mm: page_idle: convert page idle to use a folio

Firstly, make page_idle_get_page() return a folio, also rename it to
page_idle_get_folio(), then, use it to convert page_idle_bitmap_read() and
page_idle_bitmap_write() functions.

Link: https://lkml.kernel.org/r/20221230070849.63358-3-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_idle.c

@@ -31,19 +31,22 @@
  *
  * This function tries to get a user memory page by pfn as described above.
  */
-static struct page *page_idle_get_page(unsigned long pfn)
+static struct folio *page_idle_get_folio(unsigned long pfn)
 {
 	struct page *page = pfn_to_online_page(pfn);
+	struct folio *folio;
 
-	if (!page || !PageLRU(page) ||
-	    !get_page_unless_zero(page))
+	if (!page || PageTail(page))
 		return NULL;
 
-	if (unlikely(!PageLRU(page))) {
-		put_page(page);
-		page = NULL;
+	folio = page_folio(page);
+	if (!folio_test_lru(folio) || !folio_try_get(folio))
+		return NULL;
+	if (unlikely(page_folio(page) != folio || !folio_test_lru(folio))) {
+		folio_put(folio);
+		folio = NULL;
 	}
-	return page;
+	return folio;
 }
 
 static bool page_idle_clear_pte_refs_one(struct folio *folio,
@@ -83,10 +86,8 @@ static bool page_idle_clear_pte_refs_one(struct folio *folio,
 	return true;
 }
 
-static void page_idle_clear_pte_refs(struct page *page)
+static void page_idle_clear_pte_refs(struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
-
 	/*
 	 * Since rwc.try_lock is unused, rwc is effectively immutable, so we
 	 * can make it static to save some cycles and stack.
@@ -115,7 +116,7 @@ static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
 				     loff_t pos, size_t count)
 {
 	u64 *out = (u64 *)buf;
-	struct page *page;
+	struct folio *folio;
 	unsigned long pfn, end_pfn;
 	int bit;
 
@@ -134,19 +135,19 @@ static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
 		bit = pfn % BITMAP_CHUNK_BITS;
 		if (!bit)
 			*out = 0ULL;
-		page = page_idle_get_page(pfn);
-		if (page) {
-			if (page_is_idle(page)) {
+		folio = page_idle_get_folio(pfn);
+		if (folio) {
+			if (folio_test_idle(folio)) {
 				/*
 				 * The page might have been referenced via a
 				 * pte, in which case it is not idle. Clear
 				 * refs and recheck.
 				 */
-				page_idle_clear_pte_refs(page);
-				if (page_is_idle(page))
+				page_idle_clear_pte_refs(folio);
+				if (folio_test_idle(folio))
 					*out |= 1ULL << bit;
 			}
-			put_page(page);
+			folio_put(folio);
 		}
 		if (bit == BITMAP_CHUNK_BITS - 1)
 			out++;
@@ -160,7 +161,7 @@ static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
 				      loff_t pos, size_t count)
 {
 	const u64 *in = (u64 *)buf;
-	struct page *page;
+	struct folio *folio;
 	unsigned long pfn, end_pfn;
 	int bit;
 
@@ -178,11 +179,11 @@ static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
 	for (; pfn < end_pfn; pfn++) {
 		bit = pfn % BITMAP_CHUNK_BITS;
 		if ((*in >> bit) & 1) {
-			page = page_idle_get_page(pfn);
-			if (page) {
-				page_idle_clear_pte_refs(page);
-				set_page_idle(page);
-				put_page(page);
+			folio = page_idle_get_folio(pfn);
+			if (folio) {
+				page_idle_clear_pte_refs(folio);
+				folio_set_idle(folio);
+				folio_put(folio);
 			}
 		}
 		if (bit == BITMAP_CHUNK_BITS - 1)