Index: sys/nfsclient/nfs_vfsops.c
===================================================================
--- sys/nfsclient/nfs_vfsops.c	(revision 242773)
+++ sys/nfsclient/nfs_vfsops.c	(working copy)
@@ -1193,7 +1193,7 @@ nfs_mount(struct mount *mp)
 out:
 	if (!error) {
 		MNT_ILOCK(mp);
-		mp->mnt_kern_flag |= (MNTK_MPSAFE|MNTK_LOOKUP_SHARED);
+		mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED;
 		MNT_IUNLOCK(mp);
 	}
 	return (error);
Index: sys/fs/nfsclient/nfs_clvfsops.c
===================================================================
--- sys/fs/nfsclient/nfs_clvfsops.c	(revision 242773)
+++ sys/fs/nfsclient/nfs_clvfsops.c	(working copy)
@@ -1136,8 +1136,7 @@ nfs_mount(struct mount *mp)
 out:
 	if (!error) {
 		MNT_ILOCK(mp);
-		mp->mnt_kern_flag |= MNTK_MPSAFE | MNTK_LOOKUP_SHARED |
-		    MNTK_NO_IOPF;
+		mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_NO_IOPF;
 		MNT_IUNLOCK(mp);
 	}
 	return (error);
Index: sys/fs/pseudofs/pseudofs.c
===================================================================
--- sys/fs/pseudofs/pseudofs.c	(revision 242773)
+++ sys/fs/pseudofs/pseudofs.c	(working copy)
@@ -308,7 +308,6 @@ pfs_mount(struct pfs_info *pi, struct mount *mp)
 
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE;
 	MNT_IUNLOCK(mp);
 	mp->mnt_data = pi;
 	vfs_getnewfsid(mp);
Index: sys/fs/tmpfs/tmpfs_vfsops.c
===================================================================
--- sys/fs/tmpfs/tmpfs_vfsops.c	(revision 242773)
+++ sys/fs/tmpfs/tmpfs_vfsops.c	(working copy)
@@ -253,7 +253,6 @@ tmpfs_mount(struct mount *mp)
 
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE;
 	MNT_IUNLOCK(mp);
 
 	mp->mnt_data = tmp;
Index: sys/fs/fuse/fuse_vfsops.c
===================================================================
--- sys/fs/fuse/fuse_vfsops.c	(revision 242773)
+++ sys/fs/fuse/fuse_vfsops.c	(working copy)
@@ -339,7 +339,6 @@ fuse_vfsop_mount(struct mount *mp)
 
 	vfs_getnewfsid(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE;
 	if (subtype) {
 		strlcat(mp->mnt_stat.f_fstypename, ".", MFSNAMELEN);
 		strlcat(mp->mnt_stat.f_fstypename, subtype, MFSNAMELEN);
Index: sys/fs/nullfs/null_vfsops.c
===================================================================
--- sys/fs/nullfs/null_vfsops.c	(revision 242773)
+++ sys/fs/nullfs/null_vfsops.c	(working copy)
@@ -189,8 +189,7 @@ nullfs_mount(struct mount *mp)
 	}
 	MNT_ILOCK(mp);
 	mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag &
-	    (MNTK_MPSAFE | MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED |
-	    MNTK_EXTENDED_SHARED);
+	    (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED);
 	mp->mnt_kern_flag |= MNTK_LOOKUP_EXCL_DOTDOT;
 	MNT_IUNLOCK(mp);
 	mp->mnt_data = xmp;
Index: sys/fs/cd9660/cd9660_vfsops.c
===================================================================
--- sys/fs/cd9660/cd9660_vfsops.c	(revision 242773)
+++ sys/fs/cd9660/cd9660_vfsops.c	(working copy)
@@ -376,8 +376,7 @@ iso_mountfs(devvp, mp)
 	mp->mnt_maxsymlinklen = 0;
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE | MNTK_LOOKUP_SHARED |
-	    MNTK_EXTENDED_SHARED;
+	mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED;
 	MNT_IUNLOCK(mp);
 	isomp->im_mountp = mp;
 	isomp->im_dev = dev;
Index: sys/fs/unionfs/union_vfsops.c
===================================================================
--- sys/fs/unionfs/union_vfsops.c	(revision 242773)
+++ sys/fs/unionfs/union_vfsops.c	(working copy)
@@ -266,11 +266,6 @@ unionfs_domount(struct mount *mp)
 	ump->um_copymode = copymode;
 	ump->um_whitemode = whitemode;
 
