loader: implement map-vdisk and unmap-vdisk commands


loader: implement map-vdisk and unmap-vdisk commands

illumos update: https://www.illumos.org/issues/10598

Add map-vdisk and unmap-vdisk commands to create virtual disk interface on top of file. This will allow to use disk image from file system to load and start the kernel.

By mapping file, we create vdiskX device, the device will be listed by lsdev [-v] and can be accessed directly as ls vdisk0p1:/path or can be used as value for currdev variable.

vdisk strategy function does not use bcache as we have bcache used with backing file. vdisk can be unmapped when all consumers have closed the open files.

In first iteration we do not support the zfs images because zfs pools do keep the device open (there is no "zpool export" mechanism). Adding zfs support is relatively simple, we just need to run zfs disk probe after mapping is done.

Differential Revision: https://reviews.freebsd.org/D19733


tsoomeApr 26 2019, 5:58 PM
Differential Revision
D19733: loader: implement map-vdisk and unmap-vdisk commands
rS346758: MFC r345656: Do not map small IOCTL buffers to KVA, but copy.