Rewrite the file operations to utilize the iomap infrastructure,
replacing the legacy buffer-head based implementation.
Implement ntfs_setattr() with size change handling, uid/gid/mode.
Add support for Direct I/O.
Add support for fallocate with the FALLOC_FL_KEEP_SIZE,
FALLOC_FL_PUNCH_HOLE, FALLOC_FL_COLLAPSE_RANGE, FALLOC_FL_INSERT_RANGE
and FALLOC_FL_ALLOCATE_RANGE modes.
Implement .llseek with SEEK_DATA / SEEK_HOLE support.