2 files changed, 18 insertions, 19 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 38f94c7271c1..12982875073e 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -741,7 +741,15 @@ out:
  * folio_lruvec - return lruvec for isolating/putting an LRU folio
  * @folio: Pointer to the folio.
  *
- * This function relies on folio->mem_cgroup being stable.
+ * Call with rcu_read_lock() held to ensure the lifetime of the returned lruvec.
+ * Note that this alone will NOT guarantee the stability of the folio->lruvec
+ * association; the folio can be reparented to an ancestor if this races with
+ * cgroup deletion.
+ *
+ * Use folio_lruvec_lock() to ensure both lifetime and stability of the binding.
+ * Once a lruvec is locked, folio_lruvec() can be called on other folios, and
+ * their binding is stable if the returned lruvec matches the one the caller has
+ * locked. Useful for lock batching.
  */
 static inline struct lruvec *folio_lruvec(struct folio *folio)
 {
@@ -764,15 +772,6 @@ struct lruvec *folio_lruvec_lock_irq(struct folio *folio);
 struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,
 						unsigned long *flags);
 
-#ifdef CONFIG_DEBUG_VM
-void lruvec_memcg_debug(struct lruvec *lruvec, struct folio *folio);
-#else
-static inline
-void lruvec_memcg_debug(struct lruvec *lruvec, struct folio *folio)
-{
-}
-#endif
-
 static inline
 struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css){
 	return css ? container_of(css, struct mem_cgroup, css) : NULL;
@@ -1198,11 +1197,6 @@ static inline struct lruvec *folio_lruvec(struct folio *folio)
 	return &pgdat->__lruvec;
 }
 
-static inline
-void lruvec_memcg_debug(struct lruvec *lruvec, struct folio *folio)
-{
-}
-
 static inline struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
 {
 	return NULL;
@@ -1261,6 +1255,7 @@ static inline struct lruvec *folio_lruvec_lock(struct folio *folio)
 {
 	struct pglist_data *pgdat = folio_pgdat(folio);
 
+	rcu_read_lock();
 	spin_lock(&pgdat->__lruvec.lru_lock);
 	return &pgdat->__lruvec;
 }
@@ -1269,6 +1264,7 @@ static inline struct lruvec *folio_lruvec_lock_irq(struct folio *folio)
 {
 	struct pglist_data *pgdat = folio_pgdat(folio);
 
+	rcu_read_lock();
 	spin_lock_irq(&pgdat->__lruvec.lru_lock);
 	return &pgdat->__lruvec;
 }
@@ -1278,6 +1274,7 @@ static inline struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,
 {
 	struct pglist_data *pgdat = folio_pgdat(folio);
 
+	rcu_read_lock();
 	spin_lock_irqsave(&pgdat->__lruvec.lru_lock, *flagsp);
 	return &pgdat->__lruvec;
 }
@@ -1500,23 +1497,26 @@ static inline struct lruvec *parent_lruvec(struct lruvec *lruvec)
 
 static inline void lruvec_lock_irq(struct lruvec *lruvec)
 {
+	rcu_read_lock();
 	spin_lock_irq(&lruvec->lru_lock);
 }
 
 static inline void lruvec_unlock(struct lruvec *lruvec)
 {
 	spin_unlock(&lruvec->lru_lock);
+	rcu_read_unlock();
 }
 
 static inline void lruvec_unlock_irq(struct lruvec *lruvec)
 {
 	spin_unlock_irq(&lruvec->lru_lock);
+	rcu_read_unlock();
 }
 
-static inline void lruvec_unlock_irqrestore(struct lruvec *lruvec,
-		unsigned long flags)
+static inline void lruvec_unlock_irqrestore(struct lruvec *lruvec, unsigned long flags)
 {
 	spin_unlock_irqrestore(&lruvec->lru_lock, flags);
+	rcu_read_unlock();
 }
 
 /* Test requires a stable folio->memcg binding, see folio_memcg() */
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 4b1f13b5bbad..ea08e2afa2b4 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -310,8 +310,7 @@ extern unsigned long totalreserve_pages;
 
 /* linux/mm/swap.c */
 void lru_note_cost_unlock_irq(struct lruvec *lruvec, bool file,
-		unsigned int nr_io, unsigned int nr_rotated)
-		__releases(lruvec->lru_lock);
+		unsigned int nr_io, unsigned int nr_rotated);
 void lru_note_cost_refault(struct folio *);
 void folio_add_lru(struct folio *);
 void folio_add_lru_vma(struct folio *, struct vm_area_struct *);