sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

sys/geom: adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Implement automatic live resize support for GEOM MULTIPATH class.

In "manual" mode just automatically resize provider in any direction.
In "automatic" mode allow only growth (with new metadata write); in case
of shrinking destroy the multipath device same as before since it may be
undesirable to write new metadata within old user area.

MFC after: 1 month

Major GEOM MULTIPATH class rewrite:
- Improved locking and destruction process to fix crashes.
- Improved "automatic" configuration method to make it consistent and safe
by reading metadata back from all specified paths after writing to one.
- Added provider size check to reduce chance of ordering conflict with
other GEOM classes.
- Added "manual" configuration method without using on-disk metadata.
- Added "add" and "remove" commands to allow manage paths manually.
- Failed paths are no longer dropped from geom, but only marked as FAIL
and excluded from I/O operations.
- Automatically restore failed paths when all others paths are marked
as failed, for example, because of device-caused (not transport) errors.
- Added "fail" and "restore" commands to manually control FAIL flag.
- geom is now destroyed on last path disconnection.
- Added optional Active/Active mode support. Unlike Active/Passive
mode, load evenly distributed between all working paths. If supported by
the device, it allows to significantly improve performance, utilizing
bandwidth of all paths. It is controlled by -A option during creation.
Disabled by default now.
- Improved `status` and `list` commands output.

Sponsored by: iXsystems, inc.
MFC after: 1 month

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

- Import the HEAD csup code which is the basis for the cvsmode work.

First cut at GEOM based multipath. This is an active/passive{/passive...}
arrangement that has no intrinsic internal knowledge of whether devices
it is given are truly multipath devices. As such, this is a simplistic
approach, but still a useful one.

The basic approach is to (at present- this will change soon) use camcontrol
to find likely identical devices and and label the trailing sector of the
first one. This label contains both a full UUID and a name. The name is
what is presented in /dev/multipath, but the UUID is used as a true
distinguishor at g_taste time, thus making sure we don't have chaos
on a shared SAN where everyone names their data multipath as "Fred".

The first of N identical devices (and N *may* be 1!) becomes the active
path until a BIO request is failed with EIO or ENXIO. When this occurs,
the active disk is ripped away and the next in a list is picked to
(retry and) continue with.

During g_taste events new disks that meet the match criteria for existing
multipath geoms get added to the tail end of the list.

Thus, this active/passive setup actually does work for devices which
go away and come back, as do (now) mpt(4) and isp(4) SAN based disks.

There is still a lot to do to improve this- like about 5 of the 12
recommendations I've received about it, but it's been functional enough
for a while that it deserves a broader test base.

Reviewed by: pjd
Sponsored by: IronPort Systems
MFC: 2 months