+ mm-huge_memory-count-only-swap-cache-refs-in-anon-folio-split.patch added to mm-unstable branch

+ mm-huge_memory-count-only-swap-cache-refs-in-anon-folio-split.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/huge_memory: count only swap cache refs in anon folio split
has been added to the -mm mm-unstable branch.  Its filename is
     mm-huge_memory-count-only-swap-cache-refs-in-anon-folio-split.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-huge_memory-count-only-swap-cache-refs-in-anon-folio-split.patch

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

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------------------------------------------------------
From: Kairui Song <kasong@tencent.com>
Subject: mm/huge_memory: count only swap cache refs in anon folio split
Date: Wed, 23 Sep 2026 23:32:47 +0200

Only __folio_freeze_split_anon() sees anon folios and swap cache folios
now.  The file split helper only handles page cache folios, which hold
exactly folio_nr_pages() references.

Rename folio_cache_ref_count() to folio_swapcache_ref_count() and drop the
anon check so the helper counts what its name says.  The file split helper
now uses folio_nr_pages() directly.

No feature change.

Link: https://lore.kernel.org/20260923-swap-thp-cleanup-v6-16-ba1b4ba72c6f@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Nico Pache <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Barry Song <baohua@kernel.org>
Cc: Youngjun Park <youngjun.park@lge.com>
Cc: Shivam Kalra <shivamkalra98@zohomail.in>
Cc: Kairui Song <ryncsn@gmail.com>
---

 mm/huge_memory.c |   35 +++++++++++++++--------------------
 1 file changed, 15 insertions(+), 20 deletions(-)

--- a/mm/huge_memory.c~mm-huge_memory-count-only-swap-cache-refs-in-anon-folio-split
+++ a/mm/huge_memory.c
@@ -3997,10 +3997,10 @@ int folio_check_splittable(struct folio
 	return 0;
 }
 
-/* Number of folio references from the pagecache or the swapcache. */
-static unsigned int folio_cache_ref_count(const struct folio *folio)
+/* Number of folio references from the swapcache. */
+static unsigned int folio_swapcache_ref_count(const struct folio *folio)
 {
-	if (folio_test_anon(folio) && !folio_test_swapcache(folio))
+	if (!folio_test_swapcache(folio))
 		return 0;
 	return folio_nr_pages(folio);
 }
@@ -4067,7 +4067,7 @@ static int __folio_freeze_split_anon(str
 
 	local_irq_disable();
 
-	if (!folio_ref_freeze(folio, folio_cache_ref_count(folio) + 1)) {
+	if (!folio_ref_freeze(folio, folio_swapcache_ref_count(folio) + 1)) {
 		ret = -EAGAIN;
 		goto out_no_split;
 	}
@@ -4104,7 +4104,7 @@ static int __folio_freeze_split_anon(str
 		next = folio_next(new_folio);
 		zone_device_private_split_cb(folio, new_folio);
 		folio_ref_unfreeze(new_folio,
-				   folio_cache_ref_count(new_folio) + 1);
+				   folio_swapcache_ref_count(new_folio) + 1);
 		if (do_lru)
 			lru_add_split_folio(folio, new_folio, lruvec, list);
 		if (ci)
@@ -4112,7 +4112,7 @@ static int __folio_freeze_split_anon(str
 	}
 
 	zone_device_private_split_cb(folio, NULL);
-	folio_ref_unfreeze(folio, folio_cache_ref_count(folio) + 1);
+	folio_ref_unfreeze(folio, folio_swapcache_ref_count(folio) + 1);
 
 	if (do_lru)
 		lruvec_unlock(lruvec);
@@ -4138,6 +4138,7 @@ static int __folio_freeze_split_file(str
 		unsigned int new_order, struct page *split_at,
 		struct list_head *list, enum split_type split_type)
 {
+	const long old_nr_pages = folio_nr_pages(folio);
 	struct address_space *mapping = folio->mapping;
 	XA_STATE(xas, &mapping->i_pages, folio->index);
 	struct folio *end_folio = folio_next(folio);
@@ -4211,22 +4212,16 @@ static int __folio_freeze_split_file(str
 		goto fail;
 	}
 
-	if (!folio_ref_freeze(folio, folio_cache_ref_count(folio) + 1)) {
+	if (!folio_ref_freeze(folio, old_nr_pages + 1)) {
 		ret = -EAGAIN;
 		goto fail;
 	}
 
-	if (folio_test_pmd_mappable(folio) &&
-	    new_order < HPAGE_PMD_ORDER) {
-		int nr = folio_nr_pages(folio);
-
-		if (folio_test_swapbacked(folio)) {
-			lruvec_stat_mod_folio(folio,
-					NR_SHMEM_THPS, -nr);
-		} else {
-			lruvec_stat_mod_folio(folio,
-					NR_FILE_THPS, -nr);
-		}
+	if (folio_test_pmd_mappable(folio) && new_order < HPAGE_PMD_ORDER) {
+		if (folio_test_swapbacked(folio))
+			lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -old_nr_pages);
+		else
+			lruvec_stat_mod_folio(folio, NR_FILE_THPS, -old_nr_pages);
 	}
 
 	/* lock lru list/PageCompound, ref frozen by page_ref_freeze */
@@ -4250,7 +4245,7 @@ static int __folio_freeze_split_file(str
 		next = folio_next(new_folio);
 
 		folio_ref_unfreeze(new_folio,
-				   folio_cache_ref_count(new_folio) + 1);
+				   folio_nr_pages(new_folio) + 1);
 
 		lru_add_split_folio(folio, new_folio, lruvec, list);
 
@@ -4277,7 +4272,7 @@ static int __folio_freeze_split_file(str
 	 * Otherwise, a parallel folio_try_get() can grab @folio
 	 * and its caller can see stale page cache entries.
 	 */
-	folio_ref_unfreeze(folio, folio_cache_ref_count(folio) + 1);
+	folio_ref_unfreeze(folio, folio_nr_pages(folio) + 1);
 	lruvec_unlock(lruvec);
 fail:
 	xas_unlock_irq(&xas);
_

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

mm-memcontrol-move-the-lru_zone_size-sanity-check-to-the-reader-side.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
mm-swap-fix-off-by-one-in-swap-cache-replace-sanity-check.patch
mm-huge_memory-fix-rejection-of-swap-cache-folios-with-a-mapping.patch
mm-huge_memory-invert-folio_ref_freeze-check-to-reduce-indentation.patch
mm-huge_memory-split-the-routine-for-splitting-anon-and-file-folio.patch
mm-huge_memory-rename-__split_unmapped_folio-to-__split_frozen_folio.patch
mm-huge_memory-consolidate-irq-and-locking-for-folio-split.patch
mm-huge_memory-move-eof-trimming-into-the-file-split-helper.patch
mm-huge_memory-move-unmap-and-remap-into-the-split-helpers.patch
mm-huge_memory-rename-remap_page-to-remap_anon_folio.patch
mm-huge_memory-move-the-racy-refcount-check-into-unmap_folio.patch
mm-huge_memory-move-filemap-management-into-the-file-split-helper.patch
mm-huge_memory-move-anon_vma-handling-into-the-anon-split-helper.patch
mm-huge_memory-move-memcg-switch-into-the-file-split-helper.patch
mm-huge_memory-drop-the-unused-do_lru-argument-of-the-file-split-helper.patch
mm-huge_memory-clean-up-after-split-folio-freeing-in-__folio_split.patch
mm-huge_memory-count-only-swap-cache-refs-in-anon-folio-split.patch
mm-huge_memory-drop-the-redundant-mapping-argument-of-__split_frozen_folio.patch