btrfs: Convert btree_migratepage to migrate_folio

Use a folio throughout this function.  migrate_page() will be converted
later.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -952,28 +952,28 @@ void btrfs_submit_metadata_bio(struct inode *inode, struct bio *bio, int mirror_
 }
 
 #ifdef CONFIG_MIGRATION
-static int btree_migratepage(struct address_space *mapping,
-			struct page *newpage, struct page *page,
-			enum migrate_mode mode)
+static int btree_migrate_folio(struct address_space *mapping,
+		struct folio *dst, struct folio *src, enum migrate_mode mode)
 {
 	/*
 	 * we can't safely write a btree page from here,
 	 * we haven't done the locking hook
 	 */
-	if (PageDirty(page))
+	if (folio_test_dirty(src))
 		return -EAGAIN;
 	/*
 	 * Buffers may be managed in a filesystem specific way.
 	 * We must have no buffers or drop them.
 	 */
-	if (page_has_private(page) &&
-	    !try_to_release_page(page, GFP_KERNEL))
+	if (folio_get_private(src) &&
+	    !filemap_release_folio(src, GFP_KERNEL))
 		return -EAGAIN;
-	return migrate_page(mapping, newpage, page, mode);
+	return migrate_page(mapping, &dst->page, &src->page, mode);
 }
+#else
+#define btree_migrate_folio NULL
 #endif
 
-
 static int btree_writepages(struct address_space *mapping,
 			    struct writeback_control *wbc)
 {
@@ -1073,10 +1073,8 @@ static const struct address_space_operations btree_aops = {
 	.writepages	= btree_writepages,
 	.release_folio	= btree_release_folio,
 	.invalidate_folio = btree_invalidate_folio,
-#ifdef CONFIG_MIGRATION
-	.migratepage	= btree_migratepage,
-#endif
-	.dirty_folio = btree_dirty_folio,
+	.migrate_folio	= btree_migrate_folio,
+	.dirty_folio	= btree_dirty_folio,
 };
 
 struct extent_buffer *btrfs_find_create_tree_block(