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

lib/libzfs/Makefile.am

@@ -27,6 +27,15 @@ USER_C = \
 	libzfs_status.c \
 	libzfs_util.c
 
+
+if BUILD_FREEBSD
+USER_C += \
+	os/freebsd/libzfs_fsshare.c \
+	os/freebsd/libzfs_compat.c \
+	os/freebsd/libzfs_ioctl_compat.c \
+	os/freebsd/libzfs_zmount.c
+endif
+
 if BUILD_LINUX
 USER_C += \
 	os/linux/libzfs_mount_os.c \
@@ -35,7 +44,6 @@ USER_C += \
 	os/linux/libzfs_util_os.c
 endif
 
-
 KERNEL_C = \
 	algs/sha2/sha2.c \
 	cityhash.c \
@@ -70,7 +78,12 @@ libzfs_la_LIBADD += \
 	$(top_builddir)/lib/libshare/libshare.la
 endif
 
+if BUILD_FREEBSD
+libzfs_la_LIBADD += -lutil -lgeom
+libzfs_la_LDFLAGS = -version-info 4:0:0
+else
 libzfs_la_LDFLAGS = -version-info 2:0:0
+endif
 
 libzfs_la_LIBADD += -lm $(LIBSSL)
 

lib/libzfs/libzfs_util.c

@@ -881,7 +881,7 @@ libzfs_init(void)
 		return (NULL);
 	}
 
-	if ((hdl->libzfs_fd = open(ZFS_DEV, O_RDWR)) < 0) {
+	if ((hdl->libzfs_fd = open(ZFS_DEV, O_RDWR|O_EXCL)) < 0) {
 		free(hdl);
 		return (NULL);
 	}