-	MNT_ILOCK(mp);
-	if ((lowerrootvp->v_mount->mnt_kern_flag & MNTK_MPSAFE) &&
-	    (upperrootvp->v_mount->mnt_kern_flag & MNTK_MPSAFE))
-		mp->mnt_kern_flag |= MNTK_MPSAFE;
-	MNT_IUNLOCK(mp);
 	mp->mnt_data = ump;
 
 	/*
Index: sys/fs/unionfs/union_vnops.c
===================================================================
--- sys/fs/unionfs/union_vnops.c	(revision 242773)
+++ sys/fs/unionfs/union_vnops.c	(working copy)
@@ -1867,8 +1867,7 @@ unionfs_lock(struct vop_lock1_args *ap)
 	if ((revlock = unionfs_get_llt_revlock(vp, flags)) == 0)
 		panic("unknown lock type: 0x%x", flags & LK_TYPE_MASK);
 
-	if ((mp->mnt_kern_flag & MNTK_MPSAFE) != 0 &&
-	    (vp->v_iflag & VI_OWEINACT) != 0)
+	if ((vp->v_iflag & VI_OWEINACT) != 0)
 		flags |= LK_NOWAIT;
 
 	/*
Index: sys/fs/devfs/devfs_vfsops.c
===================================================================
--- sys/fs/devfs/devfs_vfsops.c	(revision 242773)
+++ sys/fs/devfs/devfs_vfsops.c	(working copy)
@@ -131,8 +131,7 @@ devfs_mount(struct mount *mp)
 
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE | MNTK_LOOKUP_SHARED |
-	    MNTK_EXTENDED_SHARED;
+	mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED;
 #ifdef MAC
 	mp->mnt_flag |= MNT_MULTILABEL;
 #endif
Index: sys/fs/nandfs/nandfs_vfsops.c
===================================================================
--- sys/fs/nandfs/nandfs_vfsops.c	(revision 242773)
+++ sys/fs/nandfs/nandfs_vfsops.c	(working copy)
@@ -1383,7 +1383,6 @@ nandfs_mountfs(struct vnode *devvp, struct mount *
 	nmp->nm_ronly = ronly;
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE;
 	MNT_IUNLOCK(mp);
 	nmp->nm_nandfsdev = nandfsdev;
 	/* Add our mountpoint */
Index: sys/fs/ext2fs/ext2_vfsops.c
===================================================================
--- sys/fs/ext2fs/ext2_vfsops.c	(revision 242773)
+++ sys/fs/ext2fs/ext2_vfsops.c	(working copy)
@@ -665,8 +665,7 @@ ext2_mountfs(struct vnode *devvp, struct mount *mp
 	 * Initialize filesystem stat information in mount struct.
 	 */
 	MNT_ILOCK(mp);
- 	mp->mnt_kern_flag |= MNTK_MPSAFE | MNTK_LOOKUP_SHARED |
-            MNTK_EXTENDED_SHARED;
+ 	mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED;
 	MNT_IUNLOCK(mp);
 	return (0);
 out:
Index: sys/fs/fdescfs/fdesc_vfsops.c
===================================================================
--- sys/fs/fdescfs/fdesc_vfsops.c	(revision 242773)
+++ sys/fs/fdescfs/fdesc_vfsops.c	(working copy)
@@ -107,9 +107,6 @@ fdesc_mount(struct mount *mp)
 	VOP_UNLOCK(rvp, 0);
 	/* XXX -- don't mark as local to work around fts() problems */
 	/*mp->mnt_flag |= MNT_LOCAL;*/
-	MNT_ILOCK(mp);
-	mp->mnt_kern_flag |= MNTK_MPSAFE;
-	MNT_IUNLOCK(mp);
 	vfs_getnewfsid(mp);
 
 	vfs_mountedfrom(mp, "fdescfs");
Index: sys/fs/udf/udf_vfsops.c
===================================================================
--- sys/fs/udf/udf_vfsops.c	(revision 242773)
+++ sys/fs/udf/udf_vfsops.c	(working copy)
@@ -355,8 +355,7 @@ udf_mountfs(struct vnode *devvp, struct mount *mp)
 	mp->mnt_stat.f_fsid.val[1] = mp->mnt_vfc->vfc_typenum;
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE | MNTK_LOOKUP_SHARED |
-	    MNTK_EXTENDED_SHARED;
+	mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED;
 	MNT_IUNLOCK(mp);
 	udfmp->im_mountp = mp;
 	udfmp->im_dev = dev;
Index: sys/fs/msdosfs/msdosfs_vfsops.c
===================================================================
--- sys/fs/msdosfs/msdosfs_vfsops.c	(revision 242773)
+++ sys/fs/msdosfs/msdosfs_vfsops.c	(working copy)
@@ -760,7 +760,6 @@ mountmsdosfs(struct vnode *devvp, struct mount *mp
 	mp->mnt_stat.f_fsid.val[1] = mp->mnt_vfc->vfc_typenum;
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE;
 	MNT_IUNLOCK(mp);
 
