mm: convert do_wp_page() to use a folio

Saves many calls to compound_head().

Link: https://lkml.kernel.org/r/20220902194653.1739778-42-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memory.c

@@ -3368,6 +3368,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf)
 {
 	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
 	struct vm_area_struct *vma = vmf->vma;
+	struct folio *folio;
 
 	VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE));
 	VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE));
@@ -3414,48 +3415,47 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf)
 	 * Take out anonymous pages first, anonymous shared vmas are
 	 * not dirty accountable.
 	 */
-	if (PageAnon(vmf->page)) {
-		struct page *page = vmf->page;
-
+	folio = page_folio(vmf->page);
+	if (folio_test_anon(folio)) {
 		/*
 		 * If the page is exclusive to this process we must reuse the
 		 * page without further checks.
 		 */
-		if (PageAnonExclusive(page))
+		if (PageAnonExclusive(vmf->page))
 			goto reuse;
 
 		/*
-		 * We have to verify under page lock: these early checks are
-		 * just an optimization to avoid locking the page and freeing
+		 * We have to verify under folio lock: these early checks are
+		 * just an optimization to avoid locking the folio and freeing
 		 * the swapcache if there is little hope that we can reuse.
 		 *
-		 * PageKsm() doesn't necessarily raise the page refcount.
+		 * KSM doesn't necessarily raise the folio refcount.
 		 */
-		if (PageKsm(page) || page_count(page) > 3)
+		if (folio_test_ksm(folio) || folio_ref_count(folio) > 3)
 			goto copy;
-		if (!PageLRU(page))
+		if (!folio_test_lru(folio))
 			/*
 			 * Note: We cannot easily detect+handle references from
-			 * remote LRU pagevecs or references to PageLRU() pages.
+			 * remote LRU pagevecs or references to LRU folios.
 			 */
 			lru_add_drain();
-		if (page_count(page) > 1 + PageSwapCache(page))
+		if (folio_ref_count(folio) > 1 + folio_test_swapcache(folio))
 			goto copy;
-		if (!trylock_page(page))
+		if (!folio_trylock(folio))
 			goto copy;
-		if (PageSwapCache(page))
-			try_to_free_swap(page);
-		if (PageKsm(page) || page_count(page) != 1) {
-			unlock_page(page);
+		if (folio_test_swapcache(folio))
+			folio_free_swap(folio);
+		if (folio_test_ksm(folio) || folio_ref_count(folio) != 1) {
+			folio_unlock(folio);
 			goto copy;
 		}
 		/*
-		 * Ok, we've got the only page reference from our mapping
-		 * and the page is locked, it's dark out, and we're wearing
+		 * Ok, we've got the only folio reference from our mapping
+		 * and the folio is locked, it's dark out, and we're wearing
 		 * sunglasses. Hit it.
 		 */
-		page_move_anon_rmap(page, vma);
-		unlock_page(page);
+		page_move_anon_rmap(vmf->page, vma);
+		folio_unlock(folio);
 reuse:
 		if (unlikely(unshare)) {
 			pte_unmap_unlock(vmf->pte, vmf->ptl);