8 files changed, 2516 insertions, 1718 deletions

diff --git a/sys/fs/unionfs/union.h b/sys/fs/unionfs/union.h
index 1fc5f996cab0..02a897101472 100644
--- a/sys/fs/unionfs/union.h
+++ b/sys/fs/unionfs/union.h
@@ -49,8 +49,8 @@ struct union_args {
 #define UNMNT_OPMASK	0x0003
 
 struct union_mount {
-	struct vnode	*um_uppervp;
-	struct vnode	*um_lowervp;
+	struct vnode	*um_uppervp;	/* UN_ULOCK holds locking state */
+	struct vnode	*um_lowervp;	/* Left unlocked */
 	struct ucred	*um_cred;	/* Credentials of user calling mount */
 	int		um_cmode;	/* cmask from mount process */
 	int		um_op;		/* Operation mode */
@@ -58,6 +58,10 @@ struct union_mount {
 
 #ifdef KERNEL
 
+#ifndef DIAGNOSTIC
+#define DIAGNOSTIC
+#endif
+
 /*
  * DEFDIRMODE is the mode bits used to create a shadow directory.
  */
@@ -67,9 +71,14 @@ struct union_mount {
 #define UN_FILEMODE ((VRWMODE)|(VRWMODE>>3)|(VRWMODE>>6))
 
 /*
- * A cache of vnode references
+ * A cache of vnode references	(hangs off v_data)
+ *
+ * Placing un_lock as the first elements theoretically allows us to
+ * use the vop_stdlock functions.  However, we need to make sure of
+ * certain side effects so we will still punch in our own code.
  */
 struct union_node {
+	struct lock		un_lock;
 	LIST_ENTRY(union_node)	un_cache;	/* Hash chain */
 	struct vnode		*un_vnode;	/* Back pointer */
 	struct vnode	        *un_uppervp;	/* overlaying object */
@@ -79,6 +88,7 @@ struct union_node {
 	char			*un_path;	/* saved component name */
 	int			un_hash;	/* saved un_path hash value */
 	int			un_openl;	/* # of opens on lowervp */
+	int			un_exclcnt;	/* exclusive count */
 	unsigned int		un_flags;
 	struct vnode		**un_dircache;	/* cached union stack */
 	off_t			un_uppersz;	/* size of upper object */
@@ -88,14 +98,25 @@ struct union_node {
 #endif
 };
 
-#define UN_WANT		0x01
-#define UN_LOCKED	0x02
-#define UN_ULOCK	0x04		/* Upper node is locked */
-#define UN_KLOCK	0x08		/* Keep upper node locked on vput */
-#define UN_CACHED	0x10		/* In union cache */
+/*
+ * XXX UN_ULOCK -	indicates that the uppervp is locked
+ *
+ * UN_CACHED -	node is in the union cache
+ */
+
+/*#define UN_ULOCK	0x04*/	/* Upper node is locked */
+#define UN_CACHED	0x10	/* In union cache */
+
+/*
+ * Hash table locking flags
+ */
+
+#define UNVP_WANT	0x01
+#define UNVP_LOCKED	0x02
 
 extern int union_allocvp __P((struct vnode **, struct mount *,
-				struct vnode *, struct vnode *,
+				struct vnode *, 
+				struct vnode *, 
 				struct componentname *, struct vnode *,
 				struct vnode *, int));
 extern int union_freevp __P((struct vnode *));
@@ -113,6 +134,7 @@ extern int union_cn_close __P((struct vnode *, int, struct ucred *,
 extern void union_removed_upper __P((struct union_node *un));
 extern struct vnode *union_lowervp __P((struct vnode *));
 extern void union_newsize __P((struct vnode *, off_t, off_t));
+extern void union_vm_coherency __P((struct vnode *, struct uio *, int));
 
 extern int (*union_dircheckp) __P((struct proc *, struct vnode **,
 				 struct file *));
@@ -124,6 +146,11 @@ extern int (*union_dircheckp) __P((struct proc *, struct vnode **,
 #define	UPPERVP(vp) (VTOUNION(vp)->un_uppervp)
 #define OTHERVP(vp) (UPPERVP(vp) ? UPPERVP(vp) : LOWERVP(vp))
 
+#define UDEBUG(x)	if (uniondebug) printf x
+#define UDEBUG_ENABLED	1
+
 extern vop_t **union_vnodeop_p;
 extern struct vfsops union_vfsops;
+extern int uniondebug;
+
 #endif /* KERNEL */
diff --git a/sys/fs/unionfs/union_subr.c b/sys/fs/unionfs/union_subr.c
index ed09a65fbb4a..c03153c4894b 100644
--- a/sys/fs/unionfs/union_subr.c
+++ b/sys/fs/unionfs/union_subr.c
@@ -53,6 +53,7 @@
 #include <vm/vm.h>
 #include <vm/vm_extern.h>	/* for vnode_pager_setsize */
 #include <vm/vm_zone.h>
+#include <vm/vm_object.h>	/* for vm cache coherency */
 #include <miscfs/union/union.h>
 
