proc: convert smaps_account() to use a folio

Replace seven calls to compound_head() with one.

Link: https://lkml.kernel.org/r/20240402201252.917342-3-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/proc/task_mmu.c

@@ -444,6 +444,7 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
 		bool compound, bool young, bool dirty, bool locked,
 		bool migration)
 {
+	struct folio *folio = page_folio(page);
 	int i, nr = compound ? compound_nr(page) : 1;
 	unsigned long size = nr * PAGE_SIZE;
 
@@ -451,27 +452,28 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
 	 * First accumulate quantities that depend only on |size| and the type
 	 * of the compound page.
 	 */
-	if (PageAnon(page)) {
+	if (folio_test_anon(folio)) {
 		mss->anonymous += size;
-		if (!PageSwapBacked(page) && !dirty && !PageDirty(page))
+		if (!folio_test_swapbacked(folio) && !dirty &&
+		    !folio_test_dirty(folio))
 			mss->lazyfree += size;
 	}
 
-	if (PageKsm(page))
+	if (folio_test_ksm(folio))
 		mss->ksm += size;
 
 	mss->resident += size;
 	/* Accumulate the size in pages that have been accessed. */
-	if (young || page_is_young(page) || PageReferenced(page))
+	if (young || folio_test_young(folio) || folio_test_referenced(folio))
 		mss->referenced += size;
 
 	/*
 	 * Then accumulate quantities that may depend on sharing, or that may
 	 * differ page-by-page.
 	 *
-	 * page_count(page) == 1 guarantees the page is mapped exactly once.
+	 * refcount == 1 guarantees the page is mapped exactly once.
 	 * If any subpage of the compound page mapped with PTE it would elevate
-	 * page_count().
+	 * the refcount.
 	 *
 	 * The page_mapcount() is called to get a snapshot of the mapcount.
 	 * Without holding the page lock this snapshot can be slightly wrong as
@@ -480,7 +482,7 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
 	 * especially for migration entries.  Treat regular migration entries
 	 * as mapcount == 1.
 	 */
-	if ((page_count(page) == 1) || migration) {
+	if ((folio_ref_count(folio) == 1) || migration) {
 		smaps_page_accumulate(mss, page, size, size << PSS_SHIFT, dirty,
 			locked, true);
 		return;