ext4: let ext4_ext_map_blocks return EXT4_MAP_UNWRITTEN flag

This commit lets ext4_ext_map_blocks return EXT4_MAP_UNWRITTEN flag
because in later commit ext4_map_blocks needs to use this flag to
determine the extent status.

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 895c195..cae8ae3 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3659,6 +3659,7 @@
 			ext4_set_io_unwritten_flag(inode, io);
 		else
 			ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
+		map->m_flags |= EXT4_MAP_UNWRITTEN;
 		if (ext4_should_dioread_nolock(inode))
 			map->m_flags |= EXT4_MAP_UNINIT;
 		goto out;
@@ -3680,8 +3681,10 @@
 	 * repeat fallocate creation request
 	 * we already have an unwritten extent
 	 */
-	if (flags & EXT4_GET_BLOCKS_UNINIT_EXT)
+	if (flags & EXT4_GET_BLOCKS_UNINIT_EXT) {
+		map->m_flags |= EXT4_MAP_UNWRITTEN;
 		goto map_out;
+	}
 
 	/* buffered READ or buffered write_begin() lookup */
 	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
@@ -4111,6 +4114,7 @@
 	/* Mark uninitialized */
 	if (flags & EXT4_GET_BLOCKS_UNINIT_EXT){
 		ext4_ext_mark_uninitialized(&newex);
+		map->m_flags |= EXT4_MAP_UNWRITTEN;
 		/*
 		 * io_end structure was created for every IO write to an
 		 * uninitialized extent. To avoid unnecessary conversion,