ext4: fix fast commit may miss tracking range for FALLOC_FL_ZERO_RANGE

when call falloc with FALLOC_FL_ZERO_RANGE, to set an range to unwritten,
which has been already initialized. If the range is align to blocksize,
fast commit will not track range for this change.

Also track range for unwritten range in ext4_map_blocks().

Signed-off-by: Xin Yin <yinxin.x@bytedance.com>
Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20211221022839.374606-1-yinxin.x@bytedance.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

fs/ext4/extents.c

@@ -4647,8 +4647,6 @@ static long ext4_zero_range(struct file *file, loff_t offset,
 	ret = ext4_mark_inode_dirty(handle, inode);
 	if (unlikely(ret))
 		goto out_handle;
-	ext4_fc_track_range(handle, inode, offset >> inode->i_sb->s_blocksize_bits,
-			(offset + len - 1) >> inode->i_sb->s_blocksize_bits);
 	/* Zero out partial block at the edges of the range */
 	ret = ext4_zero_partial_blocks(handle, inode, offset, len);
 	if (ret >= 0)

fs/ext4/inode.c

@@ -741,10 +741,11 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
 			if (ret)
 				return ret;
 		}
-		ext4_fc_track_range(handle, inode, map->m_lblk,
-			    map->m_lblk + map->m_len - 1);
 	}
-
+	if (retval > 0 && (map->m_flags & EXT4_MAP_UNWRITTEN ||
+				map->m_flags & EXT4_MAP_MAPPED))
+		ext4_fc_track_range(handle, inode, map->m_lblk,
+					map->m_lblk + map->m_len - 1);
 	if (retval < 0)
 		ext_debug(inode, "failed with err %d\n", retval);
 	return retval;