page-writeback: convert write_cache_pages() to use filemap_get_folios_tag()

Convert function to use folios throughout.  This is in preparation for the
removal of find_get_pages_range_tag().  This change removes 8 calls to
compound_head(), and the function now supports large folios.

Link: https://lkml.kernel.org/r/20230104211448.4804-5-vishal.moola@gmail.comSigned-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcow (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page-writeback.c

@@ -2398,15 +2398,15 @@ int write_cache_pages(struct address_space *mapping,
 	int ret = 0;
 	int done = 0;
 	int error;
-	struct pagevec pvec;
-	int nr_pages;
+	struct folio_batch fbatch;
+	int nr_folios;
 	pgoff_t index;
 	pgoff_t end;		/* Inclusive */
 	pgoff_t done_index;
 	int range_whole = 0;
 	xa_mark_t tag;
 
-	pagevec_init(&pvec);
+	folio_batch_init(&fbatch);
 	if (wbc->range_cyclic) {
 		index = mapping->writeback_index; /* prev offset */
 		end = -1;
@@ -2426,17 +2426,18 @@ int write_cache_pages(struct address_space *mapping,
 	while (!done && (index <= end)) {
 		int i;
 
-		nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end,
-				tag);
-		if (nr_pages == 0)
+		nr_folios = filemap_get_folios_tag(mapping, &index, end,
+				tag, &fbatch);
+
+		if (nr_folios == 0)
 			break;
 
-		for (i = 0; i < nr_pages; i++) {
-			struct page *page = pvec.pages[i];
+		for (i = 0; i < nr_folios; i++) {
+			struct folio *folio = fbatch.folios[i];
 
-			done_index = page->index;
+			done_index = folio->index;
 
-			lock_page(page);
+			folio_lock(folio);
 
 			/*
 			 * Page truncated or invalidated. We can freely skip it
@@ -2446,30 +2447,30 @@ int write_cache_pages(struct address_space *mapping,
 			 * even if there is now a new, dirty page at the same
 			 * pagecache address.
 			 */
-			if (unlikely(page->mapping != mapping)) {
+			if (unlikely(folio->mapping != mapping)) {
 continue_unlock:
-				unlock_page(page);
+				folio_unlock(folio);
 				continue;
 			}
 
-			if (!PageDirty(page)) {
+			if (!folio_test_dirty(folio)) {
 				/* someone wrote it for us */
 				goto continue_unlock;
 			}
 
-			if (PageWriteback(page)) {
+			if (folio_test_writeback(folio)) {
 				if (wbc->sync_mode != WB_SYNC_NONE)
-					wait_on_page_writeback(page);
+					folio_wait_writeback(folio);
 				else
 					goto continue_unlock;
 			}
 
-			BUG_ON(PageWriteback(page));
-			if (!clear_page_dirty_for_io(page))
+			BUG_ON(folio_test_writeback(folio));
+			if (!folio_clear_dirty_for_io(folio))
 				goto continue_unlock;
 
 			trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
-			error = (*writepage)(page, wbc, data);
+			error = writepage(&folio->page, wbc, data);
 			if (unlikely(error)) {
 				/*
 				 * Handle errors according to the type of
@@ -2484,11 +2485,12 @@ int write_cache_pages(struct address_space *mapping,
 				 * the first error.
 				 */
 				if (error == AOP_WRITEPAGE_ACTIVATE) {
-					unlock_page(page);
+					folio_unlock(folio);
 					error = 0;
 				} else if (wbc->sync_mode != WB_SYNC_ALL) {
 					ret = error;
-					done_index = page->index + 1;
+					done_index = folio->index +
+						folio_nr_pages(folio);
 					done = 1;
 					break;
 				}
@@ -2508,7 +2510,7 @@ int write_cache_pages(struct address_space *mapping,
 				break;
 			}
 		}
-		pagevec_release(&pvec);
+		folio_batch_release(&fbatch);
 		cond_resched();
 	}