lib/libzfs/os/freebsd/libzfs_compat.c

@@ -0,0 +1,323 @@
+/*
+ * CDDL HEADER SART
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2013 Martin Matuska <mm@FreeBSD.org>. All rights reserved.
+ */
+#include <os/freebsd/zfs/sys/zfs_ioctl_compat.h>
+#include <libzfs_impl.h>
+#include <libzfs.h>
+#include <libzutil.h>
+#include <sys/sysctl.h>
+#include <libintl.h>
+#include <sys/linker.h>
+#include <sys/module.h>
+#include <sys/stat.h>
+#include <sys/param.h>
+
+int zfs_ioctl_version = ZFS_IOCVER_UNDEF;
+// static int zfs_spa_version = -1;
+
+void
+libzfs_set_pipe_max(int infd)
+{
+	/* FreeBSD automatically resizes */
+}
+
+static int
+execvPe(const char *name, const char *path, char * const *argv,
+    char * const *envp)
+{
+	const char **memp;
+	size_t cnt, lp, ln;
+	int eacces, save_errno;
+	char *cur, buf[MAXPATHLEN];
+	const char *p, *bp;
+	struct stat sb;
+
+	eacces = 0;
+
+	/* If it's an absolute or relative path name, it's easy. */
+	if (strchr(name, '/')) {
+		bp = name;
+		cur = NULL;
+		goto retry;
+	}
+	bp = buf;
+
+	/* If it's an empty path name, fail in the usual POSIX way. */
+	if (*name == '\0') {
+		errno = ENOENT;
+		return (-1);
+	}
+
+	cur = alloca(strlen(path) + 1);
+	if (cur == NULL) {
+		errno = ENOMEM;
+		return (-1);
+	}
+	strcpy(cur, path);
+	while ((p = strsep(&cur, ":")) != NULL) {
+		/*
+		 * It's a SHELL path -- double, leading and trailing colons
+		 * mean the current directory.
+		 */
+		if (*p == '\0') {
+			p = ".";
+			lp = 1;
+		} else
+			lp = strlen(p);
+		ln = strlen(name);
+
+		/*
+		 * If the path is too long complain.  This is a possible
+		 * security issue; given a way to make the path too long
+		 * the user may execute the wrong program.
+		 */
+		if (lp + ln + 2 > sizeof (buf)) {
+			(void) write(STDERR_FILENO, "execvP: ", 8);
+			(void) write(STDERR_FILENO, p, lp);
+			(void) write(STDERR_FILENO, ": path too long\n",
+			    16);
+			continue;
+		}
+		bcopy(p, buf, lp);
+		buf[lp] = '/';
+		bcopy(name, buf + lp + 1, ln);
+		buf[lp + ln + 1] = '\0';
+
+retry:		(void) execve(bp, argv, envp);
+		switch (errno) {
+		case E2BIG:
+			goto done;
+		case ELOOP:
+		case ENAMETOOLONG:
+		case ENOENT:
+			break;
+		case ENOEXEC:
+			for (cnt = 0; argv[cnt]; ++cnt)
+				;
+			memp = alloca((cnt + 2) * sizeof (char *));
+			if (memp == NULL) {
+				/* errno = ENOMEM; XXX override ENOEXEC? */
+				goto done;
+			}
+			memp[0] = "sh";
+			memp[1] = bp;
+			bcopy(argv + 1, memp + 2, cnt * sizeof (char *));
+			execve(_PATH_BSHELL, __DECONST(char **, memp), envp);
+			goto done;
+		case ENOMEM:
+			goto done;
+		case ENOTDIR:
+			break;
+		case ETXTBSY:
+			/*
+			 * We used to retry here, but sh(1) doesn't.
+			 */
+			goto done;
+		default:
+			/*
+			 * EACCES may be for an inaccessible directory or
+			 * a non-executable file.  Call stat() to decide
+			 * which.  This also handles ambiguities for EFAULT
+			 * and EIO, and undocumented errors like ESTALE.
+			 * We hope that the race for a stat() is unimportant.
+			 */
+			save_errno = errno;
+			if (stat(bp, &sb) != 0)
+				break;
+			if (save_errno == EACCES) {
+				eacces = 1;
+				continue;
+			}
+			errno = save_errno;
+			goto done;
+		}
+	}
+	if (eacces)
+		errno = EACCES;
+	else
+		errno = ENOENT;
+done:
+	return (-1);
+}
+
+int
+execvpe(const char *name, char * const argv[], char * const envp[])
+{
+	const char *path;
+
+	/* Get the path we're searching. */
+	if ((path = getenv("PATH")) == NULL)
+		path = _PATH_DEFPATH;
+
+	return (execvPe(name, path, argv, envp));
+}
+
+#if 0
+/*
+ * Get the SPA version
+ */
+static int
+get_zfs_spa_version(void)
+{
+	size_t ver_size;
+	int ver = 0;
+
+	ver_size = sizeof (ver);
+	sysctlbyname("vfs.zfs.version.spa", &ver, &ver_size, NULL, 0);
+
+	return (ver);
+}
+#endif
+
+/*
+ * Get zfs_ioctl_version
+ */
+int
+get_zfs_ioctl_version(void)
+{
+	size_t ver_size;
+	int ver = ZFS_IOCVER_NONE;
+
+	ver_size = sizeof (ver);
+	sysctlbyname("vfs.zfs.version.ioctl", &ver, &ver_size, NULL, 0);
+
+	return (ver);
+}
+
+const char *
+libzfs_error_init(int error)
+{
+
+	return (strerror(error));
+}
+
+int
+zfs_ioctl(libzfs_handle_t *hdl, int request, zfs_cmd_t *zc)
+{
+	return (zfs_ioctl_fd(hdl->libzfs_fd, request, zc));
+}
+
+/*
+ * Verify the required ZFS_DEV device is available and optionally attempt
+ * to load the ZFS modules.  Under normal circumstances the modules
+ * should already have been loaded by some external mechanism.
+ *
+ * Environment variables:
+ * - ZFS_MODULE_LOADING="YES|yes|ON|on" - Attempt to load modules.
+ * - ZFS_MODULE_TIMEOUT="<seconds>"     - Seconds to wait for ZFS_DEV
+ */
+int
+libzfs_load_module(void)
+{
+	/* XXX: modname is "zfs" but file is named "openzfs". */
+	if (modfind("zfs") < 0) {
+		/* Not present in kernel, try loading it. */
+		if (kldload("openzfs") < 0 && errno != EEXIST) {
+			return (errno);
+		}
+	}
+	return (0);
+}
+
+int
+zpool_relabel_disk(libzfs_handle_t *hdl, const char *path, const char *msg)
+{
+	return (0);
+}
+
+int
+zpool_label_disk(libzfs_handle_t *hdl, zpool_handle_t *zhp, char *name)
+{
+	return (0);
+}
+
+int
+find_shares_object(differ_info_t *di)
+{
+	return (0);
+}
+
+/*
+ * Attach/detach the given filesystem to/from the given jail.
+ */
+int
+zfs_jail(zfs_handle_t *zhp, int jailid, int attach)
+{
+	libzfs_handle_t *hdl = zhp->zfs_hdl;
+	zfs_cmd_t zc = { { 0 } };
+	char errbuf[1024];
+	unsigned long cmd;
+	int ret;
+
+	if (attach) {
+		(void) snprintf(errbuf, sizeof (errbuf),
+		    dgettext(TEXT_DOMAIN, "cannot jail '%s'"), zhp->zfs_name);
+	} else {
+		(void) snprintf(errbuf, sizeof (errbuf),
+		    dgettext(TEXT_DOMAIN, "cannot unjail '%s'"), zhp->zfs_name);
+	}
+
+	switch (zhp->zfs_type) {
+	case ZFS_TYPE_VOLUME:
+		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+		    "volumes can not be jailed"));
+		return (zfs_error(hdl, EZFS_BADTYPE, errbuf));
+	case ZFS_TYPE_SNAPSHOT:
+		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+		    "snapshots can not be jailed"));
+		return (zfs_error(hdl, EZFS_BADTYPE, errbuf));
+	case ZFS_TYPE_BOOKMARK:
+		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+		    "bookmarks can not be jailed"));
+		return (zfs_error(hdl, EZFS_BADTYPE, errbuf));
+	case ZFS_TYPE_POOL:
+	case ZFS_TYPE_FILESYSTEM:
+		/* OK */
+		;
+	}
+	assert(zhp->zfs_type == ZFS_TYPE_FILESYSTEM);
+
+	(void) strlcpy(zc.zc_name, zhp->zfs_name, sizeof (zc.zc_name));
+	zc.zc_objset_type = DMU_OST_ZFS;
+	zc.zc_zoneid = jailid;
+
+	cmd = attach ? ZFS_IOC_JAIL : ZFS_IOC_UNJAIL;
+	if ((ret = ioctl(hdl->libzfs_fd, cmd, &zc)) != 0)
+		zfs_standard_error(hdl, errno, errbuf);
+
+	return (ret);
+}
+
+/*
+ * Fill given version buffer with zfs kernel version.
+ * Returns 0 on success, and -1 on error (with errno set)
+ */
+int
+zfs_version_kernel(char *version, int len)
+{
+	size_t l = len;
+
+	return (sysctlbyname("vfs.zfs.version.module",
+	    version, &l, NULL, 0));
+}

