diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 18ad471..c8b4d97 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -368,7 +368,7 @@ vfs_busy(struct mount *mp, int flags, struct mtx *interlkp)
 	}
 	if (interlkp)
 		mtx_unlock(interlkp);
-	lkflags = LK_SHARED | LK_INTERLOCK;
+	lkflags = LK_SHARED | LK_INTERLOCK | LK_NOWAIT;
 	if (lockmgr(&mp->mnt_lock, lkflags, MNT_MTX(mp)))
 		panic("vfs_busy: unexpected lock failure");
 	return (0);
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 2301a34..c730781 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -873,6 +873,10 @@ _vn_lock(struct vnode *vp, int flags, char *file, int line)
 	VNASSERT((flags & LK_TYPE_MASK) != 0, vp,
 	    ("vn_lock called with no locktype."));
 	do {
+#ifdef DEBUG_VFS_LOCKS
+		KASSERT(vp->v_holdcnt != 0,
+		    ("vn_lock %p: zero hold count", vp));
+#endif
 		error = VOP_LOCK1(vp, flags, file, line);
 		flags &= ~LK_INTERLOCK;	/* Interlock is always dropped. */
 		KASSERT((flags & LK_RETRY) == 0 || error == 0,
diff --git a/sys/ufs/ffs/ffs_vnops.c b/sys/ufs/ffs/ffs_vnops.c
index 7b1af28..38dc2b6 100644
--- a/sys/ufs/ffs/ffs_vnops.c
+++ b/sys/ufs/ffs/ffs_vnops.c
@@ -361,6 +361,10 @@ ffs_lock(ap)
 		vp = ap->a_vp;
 		flags = ap->a_flags;
 		for (;;) {
+#ifdef DEBUG_VFS_LOCKS
+			KASSERT(vp->v_holdcnt != 0,
+			    ("ffs_lock %p: zero hold count", vp));
+#endif
 			lkp = vp->v_vnlock;
 			result = _lockmgr_args(lkp, flags, VI_MTX(vp),
 			    LK_WMESG_DEFAULT, LK_PRIO_DEFAULT, LK_TIMO_DEFAULT,
diff --git a/sys/ufs/ufs/ufs_lookup.c b/sys/ufs/ufs/ufs_lookup.c
index 042ecd0..e345048 100644
--- a/sys/ufs/ufs/ufs_lookup.c
+++ b/sys/ufs/ufs/ufs_lookup.c
@@ -157,6 +157,7 @@ ufs_lookup(ap)
 	int nameiop = cnp->cn_nameiop;
 	ino_t ino;
 	int ltype;
+	struct mount *mp;
 
 	bp = NULL;
 	slotoffset = -1;
@@ -578,9 +579,27 @@ found:
 	pdp = vdp;
 	if (flags & ISDOTDOT) {
 		ltype = VOP_ISLOCKED(pdp);
+		mp = pdp->v_mount;
+		vhold(pdp);
+		for (;;) {
+			error = vfs_busy(mp, LK_NOWAIT, NULL);
+			if (error == 0)
+				break;
+			VOP_UNLOCK(pdp, 0);
+			pause("ufs_dd", 1);
+			vn_lock(pdp, ltype | LK_RETRY);
+			VI_LOCK(pdp);
+			if (pdp->v_iflag & VI_DOOMED) {
+				vdropl(pdp);
+				return (ENOENT);
+			}
+			VI_UNLOCK(pdp);
+		}
 		VOP_UNLOCK(pdp, 0);	/* race to get the inode */
-		error = VFS_VGET(pdp->v_mount, ino, cnp->cn_lkflags, &tdp);
+		error = VFS_VGET(mp, ino, cnp->cn_lkflags, &tdp);
+		vfs_unbusy(mp);
 		vn_lock(pdp, ltype | LK_RETRY);
+		vdrop(pdp);
 		if (error)
 			return (error);
 		*vpp = tdp;