Add FreeBSD support to OpenZFS

Add the FreeBSD platform code to the OpenZFS repository.  As of this
commit the source can be compiled and tested on FreeBSD 11 and 12.
Subsequent commits are now required to compile on FreeBSD and Linux.
Additionally, they must pass the ZFS Test Suite on FreeBSD which is
being run by the CI.  As of this commit 1230 tests pass on FreeBSD
and there are no unexpected failures.

Reviewed-by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Co-authored-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #898 
Closes #8987

tests/zfs-tests/include/libtest.shlib

@@ -4056,13 +4056,19 @@ function ls_xattr # path
 
 function get_arcstat # stat
 {
-	if is_linux; then
-		typeset stat=$1
+	typeset stat=$1
+
+	case $(uname) in
+	FreeBSD)
+		sysctl -n kstat.zfs.misc.arcstats.$stat
+		;;
+	Linux)
 		typeset zfs_arcstats="/proc/spl/kstat/zfs/arcstats"
 		[[ -f "$zfs_arcstats" ]] || return 1
 		grep $stat $zfs_arcstats | awk '{print $3}'
-		return $?
-	else
-		return 1
-	fi
+		;;
+	*)
+		false
+		;;
+	esac
 }

tests/zfs-tests/include/tunables.cfg

@@ -36,8 +36,8 @@ INITIALIZE_CHUNK_SIZE		initialize_chunk_size		zfs_initialize_chunk_size
 INITIALIZE_VALUE		initialize_value		zfs_initialize_value
 KEEP_LOG_SPACEMAPS_AT_EXPORT	keep_log_spacemaps_at_export	zfs_keep_log_spacemaps_at_export
 L2ARC_NOPREFETCH		l2arc.noprefetch		l2arc_noprefetch
-L2ARC_REBUILD_BLOCKS_MIN_L2SIZE	UNSUPPORTED			l2arc_rebuild_blocks_min_l2size
-L2ARC_REBUILD_ENABLED		UNSUPPORTED			l2arc_rebuild_enabled
+L2ARC_REBUILD_BLOCKS_MIN_L2SIZE	l2arc.rebuild_blocks_min_l2size	l2arc_rebuild_blocks_min_l2size
+L2ARC_REBUILD_ENABLED		l2arc.rebuild_enabled		l2arc_rebuild_enabled
 L2ARC_WRITE_BOOST		l2arc.write_boost		l2arc_write_boost
 L2ARC_WRITE_MAX			l2arc.write_max			l2arc_write_max
 LIVELIST_CONDENSE_NEW_ALLOC	livelist.condense.new_alloc	zfs_livelist_condense_new_alloc

tests/zfs-tests/tests/functional/cli_root/zpool_import/zpool_import_missing_003_pos.ksh

@@ -59,8 +59,8 @@
 
 verify_runnable "global"
 
-# See issue: https://github.com/zfsonlinux/zfs/issues/6839
-if is_linux; then
+# See issue: https://github.com/openzfs/zfs/issues/6839
+if ! is_illumos; then
 	log_unsupported "Test case may be slow"
 fi