lib/libzfs/os/freebsd/libzfs_fsshare.c

@@ -0,0 +1,406 @@
+/*
+ * Copyright (c) 2007 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/vfs.h>
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libutil.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <libintl.h>
+
+#include "libzfs_impl.h"
+
+#define	_PATH_MOUNTDPID	"/var/run/mountd.pid"
+#define	FILE_HEADER	"# !!! DO NOT EDIT THIS FILE MANUALLY !!!\n\n"
+#define	OPTSSIZE	1024
+#define	MAXLINESIZE	(PATH_MAX + OPTSSIZE)
+
+
+void
+sa_fini(sa_handle_t handle)
+{
+}
+
+int
+sa_parse_legacy_options(sa_group_t group, char *options, char *proto)
+{
+	return (SA_OK);
+}
+
+
+int
+zfs_init_libshare(libzfs_handle_t *zhandle, int service)
+{
+	return (SA_OK);
+}
+
+/*
+ * Share the given filesystem according to the options in the specified
+ * protocol specific properties (sharenfs, sharesmb).  We rely
+ * on "libshare" to do the dirty work for us.
+ */
+int
+zfs_share_proto(zfs_handle_t *zhp, zfs_share_proto_t *proto)
+{
+	char mountpoint[ZFS_MAXPROPLEN];
+	char shareopts[ZFS_MAXPROPLEN];
+	char sourcestr[ZFS_MAXPROPLEN];
+	libzfs_handle_t *hdl = zhp->zfs_hdl;
+	zfs_share_proto_t *curr_proto;
+	zprop_source_t sourcetype;
+	int err, ret;
+
+	if (!zfs_is_mountable(zhp, mountpoint, sizeof (mountpoint), NULL, 0))
+		return (0);
+
+	for (curr_proto = proto; *curr_proto != PROTO_END; curr_proto++) {
+		/*
+		 * Return success if there are no share options.
+		 */
+		if (zfs_prop_get(zhp, proto_table[*curr_proto].p_prop,
+		    shareopts, sizeof (shareopts), &sourcetype, sourcestr,
+		    ZFS_MAXPROPLEN, B_FALSE) != 0 ||
+		    strcmp(shareopts, "off") == 0)
+			continue;
+
+		ret = zfs_init_libshare(hdl, SA_INIT_SHARE_API);
+		if (ret != SA_OK) {
+			(void) zfs_error_fmt(hdl, EZFS_SHARENFSFAILED,
+			    dgettext(TEXT_DOMAIN, "cannot share '%s': %s"),
+			    zfs_get_name(zhp), sa_errorstr(ret));
+			return (-1);
+		}
+
+		/*
+		 * If the 'zoned' property is set, then zfs_is_mountable()
+		 * will have already bailed out if we are in the global zone.
+		 * But local zones cannot be NFS servers, so we ignore it for
+		 * local zones as well.
+		 */
+		if (zfs_prop_get_int(zhp, ZFS_PROP_ZONED))
+			continue;
+
+		if (*curr_proto != PROTO_NFS) {
+			fprintf(stderr, "Unsupported share protocol: %d.\n",
+			    *curr_proto);
+			continue;
+		}
+
+		if (strcmp(shareopts, "on") == 0)
+			err = fsshare(ZFS_EXPORTS_PATH, mountpoint, "");
+		else
+			err = fsshare(ZFS_EXPORTS_PATH, mountpoint, shareopts);
+		if (err != 0) {
+			(void) zfs_error_fmt(hdl,
+			    proto_table[*curr_proto].p_share_err,
+			    dgettext(TEXT_DOMAIN, "cannot share '%s'"),
+			    zfs_get_name(zhp));
+			return (-1);
+		}
+
+	}
+	return (0);
+}
+
+/*
+ * Unshare a filesystem by mountpoint.
+ */
+int
+unshare_one(libzfs_handle_t *hdl, const char *name, const char *mountpoint,
+    zfs_share_proto_t proto)
+{
+	int err;
+
+	if (proto != PROTO_NFS) {
+		fprintf(stderr, "No SMB support in FreeBSD yet.\n");
+		return (EOPNOTSUPP);
+	}
+
+	err = fsunshare(ZFS_EXPORTS_PATH, mountpoint);
+	if (err != 0) {
+		zfs_error_aux(hdl, "%s", strerror(err));
+		return (zfs_error_fmt(hdl, EZFS_UNSHARENFSFAILED,
+		    dgettext(TEXT_DOMAIN,
+		    "cannot unshare '%s'"), name));
+	}
+	return (0);
+}
+
+zfs_share_type_t
+is_shared_impl(libzfs_handle_t *hdl, const char *mountpoint,
+    zfs_share_proto_t proto)
+{
+	char buf[MAXPATHLEN], *tab;
+
+	if (hdl->libzfs_sharetab == NULL)
+		return (SHARED_NOT_SHARED);
+
+	(void) fseek(hdl->libzfs_sharetab, 0, SEEK_SET);
+
+	while (fgets(buf, sizeof (buf), hdl->libzfs_sharetab) != NULL) {
+
+		/* the mountpoint is the first entry on each line */
+		if ((tab = strchr(buf, '\t')) == NULL)
+			continue;
+
+		*tab = '\0';
+		if (strcmp(buf, mountpoint) == 0) {
+			if (proto == PROTO_NFS)
+				return (SHARED_NFS);
+		}
+	}
+
+	return (SHARED_NOT_SHARED);
+}
+
+static void
+restart_mountd(void)
+{
+	struct pidfh *pfh;
+	pid_t mountdpid;
+
+	pfh = pidfile_open(_PATH_MOUNTDPID, 0600, &mountdpid);
+	if (pfh != NULL) {
+		/* Mountd is not running. */
+		pidfile_remove(pfh);
+		return;
+	}
+	if (errno != EEXIST) {
+		/* Cannot open pidfile for some reason. */
+		return;
+	}
+	/* We have mountd(8) PID in mountdpid varible. */
+	kill(mountdpid, SIGHUP);
+}
+
+/*
+ * Read one line from a file. Skip comments, empty lines and a line with a
+ * mountpoint specified in the 'skip' argument.
+ */
+static char *
+zgetline(FILE *fd, const char *skip)
+{
+	static char line[MAXLINESIZE];
+	size_t len, skiplen = 0;
+	char *s, last;
+
+	if (skip != NULL)
+		skiplen = strlen(skip);
+	for (;;) {
