+ mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers.patch added to mm-new branch

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

The patch titled
     Subject: mm/memcg, swap: tidy up cgroup v1 memsw swap helpers
has been added to the -mm mm-new branch.  Its filename is
     mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers.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/memcg, swap: tidy up cgroup v1 memsw swap helpers
Date: Sun, 17 May 2026 23:39:45 +0800

The cgroup v1 swap helpers always operate on swap cache folios whose swap
entry is stable: the folio is locked and in the swap cache.  There is no
need to pass the swap entry or page count as separate parameters when they
can be derived from the folio itself.

Simplify the redundant parameters and add sanity checks to document the
required preconditions.

Also rename memcg1_swapout to __memcg1_swapout to indicate it requires
special calling context: the folio must be isolated and dying, and the
call must be made with interrupts disabled.

No functional change.

Link: https://lore.kernel.org/20260517-swap-table-p4-v5-6-88ae43e064c7@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Youngjun Park <youngjun.park@lge.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/memcontrol.h |    8 ++++----
 include/linux/swap.h       |   10 ++++------
 mm/huge_memory.c           |    2 +-
 mm/memcontrol-v1.c         |   33 ++++++++++++++++++++-------------
 mm/memcontrol.c            |    9 ++++-----
 mm/swap_state.c            |    4 ++--
 mm/swapfile.c              |    2 +-
 mm/vmscan.c                |    2 +-
 8 files changed, 37 insertions(+), 33 deletions(-)

--- a/include/linux/memcontrol.h~mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers
+++ a/include/linux/memcontrol.h
@@ -1899,8 +1899,8 @@ static inline void mem_cgroup_exit_user_
 	current->in_user_fault = 0;
 }
 
-void memcg1_swapout(struct folio *folio, swp_entry_t entry);
-void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages);
+void __memcg1_swapout(struct folio *folio);
+void memcg1_swapin(struct folio *folio);
 
 #else /* CONFIG_MEMCG_V1 */
 static inline
@@ -1929,11 +1929,11 @@ static inline void mem_cgroup_exit_user_
 {
 }
 
-static inline void memcg1_swapout(struct folio *folio, swp_entry_t entry)
+static inline void __memcg1_swapout(struct folio *folio)
 {
 }
 
-static inline void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages)
+static inline void memcg1_swapin(struct folio *folio)
 {
 }
 
--- a/include/linux/swap.h~mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers
+++ a/include/linux/swap.h
@@ -576,13 +576,12 @@ static inline void folio_throttle_swapra
 #endif
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_SWAP)
-int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry);
-static inline int mem_cgroup_try_charge_swap(struct folio *folio,
-		swp_entry_t entry)
+int __mem_cgroup_try_charge_swap(struct folio *folio);
+static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 {
 	if (mem_cgroup_disabled())
 		return 0;
-	return __mem_cgroup_try_charge_swap(folio, entry);
+	return __mem_cgroup_try_charge_swap(folio);
 }
 
 extern void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
@@ -596,8 +595,7 @@ static inline void mem_cgroup_uncharge_s
 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
 extern bool mem_cgroup_swap_full(struct folio *folio);
 #else
-static inline int mem_cgroup_try_charge_swap(struct folio *folio,
-					     swp_entry_t entry)
+static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 {
 	return 0;
 }
--- a/mm/huge_memory.c~mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers
+++ a/mm/huge_memory.c
@@ -4430,7 +4430,7 @@ void deferred_split_folio(struct folio *
 
