ext4: rename and improbe ext4_es_find_extent()

This commit renames ext4_es_find_extent with ext4_es_find_delayed_extent
and improve this function.  First, we split input and output parameter.
Second, this function never return the first block of the next delayed
extent after 'es'.

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Jan kara <jack@suse.cz>
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 2df9354..7e85a10 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -464,8 +464,7 @@
 		 * If there is a delay extent at this offset,
 		 * it will be as a data.
 		 */
-		es.es_lblk = last;
-		(void)ext4_es_find_extent(inode, &es);
+		ext4_es_find_delayed_extent(inode, last, &es);
 		if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
 			if (last != start)
 				dataoff = last << blkbits;
@@ -548,8 +547,7 @@
 		 * If there is a delay extent at this offset,
 		 * we will skip this extent.
 		 */
-		es.es_lblk = last;
-		(void)ext4_es_find_extent(inode, &es);
+		ext4_es_find_delayed_extent(inode, last, &es);
 		if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
 			last = es.es_lblk + es.es_len;
 			holeoff = last << blkbits;