+		s = fgets(line, sizeof (line), fd);
+		if (s == NULL)
+			return (NULL);
+		/* Skip empty lines and comments. */
+		if (line[0] == '\n' || line[0] == '#')
+			continue;
+		len = strlen(line);
+		if (line[len - 1] == '\n')
+			line[len - 1] = '\0';
+		last = line[skiplen];
+		/* Skip the given mountpoint. */
+		if (skip != NULL && strncmp(skip, line, skiplen) == 0 &&
+		    (last == '\t' || last == ' ' || last == '\0')) {
+			continue;
+		}
+		break;
+	}
+	return (line);
+}
+/* BEGIN CSTYLED */
+/*
+ * Function translate options to a format acceptable by exports(5), eg.
+ *
+ *	-ro -network=192.168.0.0 -mask=255.255.255.0 -maproot=0 freefall.freebsd.org 69.147.83.54
+ *
+ * Accepted input formats:
+ *
+ *	ro,network=192.168.0.0,mask=255.255.255.0,maproot=0,freefall.freebsd.org
+ *	ro network=192.168.0.0 mask=255.255.255.0 maproot=0 freefall.freebsd.org
+ *	-ro,-network=192.168.0.0,-mask=255.255.255.0,-maproot=0,freefall.freebsd.org
+ *	-ro -network=192.168.0.0 -mask=255.255.255.0 -maproot=0 freefall.freebsd.org
+ *
+ * Recognized keywords:
+ *
+ *	ro, maproot, mapall, mask, network, sec, alldirs, public, webnfs, index, quiet
+ *
+ */
+/* END CSTYLED */
+
+static const char *known_opts[] = { "ro", "maproot", "mapall", "mask",
+	"network", "sec", "alldirs", "public", "webnfs", "index", "quiet",
+	NULL };
+static char *
+translate_opts(const char *shareopts)
+{
+	static char newopts[OPTSSIZE];
+	char oldopts[OPTSSIZE];
+	char *o, *s = NULL;
+	unsigned int i;
+	size_t len;
+
+	strlcpy(oldopts, shareopts, sizeof (oldopts));
+	newopts[0] = '\0';
+	s = oldopts;
+	while ((o = strsep(&s, "-, ")) != NULL) {
+		if (o[0] == '\0')
+			continue;
+		for (i = 0; known_opts[i] != NULL; i++) {
+			len = strlen(known_opts[i]);
+			if (strncmp(known_opts[i], o, len) == 0 &&
+			    (o[len] == '\0' || o[len] == '=')) {
+				strlcat(newopts, "-", sizeof (newopts));
+				break;
+			}
+		}
+		strlcat(newopts, o, sizeof (newopts));
+		strlcat(newopts, " ", sizeof (newopts));
+	}
+	return (newopts);
+}
+
+static int
+fsshare_main(const char *file, const char *mountpoint, const char *shareopts,
+    int share)
+{
+	char tmpfile[PATH_MAX];
+	char *line;
+	FILE *newfd, *oldfd;
+	int fd, error;
+
+	newfd = oldfd = NULL;
+	error = 0;
+
+	/*
+	 * Create temporary file in the same directory, so we can atomically
+	 * rename it.
+	 */
+	if (strlcpy(tmpfile, file, sizeof (tmpfile)) >= sizeof (tmpfile))
+		return (ENAMETOOLONG);
+	if (strlcat(tmpfile, ".XXXXXXXX", sizeof (tmpfile)) >= sizeof (tmpfile))
+		return (ENAMETOOLONG);
+	fd = mkstemp(tmpfile);
+	if (fd == -1)
+		return (errno);
+	/*
+	 * File name is random, so we don't really need file lock now, but it
+	 * will be needed after rename(2).
+	 */
+	error = flock(fd, LOCK_EX);
+	assert(error == 0 || (error == -1 && errno == EOPNOTSUPP));
+	newfd = fdopen(fd, "r+");
+	assert(newfd != NULL);
+	/* Open old exports file. */
+	oldfd = fopen(file, "r");
+	if (oldfd == NULL) {
+		if (share) {
+			if (errno != ENOENT) {
+				error = errno;
+				goto out;
+			}
+		} else {
+			/* If there is no exports file, ignore the error. */
+			if (errno == ENOENT)
+				errno = 0;
+			error = errno;
+			goto out;
+		}
+	} else {
+		error = flock(fileno(oldfd), LOCK_EX);
+		assert(error == 0 || (error == -1 && errno == EOPNOTSUPP));
+		error = 0;
+	}
+
+	/* Place big, fat warning at the begining of the file. */
+	fprintf(newfd, "%s", FILE_HEADER);
+	while (oldfd != NULL && (line = zgetline(oldfd, mountpoint)) != NULL)
+		fprintf(newfd, "%s\n", line);
+	if (oldfd != NULL && ferror(oldfd) != 0) {
+		error = ferror(oldfd);
+		goto out;
+	}
+	if (ferror(newfd) != 0) {
+		error = ferror(newfd);
+		goto out;
+	}
+	if (share) {
+		fprintf(newfd, "%s\t%s\n", mountpoint,
+		    translate_opts(shareopts));
+	}
+
+out:
+	if (error != 0)
+		unlink(tmpfile);
+	else {
+		if (rename(tmpfile, file) == -1) {
+			error = errno;
+			unlink(tmpfile);
+		} else {
+			fflush(newfd);
+			/*
+			 * Send SIGHUP to mountd, but unlock exports file later.
+			 */
+			restart_mountd();
+		}
+	}
+	if (oldfd != NULL) {
+		flock(fileno(oldfd), LOCK_UN);
+		fclose(oldfd);
+	}
+	if (newfd != NULL) {
+		flock(fileno(newfd), LOCK_UN);
+		fclose(newfd);
+	}
+	return (error);
+}
+
+/*
+ * Add the given mountpoint to the given exports file.
+ */
+int
+fsshare(const char *file, const char *mountpoint, const char *shareopts)
+{
+
+	return (fsshare_main(file, mountpoint, shareopts, 1));
+}
+
+/*
+ * Remove the given mountpoint from the given exports file.
+ */
+int
+fsunshare(const char *file, const char *mountpoint)
+{
+
+	return (fsshare_main(file, mountpoint, NULL, 0));
+}

