ClearFd clears the loop device associated with filedescriptor fd.

ClearFdFile clears the loop device "devicename".

CtlGetFree finds a free loop device querying the loop control device pointed by fd.

FindDevice finds an unused loop device.

New initializes a Loop struct and allocates a loodevice to it.

SetFd associates a loop device pointed by lfd with a regular file pointed by ffd.

SetFdFiles associates loop device "devicename" with regular file "filename".

/dev/loop-control interface */.

* IOCTL commands --- we will commandeer 0x4C ('L') */.

Loop implements mount.Mount.