Index: sys/sys/mount.h
===================================================================
--- sys/sys/mount.h	(revision 220936)
+++ sys/sys/mount.h	(working copy)
@@ -138,8 +138,12 @@ struct vfsopt {
 	int	len;
 	int	pos;
 	int	seen;
+	int	flags;
 };
 
+/* vfsopt flags */
+#define	VFSOPT_CANCELONLY	0x01
+
 /*
  * Structure per mounted filesystem.  Each mounted filesystem has an
  * array of operations and an instance record.  The filesystems are
Index: sys/kern/vfs_mount.c
===================================================================
--- sys/kern/vfs_mount.c	(revision 220937)
+++ sys/kern/vfs_mount.c	(working copy)
@@ -284,12 +284,9 @@ vfs_buildopts(struct uio *auio, struct v
 			goto bad;
 		}
 
-		opt = malloc(sizeof(struct vfsopt), M_MOUNT, M_WAITOK);
+		opt = malloc(sizeof(struct vfsopt), M_MOUNT, M_WAITOK | M_ZERO);
 		opt->name = malloc(namelen, M_MOUNT, M_WAITOK);
-		opt->value = NULL;
-		opt->len = 0;
 		opt->pos = i / 2;
-		opt->seen = 0;
 
 		/*
 		 * Do this early, so jumps to "bad" will free the current
@@ -335,15 +332,11 @@ bad:
 /*
  * Merge the old mount options with the new ones passed
  * in the MNT_UPDATE case.
- *
- * XXX: This function will keep a "nofoo" option in the new
- * options.  E.g, if the option's canonical name is "foo",
- * "nofoo" ends up in the mount point's active options.
  */
 static void
 vfs_mergeopts(struct vfsoptlist *toopts, struct vfsoptlist *oldopts)
 {
-	struct vfsopt *opt, *new;
+	struct vfsopt *new, *opt, *opt_tmp;
 
 	TAILQ_FOREACH(opt, oldopts, link) {
 		new = malloc(sizeof(struct vfsopt), M_MOUNT, M_WAITOK);
@@ -355,9 +348,18 @@ vfs_mergeopts(struct vfsoptlist *toopts,
 			new->value = NULL;
 		new->len = opt->len;
 		new->seen = opt->seen;
+		new->flags = opt->flags;
 		TAILQ_INSERT_HEAD(toopts, new, link);
 	}
 	vfs_sanitizeopts(toopts);
+	/*
+	 * Remove options which shouldn't end up in the mount point's
+	 * active options.
+	 */
+	TAILQ_FOREACH_SAFE(opt, toopts, link, opt_tmp) {
+		if ((opt->flags & VFSOPT_CANCELONLY) != 0)
+			vfs_freeopt(toopts, opt);
+	}
 }
 
 /*
@@ -584,40 +586,16 @@ vfs_donmount(struct thread *td, int fsfl
 			fsflags &= ~MNT_ASYNC;
 		else if (strcmp(opt->name, "noatime") == 0)
 			fsflags |= MNT_NOATIME;
-		else if (strcmp(opt->name, "atime") == 0) {
-			free(opt->name, M_MOUNT);
-			opt->name = strdup("nonoatime", M_MOUNT);
-		}
 		else if (strcmp(opt->name, "noclusterr") == 0)
 			fsflags |= MNT_NOCLUSTERR;
-		else if (strcmp(opt->name, "clusterr") == 0) {
-			free(opt->name, M_MOUNT);
-			opt->name = strdup("nonoclusterr", M_MOUNT);
-		}
 		else if (strcmp(opt->name, "noclusterw") == 0)
 			fsflags |= MNT_NOCLUSTERW;
-		else if (strcmp(opt->name, "clusterw") == 0) {
-			free(opt->name, M_MOUNT);
-			opt->name = strdup("nonoclusterw", M_MOUNT);
-		}
 		else if (strcmp(opt->name, "noexec") == 0)
 			fsflags |= MNT_NOEXEC;
-		else if (strcmp(opt->name, "exec") == 0) {
-			free(opt->name, M_MOUNT);
-			opt->name = strdup("nonoexec", M_MOUNT);
-		}
 		else if (strcmp(opt->name, "nosuid") == 0)
 			fsflags |= MNT_NOSUID;
-		else if (strcmp(opt->name, "suid") == 0) {
-			free(opt->name, M_MOUNT);
-			opt->name = strdup("nonosuid", M_MOUNT);
-		}
 		else if (strcmp(opt->name, "nosymfollow") == 0)
 			fsflags |= MNT_NOSYMFOLLOW;
-		else if (strcmp(opt->name, "symfollow") == 0) {
-			free(opt->name, M_MOUNT);
-			opt->name = strdup("nonosymfollow", M_MOUNT);
-		}
 		else if (strcmp(opt->name, "noro") == 0)
 			fsflags &= ~MNT_RDONLY;
 		else if (strcmp(opt->name, "rw") == 0)
@@ -1372,27 +1350,27 @@ vfs_opterror(struct vfsoptlist *opts, co
  */
 
 /*
- * Check that no unknown options are given
+ * Check that no unknown options are given and mark options which
+ * should not become active with the VFSOPT_CANCELONLY flag.
  */
 int
 vfs_filteropt(struct vfsoptlist *opts, const char **legal)
 {
 	struct vfsopt *opt;
 	char errmsg[255];
-	const char **t, *p, *q;
-	int ret = 0;
+	const char **t, *p;
+	int ret;
+
+	ret = 0;
 
 	TAILQ_FOREACH(opt, opts, link) {
 		p = opt->name;
-		q = NULL;
-		if (p[0] == 'n' && p[1] == 'o')
-			q = p + 2;
 		for(t = global_opts; *t != NULL; t++) {
 			if (strcmp(*t, p) == 0)
 				break;
-			if (q != NULL) {
-				if (strcmp(*t, q) == 0)
-					break;
+			if (vfs_equalopts(*t, p)) {
+				opt->flags |= VFSOPT_CANCELONLY;
+				break;
 			}
 		}
 		if (*t != NULL)
@@ -1400,9 +1378,9 @@ vfs_filteropt(struct vfsoptlist *opts, c
 		for(t = legal; *t != NULL; t++) {
 			if (strcmp(*t, p) == 0)
 				break;
-			if (q != NULL) {
-				if (strcmp(*t, q) == 0)
-					break;
+			if (vfs_equalopts(*t, p)) {
+				opt->flags |= VFSOPT_CANCELONLY;
+				break;
 			}
 		}
 		if (*t != NULL)