shmem: Convert shmem_unlock_mapping() to use filemap_get_folios()

This is a straightforward conversion.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>

mm/shmem.c

@@ -867,18 +867,17 @@ unsigned long shmem_swap_usage(struct vm_area_struct *vma)
  */
 void shmem_unlock_mapping(struct address_space *mapping)
 {
-	struct pagevec pvec;
+	struct folio_batch fbatch;
 	pgoff_t index = 0;
 
-	pagevec_init(&pvec);
+	folio_batch_init(&fbatch);
 	/*
 	 * Minor point, but we might as well stop if someone else SHM_LOCKs it.
 	 */
-	while (!mapping_unevictable(mapping)) {
-		if (!pagevec_lookup(&pvec, mapping, &index))
-			break;
-		check_move_unevictable_pages(&pvec);
-		pagevec_release(&pvec);
+	while (!mapping_unevictable(mapping) &&
+	       filemap_get_folios(mapping, &index, ~0UL, &fbatch)) {
+		check_move_unevictable_folios(&fbatch);
+		folio_batch_release(&fbatch);
 		cond_resched();
 	}
 }