+ mm-swap-delay-and-unify-memcg-lookup-and-charging-for-swapin.patch added to mm-new branch

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

The patch titled
     Subject: mm, swap: delay and unify memcg lookup and charging for swapin
has been added to the -mm mm-new branch.  Its filename is
     mm-swap-delay-and-unify-memcg-lookup-and-charging-for-swapin.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-swap-delay-and-unify-memcg-lookup-and-charging-for-swapin.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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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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------------------------------------------------------
From: Kairui Song <kasong@tencent.com>
Subject: mm, swap: delay and unify memcg lookup and charging for swapin
Date: Sun, 17 May 2026 23:39:47 +0800

Instead of checking the cgroup private ID during page table walk in
swap_pte_batch(), move the memcg lookup into __swap_cache_add_check()
under the cluster lock.

The first pre-alloc check is speculative and skips the memcg check since
the post-alloc stable check ensures all slots covered by the folio belong
to the same memcg.  It is very rare for contiguous and aligned entries
across a contiguous region of a page table of the same process or shmem
mapping to belong to different memcgs.

This also prepares for recording the memcg info in the cluster's table. 
Also make the order check and fallback more compact.

There should be no user-observable behavior change.

Link: https://lore.kernel.org/20260517-swap-table-p4-v5-8-88ae43e064c7@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 |    6 +++---
 mm/internal.h              |   10 +---------
 mm/memcontrol.c            |   10 ++++------
 mm/swap_state.c            |   28 +++++++++++++++++++---------
 4 files changed, 27 insertions(+), 27 deletions(-)

--- a/include/linux/memcontrol.h~mm-swap-delay-and-unify-memcg-lookup-and-charging-for-swapin
+++ a/include/linux/memcontrol.h
@@ -646,8 +646,8 @@ static inline int mem_cgroup_charge(stru
 
 int mem_cgroup_charge_hugetlb(struct folio* folio, gfp_t gfp);
 
-int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
-				  gfp_t gfp, swp_entry_t entry);
+int mem_cgroup_swapin_charge_folio(struct folio *folio, unsigned short id,
+				   struct mm_struct *mm, gfp_t gfp);
 
 void __mem_cgroup_uncharge(struct folio *folio);
 
@@ -1137,7 +1137,7 @@ static inline int mem_cgroup_charge_huge
 }
 
 static inline int mem_cgroup_swapin_charge_folio(struct folio *folio,
-			struct mm_struct *mm, gfp_t gfp, swp_entry_t entry)
+		 unsigned short id, struct mm_struct *mm, gfp_t gfp)
 {
 	return 0;
 }
--- a/mm/internal.h~mm-swap-delay-and-unify-memcg-lookup-and-charging-for-swapin
+++ a/mm/internal.h
@@ -451,24 +451,16 @@ static inline int swap_pte_batch(pte_t *
 {
 	pte_t expected_pte = pte_next_swp_offset(pte);
 	const pte_t *end_ptep = start_ptep + max_nr;
-	const softleaf_t entry = softleaf_from_pte(pte);
 	pte_t *ptep = start_ptep + 1;
-	unsigned short cgroup_id;
 
 	VM_WARN_ON(max_nr < 1);
-	VM_WARN_ON(!softleaf_is_swap(entry));
+	VM_WARN_ON(!softleaf_is_swap(softleaf_from_pte(pte)));
 
-	cgroup_id = lookup_swap_cgroup_id(entry);
 	while (ptep < end_ptep) {
-		softleaf_t entry;
-
 		pte = ptep_get(ptep);
 
 		if (!pte_same(pte, expected_pte))
 			break;
-		entry = softleaf_from_pte(pte);
-		if (lookup_swap_cgroup_id(entry) != cgroup_id)
-			break;
 		expected_pte = pte_next_swp_offset(expected_pte);
 		ptep++;
 	}
--- a/mm/memcontrol.c~mm-swap-delay-and-unify-memcg-lookup-and-charging-for-swapin
+++ a/mm/memcontrol.c
@@ -5076,27 +5076,25 @@ out:
 
 /**
  * mem_cgroup_swapin_charge_folio - Charge a newly allocated folio for swapin.
- * @folio: folio to charge.
+ * @folio: the folio to charge
+ * @id: memory cgroup id
  * @mm: mm context of the victim
  * @gfp: reclaim mode
- * @entry: swap entry for which the folio is allocated
  *
  * This function charges a folio allocated for swapin. Please call this before
  * adding the folio to the swapcache.
  *
  * Returns 0 on success. Otherwise, an error code is returned.
  */
-int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
-				  gfp_t gfp, swp_entry_t entry)
+int mem_cgroup_swapin_charge_folio(struct folio *folio, unsigned short id,
+				   struct mm_struct *mm, gfp_t gfp)
 {
 	struct mem_cgroup *memcg;
-	unsigned short id;
 	int ret;
 
 	if (mem_cgroup_disabled())
 		return 0;
 