lib/libzfs/os/freebsd/libzfs_ioctl_compat.c

@@ -0,0 +1,432 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright 2013 Xin Li <delphij@FreeBSD.org>. All rights reserved.
+ * Copyright 2013 Martin Matuska <mm@FreeBSD.org>. All rights reserved.
+ * Portions Copyright 2005, 2010, Oracle and/or its affiliates.
+ * All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/cred.h>
+#include <sys/dmu.h>
+#include <sys/zio.h>
+#include <sys/nvpair.h>
+#include <sys/dsl_deleg.h>
+#include <sys/zfs_ioctl.h>
+#include "zfs_namecheck.h"
+#include <os/freebsd/zfs/sys/zfs_ioctl_compat.h>
+
+/*
+ * FreeBSD zfs_cmd compatibility with older binaries
+ * appropriately remap/extend the zfs_cmd_t structure
+ */
+void
+zfs_cmd_compat_get(zfs_cmd_t *zc, caddr_t addr, const int cflag)
+{
+
+}
+#if 0
+static int
+zfs_ioctl_compat_get_nvlist(uint64_t nvl, size_t size, int iflag,
+    nvlist_t **nvp)
+{
+	char *packed;
+	int error;
+	nvlist_t *list = NULL;
+
+	/*
+	 * Read in and unpack the user-supplied nvlist.
+	 */
+	if (size == 0)
+		return (EINVAL);
+
+#ifdef _KERNEL
+	packed = kmem_alloc(size, KM_SLEEP);
+	if ((error = ddi_copyin((void *)(uintptr_t)nvl, packed, size,
+	    iflag)) != 0) {
+		kmem_free(packed, size);
+		return (error);
+	}
+#else
+	packed = (void *)(uintptr_t)nvl;
+#endif
+
+	error = nvlist_unpack(packed, size, &list, 0);
+
+#ifdef _KERNEL
+	kmem_free(packed, size);
+#endif
+
+	if (error != 0)
+		return (error);
+
+	*nvp = list;
+	return (0);
+}
+
+static int
+zfs_ioctl_compat_put_nvlist(zfs_cmd_t *zc, nvlist_t *nvl)
+{
+	char *packed = NULL;
+	int error = 0;
+	size_t size;
+
+	VERIFY(nvlist_size(nvl, &size, NV_ENCODE_NATIVE) == 0);
+
+#ifdef _KERNEL
+	packed = kmem_alloc(size, KM_SLEEP);
+	VERIFY(nvlist_pack(nvl, &packed, &size, NV_ENCODE_NATIVE,
+	    KM_SLEEP) == 0);
+
+	if (ddi_copyout(packed,
+	    (void *)(uintptr_t)zc->zc_nvlist_dst, size, zc->zc_iflags) != 0)
+		error = EFAULT;
+	kmem_free(packed, size);
+#else
+	packed = (void *)(uintptr_t)zc->zc_nvlist_dst;
+	VERIFY(nvlist_pack(nvl, &packed, &size, NV_ENCODE_NATIVE,
+	    0) == 0);
+#endif
+
+	zc->zc_nvlist_dst_size = size;
+	return (error);
+}
+
+static void
+zfs_ioctl_compat_fix_stats_nvlist(nvlist_t *nvl)
+{
+	nvlist_t **child;
+	nvlist_t *nvroot = NULL;
+	vdev_stat_t *vs;
+	uint_t c, children, nelem;
+
+	if (nvlist_lookup_nvlist_array(nvl, ZPOOL_CONFIG_CHILDREN,
+	    &child, &children) == 0) {
+		for (c = 0; c < children; c++) {
+			zfs_ioctl_compat_fix_stats_nvlist(child[c]);
+		}
+	}
+
+	if (nvlist_lookup_nvlist(nvl, ZPOOL_CONFIG_VDEV_TREE,
+	    &nvroot) == 0)
+		zfs_ioctl_compat_fix_stats_nvlist(nvroot);
+	if ((nvlist_lookup_uint64_array(nvl, "stats",
+	    (uint64_t **)&vs, &nelem) == 0)) {
+		nvlist_add_uint64_array(nvl,
+		    ZPOOL_CONFIG_VDEV_STATS,
+		    (uint64_t *)vs, nelem);
+		nvlist_remove(nvl, "stats",
+		    DATA_TYPE_UINT64_ARRAY);
+	}
+}
+
+
+static int
+zfs_ioctl_compat_fix_stats(zfs_cmd_t *zc, const int nc)
+{
+	nvlist_t *nv, *nvp = NULL;
+	nvpair_t *elem;
+	int error;
+
+	if ((error = zfs_ioctl_compat_get_nvlist(zc->zc_nvlist_dst,
+	    zc->zc_nvlist_dst_size, zc->zc_iflags, &nv)) != 0)
+		return (error);
+
+	if (nc == 5) { /* ZFS_IOC_POOL_STATS */
+		elem = NULL;
+		while ((elem = nvlist_next_nvpair(nv, elem)) != NULL) {
+			if (nvpair_value_nvlist(elem, &nvp) == 0)
+				zfs_ioctl_compat_fix_stats_nvlist(nvp);
+		}
+		elem = NULL;
+	} else
+		zfs_ioctl_compat_fix_stats_nvlist(nv);
+
+	error = zfs_ioctl_compat_put_nvlist(zc, nv);
