[PATCH v4 1/9] mm/ksm: add ksm_get_folio

[alexs@xxxxxxxxxx]

From: "Alex Shi (tencent)" <alexs@xxxxxxxxxx>

The ksm only contains single pages, so we could add a new func
ksm_get_folio for get_ksm_page to use folio instead of pages to save a
couple of compound_head calls.

After all caller replaced, get_ksm_page will be removed.

Signed-off-by: Alex Shi (tencent) <alexs@xxxxxxxxxx>
To: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Izik Eidus <izik.eidus@xxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Chris Wright <chrisw@xxxxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
---
 mm/ksm.c | 40 ++++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 8c001819cf10..ac080235b002 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -915,10 +915,10 @@ enum get_ksm_page_flags {
  * a page to put something that might look like our key in page->mapping.
  * is on its way to being freed; but it is an anomaly to bear in mind.
  */
-static struct page *get_ksm_page(struct ksm_stable_node *stable_node,
+static struct folio *ksm_get_folio(struct ksm_stable_node *stable_node,
 				 enum get_ksm_page_flags flags)
 {
-	struct page *page;
+	struct folio *folio;
 	void *expected_mapping;
 	unsigned long kpfn;
 
@@ -926,8 +926,8 @@ static struct page *get_ksm_page(struct ksm_stable_node *stable_node,
 					PAGE_MAPPING_KSM);
 again:
 	kpfn = READ_ONCE(stable_node->kpfn); /* Address dependency. */
-	page = pfn_to_page(kpfn);
-	if (READ_ONCE(page->mapping) != expected_mapping)
+	folio = pfn_folio(kpfn);
+	if (READ_ONCE(folio->mapping) != expected_mapping)
 		goto stale;
 
 	/*
@@ -940,41 +940,41 @@ static struct page *get_ksm_page(struct ksm_stable_node *stable_node,
 	 * in folio_migrate_mapping(), it might still be our page,
 	 * in which case it's essential to keep the node.
 	 */
-	while (!get_page_unless_zero(page)) {
+	while (!folio_try_get(folio)) {
 		/*
 		 * Another check for page->mapping != expected_mapping would
 		 * work here too.  We have chosen the !PageSwapCache test to
 		 * optimize the common case, when the page is or is about to
 		 * be freed: PageSwapCache is cleared (under spin_lock_irq)
 		 * in the ref_freeze section of __remove_mapping(); but Anon
-		 * page->mapping reset to NULL later, in free_pages_prepare().
+		 * folio->mapping reset to NULL later, in free_pages_prepare().
 		 */
-		if (!PageSwapCache(page))
+		if (!folio_test_swapcache(folio))
 			goto stale;
 		cpu_relax();
 	}
 
-	if (READ_ONCE(page->mapping) != expected_mapping) {
-		put_page(page);
+	if (READ_ONCE(folio->mapping) != expected_mapping) {
+		folio_put(folio);
 		goto stale;
 	}
 
 	if (flags == GET_KSM_PAGE_TRYLOCK) {
-		if (!trylock_page(page)) {
-			put_page(page);
+		if (!folio_trylock(folio)) {
+			folio_put(folio);
 			return ERR_PTR(-EBUSY);
 		}
 	} else if (flags == GET_KSM_PAGE_LOCK)
-		lock_page(page);
+		folio_lock(folio);
 
 	if (flags != GET_KSM_PAGE_NOLOCK) {
-		if (READ_ONCE(page->mapping) != expected_mapping) {
-			unlock_page(page);
-			put_page(page);
+		if (READ_ONCE(folio->mapping) != expected_mapping) {
+			folio_unlock(folio);
+			folio_put(folio);
 			goto stale;
 		}
 	}
-	return page;
+	return folio;
 
 stale:
 	/*
@@ -990,6 +990,14 @@ static struct page *get_ksm_page(struct ksm_stable_node *stable_node,
 	return NULL;
 }
 
+static struct page *get_ksm_page(struct ksm_stable_node *stable_node,
+				 enum get_ksm_page_flags flags)
+{
+	struct folio *folio = ksm_get_folio(stable_node, flags);
+
+	return &folio->page;
+}
+
 /*
  * Removing rmap_item from stable or unstable tree.
  * This function will clean the information from the stable/unstable tree.
-- 
2.43.0