By using FALLOC_FL_KEEP_SIZE in ->fallocate of f2fs, we can fallocate block past
EOF without changing i_size of inode. These blocks past EOF will not be
truncated in ->setattr as we truncate them only when change the file size.

We should give a chance to truncate blocks out of filesize in setattr().
Signed-off-by: NChao Yu <chao2.yu@samsung.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>