[CRIU] [RFC PATCH 0/5] Autofs migration support

[Stanislav Kinsburskiy]

This patch set is a proof of concept.
It does the following to migrate AutoFS:

1) Introduces "dump" callback to fix mount option "pgrp=". It is pid namespace
dependent, but mounts are colleted in init pid.
2) Introduced new fstype "mount" callback, becuase AutoFS "timeout=" option
have to be removed, while timeout itself have to be set via ioctl.
3) Introduced "post_open" callback for pipes to set real AutoFS mount point
owner and pass proper pipe end to kernel.
4) Brings auto_dev-ioctl.h header for easy ioctl calls.
5) Creates target dentry for mounts, if nested to AutoFS mount.