f2fs: recover fallocated space

If a fallocated file is fsynced, we should recover the i_size after sudden
power cut.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -682,6 +682,7 @@ static int expand_inode_data(struct inode *inode, loff_t offset,
 		i_size_read(inode) < new_size) {
 		i_size_write(inode, new_size);
 		mark_inode_dirty(inode);
+		f2fs_write_inode(inode, NULL);
 	}
 
 	return ret;