 #include <sys/proc.h>
@@ -97,7 +98,7 @@ union_init()
 
 	for (i = 0; i < NHASH; i++)
 		LIST_INIT(&unhead[i]);
-	bzero((caddr_t) unvplock, sizeof(unvplock));
+	bzero((caddr_t)unvplock, sizeof(unvplock));
 	return (0);
 }
 
@@ -105,15 +106,12 @@ static int
 union_list_lock(ix)
 	int ix;
 {
-
-	if (unvplock[ix] & UN_LOCKED) {
-		unvplock[ix] |= UN_WANT;
+	if (unvplock[ix] & UNVP_LOCKED) {
+		unvplock[ix] |= UNVP_WANT;
 		(void) tsleep((caddr_t) &unvplock[ix], PINOD, "unllck", 0);
 		return (1);
 	}
-
-	unvplock[ix] |= UN_LOCKED;
-
+	unvplock[ix] |= UNVP_LOCKED;
 	return (0);
 }
 
@@ -121,15 +119,25 @@ static void
 union_list_unlock(ix)
 	int ix;
 {
+	unvplock[ix] &= ~UNVP_LOCKED;
 
-	unvplock[ix] &= ~UN_LOCKED;
-
-	if (unvplock[ix] & UN_WANT) {
-		unvplock[ix] &= ~UN_WANT;
+	if (unvplock[ix] & UNVP_WANT) {
+		unvplock[ix] &= ~UNVP_WANT;
 		wakeup((caddr_t) &unvplock[ix]);
 	}
 }
 
+/*
+ *	union_updatevp:
+ *
+ *	The uppervp, if not NULL, must be referenced and not locked by us
+ *	The lowervp, if not NULL, must be referenced.
+ *
+ *	if uppervp and lowervp match pointers already installed, nothing
+ *	happens. The passed vp's (when matching) are not adjusted.  This
+ *	routine may only be called by union_newupper() and union_newlower().
+ */
+
 static void
 union_updatevp(un, uppervp, lowervp)
 	struct union_node *un;
@@ -153,9 +161,10 @@ union_updatevp(un, uppervp, lowervp)
 		uhash = nhash;
 	}
 
-	if (lhash != uhash)
+	if (lhash != uhash) {
 		while (union_list_lock(lhash))
 			continue;
+	}
 
 	while (union_list_lock(uhash))
 		continue;
@@ -177,10 +186,6 @@ union_updatevp(un, uppervp, lowervp)
 				free(un->un_path, M_TEMP);
 				un->un_path = 0;
 			}
-			if (un->un_dirvp) {
-				vrele(un->un_dirvp);
-				un->un_dirvp = NULLVP;
-			}
 		}
 		un->un_lowervp = lowervp;
 		un->un_lowersz = VNOVAL;
@@ -189,7 +194,6 @@ union_updatevp(un, uppervp, lowervp)
 	if (un->un_uppervp != uppervp) {
 		if (un->un_uppervp)
 			vrele(un->un_uppervp);
-
 		un->un_uppervp = uppervp;
 		un->un_uppersz = VNOVAL;
 	}
@@ -202,21 +206,30 @@ union_updatevp(un, uppervp, lowervp)
 	union_list_unlock(nhash);
 }
 
+/*
+ * Set a new lowervp.  The passed lowervp must be referenced and will be
+ * stored in the vp in a referenced state. 
+ */
+
 static void
 union_newlower(un, lowervp)
 	struct union_node *un;
 	struct vnode *lowervp;
 {
-
 	union_updatevp(un, un->un_uppervp, lowervp);
 }
 
+/*
+ * Set a new uppervp.  The passed uppervp must be locked and will be 
+ * stored in the vp in a locked state.  The caller should not unlock
+ * uppervp.
+ */
+
 static void
 union_newupper(un, uppervp)
 	struct union_node *un;
 	struct vnode *uppervp;
 {
-
 	union_updatevp(un, uppervp, un->un_lowervp);
 }
 
@@ -253,27 +266,51 @@ union_newsize(vp, uppersz, lowersz)
 	}
 
 	if (sz != VNOVAL) {
-#ifdef DEBUG
-		printf("union: %s size now %ld\n",
-			uppersz != VNOVAL ? "upper" : "lower", (long) sz);
-#endif
+		UDEBUG(("union: %s size now %ld\n",
+			(uppersz != VNOVAL ? "upper" : "lower"), (long)sz));
 		vnode_pager_setsize(vp, sz);
 	}
 }
 