-	id = lookup_swap_cgroup_id(entry);
 	rcu_read_lock();
 	memcg = mem_cgroup_from_private_id(id);
 	if (!memcg || !css_tryget_online(&memcg->css))
--- a/mm/swap_state.c~mm-swap-delay-and-unify-memcg-lookup-and-charging-for-swapin
+++ a/mm/swap_state.c
@@ -142,17 +142,21 @@ void *swap_cache_get_shadow(swp_entry_t
  * @ci: The locked swap cluster
  * @targ_entry: The target swap entry to check, will be rounded down by @nr
  * @nr: Number of slots to check, must be a power of 2
- * @shadowp: Returns the shadow value if one exists in the range.
+ * @shadowp: Returns the shadow value if one exists in the range
+ * @memcg_id: Returns the memory cgroup id, NULL to ignore cgroup check
  *
  * Check if all slots covered by given range have a swap count >= 1.
- * Retrieves the shadow if there is one.
+ * Retrieves the shadow if there is one. If @memcg_id is not NULL, also
+ * checks if all slots belong to the same cgroup and return the cgroup
+ * private id.
  *
  * Context: Caller must lock the cluster.
  * Return: 0 if success, error code if failed.
  */
 static int __swap_cache_add_check(struct swap_cluster_info *ci,
 				  swp_entry_t targ_entry,
-				  unsigned long nr, void **shadowp)
+				  unsigned long nr, void **shadowp,
+				  unsigned short *memcg_id)
 {
 	unsigned int ci_off, ci_end;
 	unsigned long old_tb;
@@ -172,19 +176,24 @@ static int __swap_cache_add_check(struct
 		return -EEXIST;
 	if (!__swp_tb_get_count(old_tb))
 		return -ENOENT;
-	if (swp_tb_is_shadow(old_tb) && shadowp)
+	if (shadowp && swp_tb_is_shadow(old_tb))
 		*shadowp = swp_tb_to_shadow(old_tb);
+	if (memcg_id)
+		*memcg_id = lookup_swap_cgroup_id(targ_entry);
 
 	if (nr == 1)
 		return 0;
 
+	targ_entry.val = round_down(targ_entry.val, nr);
 	ci_off = round_down(ci_off, nr);
 	ci_end = ci_off + nr;
 	do {
 		old_tb = __swap_table_get(ci, ci_off);
 		if (unlikely(swp_tb_is_folio(old_tb) ||
-			     !__swp_tb_get_count(old_tb)))
+			     !__swp_tb_get_count(old_tb) ||
+			     (memcg_id && *memcg_id != lookup_swap_cgroup_id(targ_entry))))
 			return -EBUSY;
+		targ_entry.val++;
 	} while (++ci_off < ci_end);
 
 	return 0;
@@ -400,6 +409,7 @@ static struct folio *__swap_cache_alloc(
 	swp_entry_t entry;
 	struct folio *folio;
 	void *shadow = NULL;
+	unsigned short memcg_id;
 	unsigned long address, nr_pages = 1UL << order;
 	struct vm_area_struct *vma = vmf ? vmf->vma : NULL;
 
@@ -408,7 +418,7 @@ static struct folio *__swap_cache_alloc(
 
 	/* Check if the slot and range are available, skip allocation if not */
 	spin_lock(&ci->lock);
-	err = __swap_cache_add_check(ci, targ_entry, nr_pages, NULL);
+	err = __swap_cache_add_check(ci, targ_entry, nr_pages, NULL, NULL);
 	spin_unlock(&ci->lock);
 	if (unlikely(err))
 		return ERR_PTR(err);
@@ -431,7 +441,7 @@ static struct folio *__swap_cache_alloc(
 
 	/* Double check the range is still not in conflict */
 	spin_lock(&ci->lock);
-	err = __swap_cache_add_check(ci, targ_entry, nr_pages, &shadow);
+	err = __swap_cache_add_check(ci, targ_entry, nr_pages, &shadow, &memcg_id);
 	if (unlikely(err)) {
 		spin_unlock(&ci->lock);
 		folio_put(folio);
@@ -443,8 +453,8 @@ static struct folio *__swap_cache_alloc(
 	__swap_cache_do_add_folio(ci, folio, entry);
 	spin_unlock(&ci->lock);
 
-	if (mem_cgroup_swapin_charge_folio(folio, vmf ? vmf->vma->vm_mm : NULL,
-					   gfp, entry)) {
+	if (mem_cgroup_swapin_charge_folio(folio, memcg_id,
+					   vmf ? vmf->vma->vm_mm : NULL, gfp)) {
 		spin_lock(&ci->lock);
 		__swap_cache_do_del_folio(ci, folio, entry, shadow);
 		spin_unlock(&ci->lock);
_

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