diff --git a/fs/nilfs2/bmap.c b/fs/nilfs2/bmap.c
index 383f0afa2cea367f5da038ed4875c88cb97ea5e1..cd14ea25968cb0b817452141e0bdf734e913407a 100644
--- a/fs/nilfs2/bmap.c
+++ b/fs/nilfs2/bmap.c
@@ -450,15 +450,9 @@ int nilfs_bmap_test_and_clear_dirty(struct nilfs_bmap *bmap)
 __u64 nilfs_bmap_data_get_key(const struct nilfs_bmap *bmap,
 			      const struct buffer_head *bh)
 {
-	struct buffer_head *pbh;
-	__u64 key;
+	loff_t pos = folio_pos(bh->b_folio) + bh_offset(bh);
 
-	key = page_index(bh->b_page) << (PAGE_SHIFT -
-					 bmap->b_inode->i_blkbits);
-	for (pbh = page_buffers(bh->b_page); pbh != bh; pbh = pbh->b_this_page)
-		key++;
-
-	return key;
+	return pos >> bmap->b_inode->i_blkbits;
 }
 
 __u64 nilfs_bmap_find_target_seq(const struct nilfs_bmap *bmap, __u64 key)