+
+	nvlist_free(nv);
+
+	return (error);
+}
+
+static int
+zfs_ioctl_compat_pool_get_props(zfs_cmd_t *zc)
+{
+	nvlist_t *nv, *nva = NULL;
+	int error;
+
+	if ((error = zfs_ioctl_compat_get_nvlist(zc->zc_nvlist_dst,
+	    zc->zc_nvlist_dst_size, zc->zc_iflags, &nv)) != 0)
+		return (error);
+
+	if (nvlist_lookup_nvlist(nv, "used", &nva) == 0) {
+		nvlist_add_nvlist(nv, "allocated", nva);
+		nvlist_remove(nv, "used", DATA_TYPE_NVLIST);
+	}
+
+	if (nvlist_lookup_nvlist(nv, "available", &nva) == 0) {
+		nvlist_add_nvlist(nv, "free", nva);
+		nvlist_remove(nv, "available", DATA_TYPE_NVLIST);
+	}
+
+	error = zfs_ioctl_compat_put_nvlist(zc, nv);
+
+	nvlist_free(nv);
+
+	return (error);
+}
+#endif
+
+#ifdef _KERNEL
+int
+zfs_ioctl_compat_pre(zfs_cmd_t *zc, int *vec, const int cflag)
+{
+	int error = 0;
+
+	/* are we creating a clone? */
+	if (*vec == ZFS_IOC_CREATE && zc->zc_value[0] != '\0')
+		*vec = ZFS_IOC_CLONE;
+
+	if (cflag == ZFS_CMD_COMPAT_V15) {
+		switch (*vec) {
+
+		case 7: /* ZFS_IOC_POOL_SCRUB (v15) */
+			zc->zc_cookie = POOL_SCAN_SCRUB;
+			break;
+		}
+	}
+
+	return (error);
+}
+
+void
+zfs_ioctl_compat_post(zfs_cmd_t *zc, int vec, const int cflag)
+{
+	if (cflag == ZFS_CMD_COMPAT_V15) {
+		switch (vec) {
+		case ZFS_IOC_POOL_CONFIGS:
+		case ZFS_IOC_POOL_STATS:
+		case ZFS_IOC_POOL_TRYIMPORT:
+			zfs_ioctl_compat_fix_stats(zc, vec);
+			break;
+		case 41: /* ZFS_IOC_POOL_GET_PROPS (v15) */
+			zfs_ioctl_compat_pool_get_props(zc);
+			break;
+		}
+	}
+}
+
+nvlist_t *
+zfs_ioctl_compat_innvl(zfs_cmd_t *zc, nvlist_t *innvl, const int vec,
+    const int cflag)
+{
+	nvlist_t *nvl, *tmpnvl, *hnvl;
+	nvpair_t *elem;
+	char *poolname, *snapname;
+	int err;
+
+	if (cflag == ZFS_CMD_COMPAT_NONE || cflag == ZFS_CMD_COMPAT_LZC ||
+	    cflag == ZFS_CMD_COMPAT_ZCMD || cflag == ZFS_CMD_COMPAT_EDBP ||
+	    cflag == ZFS_CMD_COMPAT_RESUME || cflag == ZFS_CMD_COMPAT_INLANES)
+		goto out;
+
+	switch (vec) {
+	case ZFS_IOC_CREATE:
+		nvl = fnvlist_alloc();
+		fnvlist_add_int32(nvl, "type", zc->zc_objset_type);
+		if (innvl != NULL) {
+			fnvlist_add_nvlist(nvl, "props", innvl);
+			nvlist_free(innvl);
+		}
+		return (nvl);
+	break;
+	case ZFS_IOC_CLONE:
+		nvl = fnvlist_alloc();
+		fnvlist_add_string(nvl, "origin", zc->zc_value);
+		if (innvl != NULL) {
+			fnvlist_add_nvlist(nvl, "props", innvl);
+			nvlist_free(innvl);
+		}
+		return (nvl);
+	break;
+	case ZFS_IOC_SNAPSHOT:
+		if (innvl == NULL)
+			goto out;
+		nvl = fnvlist_alloc();
+		fnvlist_add_nvlist(nvl, "props", innvl);
+		tmpnvl = fnvlist_alloc();
+		snapname = kmem_asprintf("%s@%s", zc->zc_name, zc->zc_value);
+		fnvlist_add_boolean(tmpnvl, snapname);
+		kmem_free(snapname, strlen(snapname + 1));
+		/* check if we are doing a recursive snapshot */
+		if (zc->zc_cookie)
+			dmu_get_recursive_snaps_nvl(zc->zc_name, zc->zc_value,
+			    tmpnvl);
+		fnvlist_add_nvlist(nvl, "snaps", tmpnvl);
+		fnvlist_free(tmpnvl);
+		nvlist_free(innvl);
+		/* strip dataset part from zc->zc_name */
+		zc->zc_name[strcspn(zc->zc_name, "/@")] = '\0';
+		return (nvl);
+	break;
+	case ZFS_IOC_SPACE_SNAPS:
+		nvl = fnvlist_alloc();
+		fnvlist_add_string(nvl, "firstsnap", zc->zc_value);
+		if (innvl != NULL)
+			nvlist_free(innvl);
+		return (nvl);
+	break;
+	case ZFS_IOC_DESTROY_SNAPS:
+		if (innvl == NULL && cflag == ZFS_CMD_COMPAT_DEADMAN)
+			goto out;
+		nvl = fnvlist_alloc();
+		if (innvl != NULL) {
+			fnvlist_add_nvlist(nvl, "snaps", innvl);
+		} else {
+			/*
