Remove $FreeBSD$: two-line .h pattern

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

spdx: The BSD-3-Clause-FreeBSD identifier never was, drop -FreeBSD

There never was a BSD-3-Clause-FreeBSD SPDX identifier. Replace it
with BSD-3-Clause.

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

[skip ci] correct a few SPDX license tags

These were all incorrectly labeled as 2-clause BSD licenses by a
semi-automated process, when in fact they are 3-clause.

Discussed with: pfg, imp
MFC after: 2 weeks
Sponsored by: Axcient

Modernize geom_stats_snapshot_get

* A logically useless memset() is used to fault in some memory pages.
Change it to explicit_bzero so the compiler won't eliminate it.

* Eliminate the second memset. It made sense in the days of the Big
Kernel Lock, but not in the days of fine-grained SMP and especially
not in the days of VDSO.

MFC after: 2 weeks
Sponsored by: Axcient
Reviewed by: phk
Differential Revision: https://reviews.freebsd.org/D29047

Speed up geom_stats_resync in the presence of many devices

The old code had a O(n) loop, where n is the size of /dev/devstat.
Multiply that by another O(n) loop in devstat_mmap for a total of
O(n^2).

This change adds DIOCGMEDIASIZE support to /dev/devstat so userland can
quickly determine the right amount of memory to map, eliminating the
O(n) loop in userland.

This change decreases the time to run "gstat -bI0.001" with 16,384 md
devices from 29.7s to 4.2s.

Also, fix a memory leak first reported as PR 203097.

Sponsored by: Axcient
Reviewed by: mav, imp
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D28968

lib: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using mis-identified 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.

Remove getpagesize(3) error checking added in r317312

getpagesize(3) no longer fails as of r317436.

MFC after: 3 days
Sponsored by: Dell EMC Isilon

Fix type for `pagesize` to match the return type for getpagesize(3)
to fix the build

MFC after: 5 weeks
X-MFC with: r317311
Pointyhat to: ngie
Sponsored by: Dell EMC Isilon

Check for failures from getpagesize(3)

Return errno on failure, similar to the open(2) call above it.

MFC after: 5 weeks
Reported by: Coverity
CID: 1193753
Sponsored by: Dell EMC Isilon

Minor style(9) fixups

Delete trailing whitespace and sort headers.

Leave libgeom.h's placement alone, per reasoning in r317289.

MFC after: 5 weeks
Sponsored by: Dell EMC Isilon

Explicitly specify MAP_SHARED when mapping the stats file descriptor.

Reviewed by: kib
MFC after: 1 week

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

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

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

Use devstat instead of GEOM private statistics structure.

Leak more stuff into libgeom.

Add libgeom to the system.

Initially this only contains the functions for accessing the I/O
statistics data.