 	/*
 	 * Exclude swapcache: originally to avoid a corrupt deferred split
-	 * queue. Nowadays that is fully prevented by memcg1_swapout();
+	 * queue. Nowadays that is fully prevented by __memcg1_swapout();
 	 * but if page reclaim is already handling the same folio, it is
 	 * unnecessary to handle it again in the shrinker, so excluding
 	 * swapcache here may still be a useful optimization.
--- a/mm/memcontrol.c~mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers
+++ a/mm/memcontrol.c
@@ -5470,13 +5470,12 @@ int __init mem_cgroup_init(void)
 /**
  * __mem_cgroup_try_charge_swap - try charging swap space for a folio
  * @folio: folio being added to swap
- * @entry: swap entry to charge
  *
- * Try to charge @folio's memcg for the swap space at @entry.
+ * Try to charge @folio's memcg for the swap space at folio->swap.
  *
  * Returns 0 on success, -ENOMEM on failure.
  */
-int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry)
+int __mem_cgroup_try_charge_swap(struct folio *folio)
 {
 	unsigned int nr_pages = folio_nr_pages(folio);
 	struct page_counter *counter;
@@ -5493,7 +5492,7 @@ int __mem_cgroup_try_charge_swap(struct
 
 	rcu_read_lock();
 	memcg = obj_cgroup_memcg(objcg);
-	if (!entry.val) {
+	if (!folio_test_swapcache(folio)) {
 		memcg_memory_event(memcg, MEMCG_SWAP_FAIL);
 		rcu_read_unlock();
 		return 0;
@@ -5512,7 +5511,7 @@ int __mem_cgroup_try_charge_swap(struct
 	}
 	mod_memcg_state(memcg, MEMCG_SWAP, nr_pages);
 
-	swap_cgroup_record(folio, mem_cgroup_private_id(memcg), entry);
+	swap_cgroup_record(folio, mem_cgroup_private_id(memcg), folio->swap);
 
 	return 0;
 }
--- a/mm/memcontrol-v1.c~mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers
+++ a/mm/memcontrol-v1.c
@@ -604,18 +604,23 @@ void memcg1_commit_charge(struct folio *
 }
 
 /**
- * memcg1_swapout - transfer a memsw charge to swap
+ * __memcg1_swapout - transfer a memsw charge to swap
  * @folio: folio whose memsw charge to transfer
- * @entry: swap entry to move the charge to
  *
- * Transfer the memsw charge of @folio to @entry.
+ * Transfer the memsw charge of @folio to the swap entry stored in
+ * folio->swap.
+ *
+ * Context: folio must be isolated, unmapped, locked and is just about
+ * to be freed, and caller must disable IRQs.
  */
-void memcg1_swapout(struct folio *folio, swp_entry_t entry)
+void __memcg1_swapout(struct folio *folio)
 {
 	struct mem_cgroup *memcg, *swap_memcg;
 	struct obj_cgroup *objcg;
 	unsigned int nr_entries;
 
+	VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
+	VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
 	VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
 	VM_BUG_ON_FOLIO(folio_ref_count(folio), folio);
 
@@ -641,7 +646,7 @@ void memcg1_swapout(struct folio *folio,
 	swap_memcg = mem_cgroup_private_id_get_online(memcg, nr_entries);
 	mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);
 
-	swap_cgroup_record(folio, mem_cgroup_private_id(swap_memcg), entry);
+	swap_cgroup_record(folio, mem_cgroup_private_id(swap_memcg), folio->swap);
 
 	folio_unqueue_deferred_split(folio);
 	folio->memcg_data = 0;
@@ -671,18 +676,20 @@ void memcg1_swapout(struct folio *folio,
 	obj_cgroup_put(objcg);
 }
 
-/*
+/**
  * memcg1_swapin - uncharge swap slot
- * @entry: the first swap entry for which the pages are charged
- * @nr_pages: number of pages which will be uncharged
+ * @folio: folio being swapped in
  *
- * Call this function after successfully adding the charged page to swapcache.
+ * Call this function after successfully adding the charged
+ * folio to swapcache.
  *
- * Note: This function assumes the page for which swap slot is being uncharged
- * is order 0 page.
+ * Context: The folio has to be in swap cache and locked.
  */
-void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages)
+void memcg1_swapin(struct folio *folio)
 {
+	VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
+	VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
+
 	/*
 	 * Cgroup1's unified memory+swap counter has been charged with the
 	 * new swapcache page, finish the transfer by uncharging the swap
@@ -701,7 +708,7 @@ void memcg1_swapin(swp_entry_t entry, un
 		 * let's not wait for it.  The page already received a
 		 * memory+swap charge, drop the swap entry duplicate.
 		 */
-		mem_cgroup_uncharge_swap(entry, nr_pages);
+		mem_cgroup_uncharge_swap(folio->swap, folio_nr_pages(folio));
 	}
 }
 
