Index: UPDATING
===================================================================
--- UPDATING	(revision 227308)
+++ UPDATING	(working copy)
@@ -22,6 +22,12 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 10.x IS SLOW
 	machines to maximize performance.  (To disable malloc debugging, run
 	ln -s aj /etc/malloc.conf.)
 
+20111105:
+	The option VFS_ALLOW_NONMPSAFE option has been added in order to
+	explicitely support non-MPSAFE filesystems.
+	It is on by default for all supported platform at this present
+	time.
+
 20111101:
 	The broken amd(4) driver has been replaced with esp(4) in the amd64,
 	i386 and pc98 GENERIC kernel configuration files.
Index: sys/arm/conf/DEFAULTS
===================================================================
--- sys/arm/conf/DEFAULTS	(revision 227308)
+++ sys/arm/conf/DEFAULTS	(working copy)
@@ -9,3 +9,5 @@ device		mem
 
 options 	GEOM_PART_BSD
 options 	GEOM_PART_MBR
+
+options		VFS_ALLOW_NONMPSAFE
Index: sys/powerpc/conf/DEFAULTS
===================================================================
--- sys/powerpc/conf/DEFAULTS	(revision 227308)
+++ sys/powerpc/conf/DEFAULTS	(working copy)
@@ -12,3 +12,6 @@ device		uart_z8530
 
 options 	GEOM_PART_APM
 options 	GEOM_PART_MBR
+
+# Allow mounting non-MPSAFE filesystems
+options		VFS_ALLOW_NONMPSAFE
Index: sys/sparc64/conf/DEFAULTS
===================================================================
--- sys/sparc64/conf/DEFAULTS	(revision 227308)
+++ sys/sparc64/conf/DEFAULTS	(working copy)
@@ -21,3 +21,6 @@ options 	GEOM_PART_VTOC8
 options 	SUNKBD_EMULATE_ATKBD
 
 options 	NEW_PCIB
+
+# Allow mounting non-MPSAFE filesystems
+options		VFS_ALLOW_NONMPSAFE
Index: sys/conf/NOTES
===================================================================
--- sys/conf/NOTES	(revision 227308)
+++ sys/conf/NOTES	(working copy)
@@ -1104,6 +1104,9 @@ options 	XFS
 # unsuitable for inclusion on machines with untrusted local users.
 options 	VFS_AIO
 
+# Enable mounting of non-MPSAFE filesystems.
+options 	VFS_ALLOW_NONMPSAFE
+
 # Cryptographically secure random number generator; /dev/random
 device		random
 
Index: sys/conf/options
===================================================================
--- sys/conf/options	(revision 227308)
+++ sys/conf/options	(working copy)
@@ -185,6 +185,7 @@ SYSVSHM		opt_sysvipc.h
 SW_WATCHDOG	opt_watchdog.h
 TURNSTILE_PROFILING
 VFS_AIO
+VFS_ALLOW_NONMPSAFE
 VERBOSE_SYSINIT	opt_global.h
 WLCACHE		opt_wavelan.h
 WLDEBUG		opt_wavelan.h
Index: sys/kern/vfs_mount.c
===================================================================
--- sys/kern/vfs_mount.c	(revision 227308)
+++ sys/kern/vfs_mount.c	(working copy)
@@ -37,6 +37,8 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_vfs_allow_nonmpsafe.h"
+
 #include <sys/param.h>
 #include <sys/conf.h>
 #include <sys/fcntl.h>
@@ -798,6 +800,14 @@ vfs_domount_first(
 	 * get.  No freeing of cn_pnbuf.
 	 */
 	error = VFS_MOUNT(mp);
+#ifndef VFS_ALLOW_NONMPSAFE
+	if (error == 0 && VFS_NEEDSGIANT(mp)) {
+		(void)VFS_UNMOUNT(mp, fsflags);
+		error = ENXIO;
+		printf("%s: Mounting non-MPSAFE fs (%s) is disabled\n",
+		    __func__, mp->mnt_vfc->vfc_name);
+	}
+#endif
 	if (error != 0) {
 		vfs_unbusy(mp);
 		vfs_mount_destroy(mp);
@@ -807,6 +817,11 @@ vfs_domount_first(
 		vrele(vp);
 		return (error);
 	}
+#ifdef VFS_ALLOW_NONMPSAFE
+	if (VFS_NEEDSGIANT(mp))
+		printf("%s: Mounting non-MPSAFE fs (%s) is deprecated\n",
+		    __func__, mp->mnt_vfc->vfc_name);
+#endif
 
 	if (mp->mnt_opt != NULL)
 		vfs_freeopts(mp->mnt_opt);
Index: sys/ia64/conf/DEFAULTS
===================================================================
--- sys/ia64/conf/DEFAULTS	(revision 227308)
+++ sys/ia64/conf/DEFAULTS	(working copy)
@@ -20,3 +20,6 @@ options 	GEOM_PART_GPT
 options 	GEOM_PART_MBR
 
 options 	NEW_PCIB
+
+# Allow mounting non-MPSAFE filesystems
+options		VFS_ALLOW_NONMPSAFE
Index: sys/mips/conf/DEFAULTS
===================================================================
--- sys/mips/conf/DEFAULTS	(revision 227308)
+++ sys/mips/conf/DEFAULTS	(working copy)
@@ -9,3 +9,5 @@ device		uart_ns8250
 
 options 	GEOM_PART_BSD
 options 	GEOM_PART_MBR
+
+options		VFS_ALLOW_NONMPSAFE
Index: sys/pc98/conf/DEFAULTS
===================================================================
--- sys/pc98/conf/DEFAULTS	(revision 227308)
+++ sys/pc98/conf/DEFAULTS	(working copy)
@@ -29,3 +29,6 @@ options 	GEOM_PART_PC98
 device		atpic
 
 options 	NEW_PCIB
+
+# Allow mounting non-MPSAFE filesystems
+options		VFS_ALLOW_NONMPSAFE
Index: sys/i386/conf/DEFAULTS
===================================================================
--- sys/i386/conf/DEFAULTS	(revision 227308)
+++ sys/i386/conf/DEFAULTS	(working copy)
@@ -30,3 +30,6 @@ options 	NATIVE
 device		atpic
 
 options 	NEW_PCIB
+
+# Allow mounting non-MPSAFE filesystems
+options		VFS_ALLOW_NONMPSAFE
Index: sys/amd64/conf/DEFAULTS
===================================================================
--- sys/amd64/conf/DEFAULTS	(revision 227308)
+++ sys/amd64/conf/DEFAULTS	(working copy)
@@ -22,3 +22,6 @@ options 	GEOM_PART_EBR_COMPAT
 options 	GEOM_PART_MBR
 
 options 	NEW_PCIB
+
+# Allow mounting non-MPSAFE filesystems
+options		VFS_ALLOW_NONMPSAFE