folio->flags.f, LRU_REFS_MASK, 0);
+		folio_set_lru_refs(folio, 0);
 
 	success = lru_gen_del_folio(lruvec, folio, true);
 	VM_WARN_ON_ONCE_FOLIO(!success, folio);
@@ -4932,8 +4937,10 @@ retry:
 		}
 
 		/* don't add rejected folios to the oldest generation */
-		if (lru_gen_folio_seq(lruvec, folio, false) == min_seq[type])
-			set_mask_bits(&folio->flags.f, LRU_REFS_FLAGS, BIT(PG_active));
+		if (lru_gen_folio_seq(lruvec, folio, false) == min_seq[type]) {
+			folio_set_lru_refs(folio, 0);
+			folio_set_active(folio);
+		}
 	}
 
 	move_folios_to_lru(&list);
_

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

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