+			 * We are probably called by even older binaries,
+			 * allocate and populate nvlist with recursive
+			 * snapshots
+			 */
+			if (zfs_component_namecheck(zc->zc_value, NULL,
+			    NULL) == 0) {
+				tmpnvl = fnvlist_alloc();
+				if (dmu_get_recursive_snaps_nvl(zc->zc_name,
+				    zc->zc_value, tmpnvl) == 0)
+					fnvlist_add_nvlist(nvl, "snaps",
+					    tmpnvl);
+				nvlist_free(tmpnvl);
+			}
+		}
+		if (innvl != NULL)
+			nvlist_free(innvl);
+		/* strip dataset part from zc->zc_name */
+		zc->zc_name[strcspn(zc->zc_name, "/@")] = '\0';
+		return (nvl);
+	break;
+	case ZFS_IOC_HOLD:
+		nvl = fnvlist_alloc();
+		tmpnvl = fnvlist_alloc();
+		if (zc->zc_cleanup_fd != -1)
+			fnvlist_add_int32(nvl, "cleanup_fd",
+			    (int32_t)zc->zc_cleanup_fd);
+		if (zc->zc_cookie) {
+			hnvl = fnvlist_alloc();
+			if (dmu_get_recursive_snaps_nvl(zc->zc_name,
+			    zc->zc_value, hnvl) == 0) {
+				elem = NULL;
+				while ((elem = nvlist_next_nvpair(hnvl,
+				    elem)) != NULL) {
+					nvlist_add_string(tmpnvl,
+					    nvpair_name(elem), zc->zc_string);
+				}
+			}
+			nvlist_free(hnvl);
+		} else {
+			snapname = kmem_asprintf("%s@%s", zc->zc_name,
+			    zc->zc_value);
+			nvlist_add_string(tmpnvl, snapname, zc->zc_string);
+			kmem_free(snapname, strlen(snapname + 1));
+		}
+		fnvlist_add_nvlist(nvl, "holds", tmpnvl);
+		nvlist_free(tmpnvl);
+		if (innvl != NULL)
+			nvlist_free(innvl);
+		/* strip dataset part from zc->zc_name */
+		zc->zc_name[strcspn(zc->zc_name, "/@")] = '\0';
+		return (nvl);
+	break;
+	case ZFS_IOC_RELEASE:
+		nvl = fnvlist_alloc();
+		tmpnvl = fnvlist_alloc();
+		if (zc->zc_cookie) {
+			hnvl = fnvlist_alloc();
+			if (dmu_get_recursive_snaps_nvl(zc->zc_name,
+			    zc->zc_value, hnvl) == 0) {
+				elem = NULL;
+				while ((elem = nvlist_next_nvpair(hnvl,
+				    elem)) != NULL) {
+					fnvlist_add_boolean(tmpnvl,
+					    zc->zc_string);
+					fnvlist_add_nvlist(nvl,
+					    nvpair_name(elem), tmpnvl);
+				}
+			}
+			nvlist_free(hnvl);
+		} else {
+			snapname = kmem_asprintf("%s@%s", zc->zc_name,
+			    zc->zc_value);
+			fnvlist_add_boolean(tmpnvl, zc->zc_string);
+			fnvlist_add_nvlist(nvl, snapname, tmpnvl);
+			kmem_free(snapname, strlen(snapname + 1));
+		}
+		nvlist_free(tmpnvl);
+		if (innvl != NULL)
+			nvlist_free(innvl);
+		/* strip dataset part from zc->zc_name */
+		zc->zc_name[strcspn(zc->zc_name, "/@")] = '\0';
+		return (nvl);
+	break;
+	}
+out:
+	return (innvl);
+}
+
+nvlist_t *
+zfs_ioctl_compat_outnvl(zfs_cmd_t *zc, nvlist_t *outnvl, const int vec,
+    const int cflag)
+{
+	nvlist_t *tmpnvl;
+
+	if (cflag == ZFS_CMD_COMPAT_NONE || cflag == ZFS_CMD_COMPAT_LZC ||
+	    cflag == ZFS_CMD_COMPAT_ZCMD || cflag == ZFS_CMD_COMPAT_EDBP ||
+	    cflag == ZFS_CMD_COMPAT_RESUME || cflag == ZFS_CMD_COMPAT_INLANES)
+		return (outnvl);
+
+	switch (vec) {
+	case ZFS_IOC_SPACE_SNAPS:
+		(void) nvlist_lookup_uint64(outnvl, "used", &zc->zc_cookie);
+		(void) nvlist_lookup_uint64(outnvl, "compressed",
+		    &zc->zc_objset_type);
+		(void) nvlist_lookup_uint64(outnvl, "uncompressed",
+		    &zc->zc_perm_action);
+		nvlist_free(outnvl);
+		/* return empty outnvl */
+		tmpnvl = fnvlist_alloc();
+		return (tmpnvl);
+	break;
+	case ZFS_IOC_CREATE:
+	case ZFS_IOC_CLONE:
+	case ZFS_IOC_HOLD:
+	case ZFS_IOC_RELEASE:
+		nvlist_free(outnvl);
+		/* return empty outnvl */
+		tmpnvl = fnvlist_alloc();
+		return (tmpnvl);
+	break;
+	}
+
+	return (outnvl);
+}
+#endif /* KERNEL */