--- a/mm/swapfile.c~mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers
+++ a/mm/swapfile.c
@@ -1749,7 +1749,7 @@ again:
 	}
 
 	/* Need to call this even if allocation failed, for MEMCG_SWAP_FAIL. */
-	if (unlikely(mem_cgroup_try_charge_swap(folio, folio->swap)))
+	if (unlikely(mem_cgroup_try_charge_swap(folio)))
 		swap_cache_del_folio(folio);
 
 	if (unlikely(!folio_test_swapcache(folio)))
--- a/mm/swap_state.c~mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers
+++ a/mm/swap_state.c
@@ -455,8 +455,8 @@ static struct folio *__swap_cache_alloc(
 		return ERR_PTR(-ENOMEM);
 	}
 
-	/* For memsw accounting, swap is uncharged when folio is added to swap cache */
-	memcg1_swapin(entry, 1 << order);
+	/* memsw uncharges swap when folio is added to swap cache */
+	memcg1_swapin(folio);
 	if (shadow)
 		workingset_refault(folio, shadow);
 
--- a/mm/vmscan.c~mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers
+++ a/mm/vmscan.c
@@ -737,7 +737,7 @@ static int __remove_mapping(struct addre
 
 		if (reclaimed && !mapping_exiting(mapping))
 			shadow = workingset_eviction(folio, target_memcg);
-		memcg1_swapout(folio, swap);
+		__memcg1_swapout(folio);
 		__swap_cache_del_folio(ci, folio, swap, shadow);
 		swap_cluster_unlock_irq(ci);
 	} else {
_

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

mm-mglru-consolidate-common-code-for-retrieving-evictable-size.patch
mm-mglru-rename-variables-related-to-aging-and-rotation.patch
mm-mglru-relocate-the-lru-scan-batch-limit-to-callers.patch
mm-mglru-restructure-the-reclaim-loop.patch
mm-mglru-scan-and-count-the-exact-number-of-folios.patch
mm-mglru-use-a-smaller-batch-for-reclaim.patch
mm-mglru-dont-abort-scan-immediately-right-after-aging.patch
mm-mglru-remove-redundant-swap-constrained-check-upon-isolation.patch
mm-mglru-use-the-common-routine-for-dirty-writeback-reactivation.patch
mm-mglru-simplify-and-improve-dirty-writeback-handling.patch
mm-mglru-remove-no-longer-used-reclaim-argument-for-folio-protection.patch
mm-vmscan-remove-sc-file_taken.patch
mm-vmscan-remove-sc-unqueued_dirty.patch
mm-vmscan-unify-writeback-reclaim-statistic-and-throttling.patch
mm-swap-avoid-leaving-unused-extend-table-after-alloc-race.patch
mm-swap-simplify-swap-cache-allocation-helper.patch
mm-swap-move-common-swap-cache-operations-into-standalone-helpers.patch
mm-huge_memory-move-thp-gfp-limit-helper-into-header.patch
mm-swap-add-support-for-stable-large-allocation-in-swap-cache-directly.patch
mm-swap-unify-large-folio-allocation.patch
mm-memcg-swap-tidy-up-cgroup-v1-memsw-swap-helpers.patch
mm-swap-support-flexible-batch-freeing-of-slots-in-different-memcgs.patch
mm-swap-delay-and-unify-memcg-lookup-and-charging-for-swapin.patch
mm-swap-consolidate-cluster-allocation-helpers.patch
mm-memcg-swap-store-cgroup-id-in-cluster-table-directly.patch
mm-memcg-remove-no-longer-used-swap-cgroup-array.patch
mm-swap-merge-zeromap-into-swap-table.patch