ToDo/Notes:
- Find and fix bugs.
- In between ntfs_prepare/commit_write, need exclusion between
simultaneous file extensions. This is given to us by holding i_sem
on the inode. The only places in the kernel when a file is resized
are prepare/commit write and truncate for both of which i_sem is
held. Just have to be careful in readpage/writepage and all other
helpers not running under i_sem that we play nice...
Also need to be careful with initialized_size extention in
ntfs_prepare_write. Basically, just be _very_ careful in this code...
UPDATE: The only things that need to be checked are read/writepage
which do not hold i_sem. Note writepage cannot change i_size but it
needs to cope with a concurrent i_size change, just like readpage.
Also both need to cope with concurrent changes to the other sizes,
i.e. initialized/allocated/compressed size, as well.
- Implement mft.c::sync_mft_mirror_umount(). We currently will just
leave the volume dirty on umoun