lib/libzfs/os/freebsd/libzfs_zmount.c

@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2006 Pawel Jakub Dawidek <pjd@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * This file implements Solaris compatible zmount() function.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/mount.h>
+#include <sys/uio.h>
+#include <sys/mntent.h>
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mnttab.h>
+#include <sys/errno.h>
+
+static void
+build_iovec(struct iovec **iov, int *iovlen, const char *name, void *val,
+    size_t len)
+{
+	int i;
+
+	if (*iovlen < 0)
+		return;
+	i = *iovlen;
+	*iov = realloc(*iov, sizeof (**iov) * (i + 2));
+	if (*iov == NULL) {
+		*iovlen = -1;
+		return;
+	}
+	(*iov)[i].iov_base = strdup(name);
+	(*iov)[i].iov_len = strlen(name) + 1;
+	i++;
+	(*iov)[i].iov_base = val;
+	if (len == (size_t)-1) {
+		if (val != NULL)
+			len = strlen(val) + 1;
+		else
+			len = 0;
+	}
+	(*iov)[i].iov_len = (int)len;
+	*iovlen = ++i;
+}
+
+static int
+do_mount_(const char *spec, const char *dir, int mflag, char *fstype,
+    char *dataptr, int datalen, char *optptr, int optlen)
+{
+	struct iovec *iov;
+	char *optstr, *p, *tofree;
+	int iovlen, rv;
+
+	assert(spec != NULL);
+	assert(dir != NULL);
+	assert(fstype != NULL);
+	assert(strcmp(fstype, MNTTYPE_ZFS) == 0);
+	assert(dataptr == NULL);
+	assert(datalen == 0);
+	assert(optptr != NULL);
+	assert(optlen > 0);
+
+	tofree = optstr = strdup(optptr);
+	assert(optstr != NULL);
+
+	iov = NULL;
+	iovlen = 0;
+	if (strstr(optstr, MNTOPT_REMOUNT) != NULL)
+		build_iovec(&iov, &iovlen, "update", NULL, 0);
+	if (strstr(optstr, MNTOPT_NOXATTR) == NULL &&
+	    strstr(optstr, MNTOPT_XATTR) == NULL &&
+	    strstr(optstr, MNTOPT_SAXATTR) == NULL &&
+	    strstr(optstr, MNTOPT_DIRXATTR) == NULL)
+		build_iovec(&iov, &iovlen, "xattr", NULL, 0);
+	if (mflag & MS_RDONLY)
+		build_iovec(&iov, &iovlen, "ro", NULL, 0);
+	build_iovec(&iov, &iovlen, "fstype", fstype, (size_t)-1);
+	build_iovec(&iov, &iovlen, "fspath", __DECONST(char *, dir),
+	    (size_t)-1);
+	build_iovec(&iov, &iovlen, "from", __DECONST(char *, spec), (size_t)-1);
+	while ((p = strsep(&optstr, ",/")) != NULL)
+		build_iovec(&iov, &iovlen, p, NULL, (size_t)-1);
+	rv = nmount(iov, iovlen, 0);
+	free(tofree);
+	if (rv < 0)
+		return (errno);
+	return (rv);
+}
+
+int
+do_mount(const char *src, const char *mntpt, char *opts, int flags)
+{
+
+	return (do_mount_(src, mntpt, flags, MNTTYPE_ZFS, NULL, 0, opts,
+	    sizeof (mntpt)));
+}
+
+int
+do_unmount(const char *mntpt, int flags)
+{
+
+	return (unmount(mntpt, flags));
+}
+
+int
+zfs_mount_delegation_check(void)
+{
+	return (0);
+}
+
+/*
+ * Check if we are doing an overlay mount.
+ * Returns B_TRUE if the mount would overlay, otherwise B_FALSE.
+ */
+boolean_t
+zfs_mount_overlay_check(const char *mountpoint)
+{
+	/* FreeBSD always allows overlay mounts. */
+	return (B_FALSE);
+}