[PATCH 05/10] mm/ksm: use folio in stable_tree_search

[alexs@kernel.org]

From: "Alex Shi (tencent)" <alexs@kernel.org>

The stable_tree_search() function is actually using folio internal, just
pass the folio parameter from cmp_and_merge_page().

And in cmp_and_merge_page(), the parameter 'page' is actually a folio
too, so use folio to save a few compound check in necessnary context.

Signed-off-by: Alex Shi (tencent) <alexs@kernel.org>
---
 mm/ksm.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 2e4790842515..f68779651841 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1825,7 +1825,7 @@ static __always_inline struct folio *chain(struct ksm_stable_node **s_n_d,
  * This function returns the stable tree node of identical content if found,
  * NULL otherwise.
  */
-static struct page *stable_tree_search(struct page *page)
+static struct folio *stable_tree_search(struct folio *folio)
 {
 	int nid;
 	struct rb_root *root;
@@ -1833,14 +1833,12 @@ static struct page *stable_tree_search(struct page *page)
 	struct rb_node *parent;
 	struct ksm_stable_node *stable_node, *stable_node_dup, *stable_node_any;
 	struct ksm_stable_node *page_node;
-	struct folio *folio;
 
-	folio = page_folio(page);
 	page_node = folio_stable_node(folio);
 	if (page_node && page_node->head != &migrate_nodes) {
 		/* ksm page forked */
 		folio_get(folio);
-		return &folio->page;
+		return folio;
 	}
 
 	nid = get_kpfn_nid(folio_pfn(folio));
@@ -1907,7 +1905,7 @@ static struct page *stable_tree_search(struct page *page)
 			goto again;
 		}
 
-		ret = memcmp_pages(page, &tree_folio->page);
+		ret = memcmp_pages(folio_page(folio, 0), &tree_folio->page);
 		folio_put(tree_folio);
 
 		parent = *new;
@@ -1973,7 +1971,7 @@ static struct page *stable_tree_search(struct page *page)
 				folio_put(tree_folio);
 				goto replace;
 			}
-			return &tree_folio->page;
+			return tree_folio;
 		}
 	}
 
@@ -1987,7 +1985,7 @@ static struct page *stable_tree_search(struct page *page)
 out:
 	if (is_page_sharing_candidate(page_node)) {
 		folio_get(folio);
-		return &folio->page;
+		return folio;
 	} else
 		return NULL;
 
@@ -2037,7 +2035,7 @@ static struct page *stable_tree_search(struct page *page)
 	}
 	stable_node_dup->head = &migrate_nodes;
 	list_add(&stable_node_dup->list, stable_node_dup->head);
-	return &folio->page;
+	return folio;
 
 chain_append:
 	/* stable_node_dup could be null if it reached the limit */
@@ -2324,6 +2322,7 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
 	unsigned int checksum;
 	int err;
 	bool max_page_sharing_bypass = false;
+	struct folio *folio, *kfolio;
 
 	stable_node = page_stable_node(page);
 	if (stable_node) {
@@ -2346,30 +2345,31 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
 	}
 
 	/* We first start with searching the page inside the stable tree */
-	kpage = stable_tree_search(page);
-	if (kpage == page && rmap_item->head == stable_node) {
-		put_page(kpage);
+	folio = page_folio(page);
+	kfolio = stable_tree_search(folio);
+	if (kfolio == folio && rmap_item->head == stable_node) {
+		folio_put(kfolio);
 		return;
 	}
 
 	remove_rmap_item_from_tree(rmap_item);
 
-	if (kpage) {
-		if (PTR_ERR(kpage) == -EBUSY)
+	if (kfolio) {
+		if (kfolio == ERR_PTR(-EBUSY))
 			return;
 
-		err = try_to_merge_with_ksm_page(rmap_item, page, kpage);
+		err = try_to_merge_with_ksm_page(rmap_item, page, folio_page(kfolio, 0));
 		if (!err) {
 			/*
 			 * The page was successfully merged:
 			 * add its rmap_item to the stable tree.
 			 */
-			lock_page(kpage);
-			stable_tree_append(rmap_item, page_stable_node(kpage),
+			folio_lock(kfolio);
+			stable_tree_append(rmap_item, folio_stable_node(kfolio),
 					   max_page_sharing_bypass);
-			unlock_page(kpage);
+			folio_unlock(kfolio);
 		}
-		put_page(kpage);
+		folio_put(kfolio);
 		return;
 	}
 
-- 
2.43.0