 	if (pmp->pm_flags & MSDOSFS_LARGEFS)
Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c	(revision 242773)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c	(working copy)
@@ -1132,7 +1132,6 @@ zfs_domount(vfs_t *vfsp, char *osname)
 
 	vfsp->vfs_data = zfsvfs;
 	vfsp->mnt_flag |= MNT_LOCAL;
-	vfsp->mnt_kern_flag |= MNTK_MPSAFE;
 	vfsp->mnt_kern_flag |= MNTK_LOOKUP_SHARED;
 	vfsp->mnt_kern_flag |= MNTK_SHARED_WRITES;
 	vfsp->mnt_kern_flag |= MNTK_EXTENDED_SHARED;
Index: sys/sys/mount.h
===================================================================
--- sys/sys/mount.h	(revision 242773)
+++ sys/sys/mount.h	(working copy)
@@ -385,7 +385,7 @@ void          __mnt_vnode_markerfree(struct vnode
 #define	MNTK_SUSPEND	0x08000000	/* request write suspension */
 #define	MNTK_SUSPEND2	0x04000000	/* block secondary writes */
 #define	MNTK_SUSPENDED	0x10000000	/* write operations are suspended */
-#define	MNTK_MPSAFE	0x20000000	/* Filesystem is MPSAFE. */
+#define	MNTK_UNUSED25	0x20000000	/*  --available-- */
 #define MNTK_LOOKUP_SHARED	0x40000000 /* FS supports shared lock lookups */
 #define	MNTK_NOKNOTE	0x80000000	/* Don't send KNOTEs from VOP hooks */
 
Index: sys/gnu/fs/reiserfs/reiserfs_vfsops.c
===================================================================
--- sys/gnu/fs/reiserfs/reiserfs_vfsops.c	(revision 242773)
+++ sys/gnu/fs/reiserfs/reiserfs_vfsops.c	(working copy)
@@ -580,7 +580,6 @@ reiserfs_mountfs(struct vnode *devvp, struct mount
 	mp->mnt_stat.f_fsid.val[1] = mp->mnt_vfc->vfc_typenum;
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE;
 	MNT_IUNLOCK(mp);
 #if defined(si_mountpoint)
 	devvp->v_rdev->si_mountpoint = mp;
Index: sys/ufs/ffs/ffs_vfsops.c
===================================================================
--- sys/ufs/ffs/ffs_vfsops.c	(revision 242773)
+++ sys/ufs/ffs/ffs_vfsops.c	(working copy)
@@ -1063,8 +1063,8 @@ ffs_mountfs(devvp, mp, td)
 	 * Initialize filesystem stat information in mount struct.
 	 */
 	MNT_ILOCK(mp);
-	mp->mnt_kern_flag |= MNTK_MPSAFE | MNTK_LOOKUP_SHARED |
-	    MNTK_EXTENDED_SHARED | MNTK_NO_IOPF;
+	mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED |
+	    MNTK_NO_IOPF;
 	MNT_IUNLOCK(mp);
 #ifdef UFS_EXTATTR
 #ifdef UFS_EXTATTR_AUTOSTART
Index: sys/kern/uipc_mqueue.c
===================================================================
--- sys/kern/uipc_mqueue.c	(revision 242773)
+++ sys/kern/uipc_mqueue.c	(working copy)
@@ -582,7 +582,6 @@ mqfs_mount(struct mount *mp)
 	mp->mnt_data = &mqfs_data;
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_MPSAFE;
 	MNT_IUNLOCK(mp);
 	vfs_getnewfsid(mp);
 
Index: sys/kern/vfs_subr.c
===================================================================
--- sys/kern/vfs_subr.c	(revision 242773)
+++ sys/kern/vfs_subr.c	(working copy)
@@ -3110,7 +3110,6 @@ DB_SHOW_COMMAND(mount, db_show_mount)
 	MNT_KERN_FLAG(MNTK_SUSPEND);
 	MNT_KERN_FLAG(MNTK_SUSPEND2);
 	MNT_KERN_FLAG(MNTK_SUSPENDED);
-	MNT_KERN_FLAG(MNTK_MPSAFE);
 	MNT_KERN_FLAG(MNTK_LOOKUP_SHARED);
 	MNT_KERN_FLAG(MNTK_NOKNOTE);
 #undef MNT_KERN_FLAG