+ ksm-use-a-folio-inside-cmp_and_merge_page.patch added to mm-new branch

+ ksm-use-a-folio-inside-cmp_and_merge_page.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: ksm: use a folio inside cmp_and_merge_page()
has been added to the -mm mm-new branch.  Its filename is
     ksm-use-a-folio-inside-cmp_and_merge_page.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ksm-use-a-folio-inside-cmp_and_merge_page.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
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: ksm: use a folio inside cmp_and_merge_page()
Date: Tue, 16 Sep 2025 19:11:59 +0100

This removes the last call to page_stable_node(), so delete the wrapper. 
It also removes a call to trylock_page() and saves a call to
compound_head(), as well as removing a reference to folio->page.

Link: https://lkml.kernel.org/r/20250916181219.2400258-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Longlong Xia <xialonglong@kylinos.cn>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/ksm.c |   15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

--- a/mm/ksm.c~ksm-use-a-folio-inside-cmp_and_merge_page
+++ a/mm/ksm.c
@@ -1061,11 +1061,6 @@ struct ksm_stable_node *folio_stable_nod
 	return folio_test_ksm(folio) ? folio_raw_mapping(folio) : NULL;
 }
 
-static inline struct ksm_stable_node *page_stable_node(struct page *page)
-{
-	return folio_stable_node(page_folio(page));
-}
-
 static inline void folio_set_stable_node(struct folio *folio,
 					 struct ksm_stable_node *stable_node)
 {
@@ -2225,6 +2220,7 @@ static void stable_tree_append(struct ks
  */
 static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_item)
 {
+	struct folio *folio = page_folio(page);
 	struct ksm_rmap_item *tree_rmap_item;
 	struct page *tree_page = NULL;
 	struct ksm_stable_node *stable_node;
@@ -2233,7 +2229,7 @@ static void cmp_and_merge_page(struct pa
 	int err;
 	bool max_page_sharing_bypass = false;
 
-	stable_node = page_stable_node(page);
+	stable_node = folio_stable_node(folio);
 	if (stable_node) {
 		if (stable_node->head != &migrate_nodes &&
 		    get_kpfn_nid(READ_ONCE(stable_node->kpfn)) !=
@@ -2272,7 +2268,7 @@ static void cmp_and_merge_page(struct pa
 
 	/* Start by searching for the folio in the stable tree */
 	kfolio = stable_tree_search(page);
-	if (&kfolio->page == page && rmap_item->head == stable_node) {
+	if (kfolio == folio && rmap_item->head == stable_node) {
 		folio_put(kfolio);
 		return;
 	}
@@ -2353,10 +2349,11 @@ static void cmp_and_merge_page(struct pa
 			 * the page is locked, it is better to skip it and
 			 * perhaps try again later.
 			 */
-			if (!trylock_page(page))
+			if (!folio_trylock(folio))
 				return;
 			split_huge_page(page);
-			unlock_page(page);
+			folio = page_folio(page);
+			folio_unlock(folio);
 		}
 	}
 }
_

Patches currently in -mm which might be from willy@infradead.org are

mm-remove-mlock_count-from-struct-page.patch
ptdesc-convert-__page_flags-to-pt_flags.patch
ptdesc-remove-references-to-folios-from-__pagetable_ctor-and-pagetable_dtor.patch
ptdesc-remove-ptdesc_to_virt.patch
mm-constify-compound_order-and-page_size.patch
mm-remove-redundant-test-in-validate_page_before_insert.patch
mm-remove-page-order.patch
ksm-use-a-folio-inside-cmp_and_merge_page.patch