[RFC]swapfso and "ioctl" function for filesystems

[phcoder <phcoder@gmail.com>]

Hello, all.
For some FS sometimes additional functions are needed. It could be some
type of control (e.g. in ZFS manage zpools) or preparation for OS
booting (e.g. in FAT put IO.SYS and MSDOS.SYS at the begining of the
root directory). While theese functions are quite specific to FS
sometimes are important to implement. So I suggest to add to grub_fs a
pointer to an array in which fs module can put custom functions.
Also in many filesystems it's quite difficult to add a new file or
remove already existing one it's often quite easy to exchange 2 files or
directories. So I intend to implement a call "swapfso" (FSO=File System
Object) at least for fat and ext2. Such a call could be useful to have
multiple OS on the same partition or to have multiple configurations of
the same OS (e.g. normal and backup). Then I think to have this function
in this extended list (even if this function can be implemented for more
FS) unless maintainers suggest that such function should be a part of
grub_fs. In this case a good idea would be to have 2 modules for
fat,ext2,...: one with swapfso and one without for core image.
Vladimir 'phcoder' Serbinenko