 /*
- * allocate a union_node/vnode pair.  the vnode is
- * referenced and locked.  the new vnode is returned
- * via (vpp).  (mp) is the mountpoint of the union filesystem,
- * (dvp) is the parent directory where the upper layer object
- * should exist (but doesn't) and (cnp) is the componentname
- * information which is partially copied to allow the upper
- * layer object to be created at a later time.  (uppervp)
- * and (lowervp) reference the upper and lower layer objects
- * being mapped.  either, but not both, can be nil.
- * if supplied, (uppervp) is locked.
- * the reference is either maintained in the new union_node
- * object which is allocated, or they are vrele'd.
+ *	union_allocvp:	allocate a union_node and associate it with a
+ *			parent union_node and one or two vnodes.
+ *
+ *	vpp	Holds the returned vnode locked and referenced if no 
+ *		error occurs.
+ *
+ *	mp	Holds the mount point.  mp may or may not be busied. 
+ *		allocvp makes no changes to mp.
+ *
+ *	dvp	Holds the parent union_node to the one we wish to create.
+ *		XXX may only be used to traverse an uncopied lowervp-based
+ *		tree?  XXX
+ *
+ *		dvp may or may not be locked.  allocvp makes no changes
+ *		to dvp.
+ *
+ *	upperdvp Holds the parent vnode to uppervp, generally used along
+ *		with path component information to create a shadow of
+ *		lowervp when uppervp does not exist.
+ *
+ *		upperdvp is referenced but unlocked on entry, and will be
+ *		dereferenced on return.
+ *
+ *	uppervp	Holds the new uppervp vnode to be stored in the 
+ *		union_node we are allocating.  uppervp is referenced but
+ *		not locked, and will be dereferenced on return.
+ *
+ *	lowervp	Holds the new lowervp vnode to be stored in the
+ *		union_node we are allocating.  uppervp is referenced but
+ *		not locked, and will be dereferenced on return.
+ * 
+ *	cnp	Holds path component information to be coupled with
+ *		lowervp and upperdvp to allow unionfs to create an uppervp
+ *		later on.  Only used if lowervp is valid.  The conents
+ *		of cnp is only valid for the duration of the call.
+ *
+ *	docache	Determine whether this node should be entered in the
+ *		cache or whether it should be destroyed as soon as possible.
  *
  * all union_nodes are maintained on a singly-linked
  * list.  new nodes are only allocated when they cannot
@@ -292,12 +329,13 @@ union_newsize(vp, uppersz, lowersz)
  * zero references to it and so it needs to removed from
  * the vnode free list.
  */
+
 int
-union_allocvp(vpp, mp, undvp, dvp, cnp, uppervp, lowervp, docache)
+union_allocvp(vpp, mp, dvp, upperdvp, cnp, uppervp, lowervp, docache)
 	struct vnode **vpp;
 	struct mount *mp;
-	struct vnode *undvp;		/* parent union vnode */
-	struct vnode *dvp;		/* may be null */
+	struct vnode *dvp;		/* parent union vnode */
+	struct vnode *upperdvp;		/* parent vnode of uppervp */
 	struct componentname *cnp;	/* may be null */
 	struct vnode *uppervp;		/* may be null */
 	struct vnode *lowervp;		/* may be null */
@@ -307,6 +345,7 @@ union_allocvp(vpp, mp, undvp, dvp, cnp, uppervp, lowervp, docache)
 	struct union_node *un = 0;
 	struct vnode *xlowervp = NULLVP;
 	struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
+	struct proc *p = (cnp) ? cnp->cn_proc : curproc;
 	int hash = 0;
 	int vflag;
 	int try;
@@ -382,65 +421,76 @@ loop:
 
 	if (un) {
 		/*
-		 * Obtain a lock on the union_node.
-		 * uppervp is locked, though un->un_uppervp
-		 * may not be.  this doesn't break the locking
-		 * hierarchy since in the case that un->un_uppervp
-		 * is not yet locked it will be vrele'd and replaced
-		 * with uppervp.
+		 * Obtain a lock on the union_node.  Everything is unlocked
+		 * except for dvp, so check that case.  If they match, our
+		 * new un is already locked.  Otherwise we have to lock our
+		 * new un.
+		 *
+		 * A potential deadlock situation occurs when we are holding
+		 * one lock while trying to get another.  We must follow 
+		 * strict ordering rules to avoid it.  We try to locate dvp
+		 * by scanning up from un_vnode, since the most likely 
+		 * scenario is un being under dvp.
 		 */
 
-		if ((dvp != NULLVP) && (uppervp == dvp)) {
+		if (dvp && un->un_vnode != dvp) {
+			struct vnode *scan = un->un_vnode;
+
+			do {
+				scan = VTOUNION(scan)->un_pvp;
+			} while (scan && scan->v_tag == VT_UNION && scan != dvp);
+			if (scan != dvp) {
+				/*
+				 * our new un is above dvp (we never saw dvp
+				 * while moving up the tree).
+				 */
+				VREF(dvp);
+				VOP_UNLOCK(dvp, 0, p);
+				error = vn_lock(un->un_vnode, LK_EXCLUSIVE, p);
+				vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
+				vrele(dvp);
+			} else {
+				/*
+				 * our new un is under dvp
+				 */
+				error = vn_lock(un->un_vnode, LK_EXCLUSIVE, p);
+			}
+		} else if (dvp == NULLVP) {
 			/*
-			 * Access ``.'', so (un) will already
-			 * be locked.  Since this process has
-			 * the lock on (uppervp) no other
-			 * process can hold the lock on (un).
+			 * dvp is NULL, we need to lock un.
 			 */
-#ifdef DIAGNOSTIC
-			if ((un->un_flags & UN_LOCKED) == 0)
-				panic("union: . not locked");
-			else if (curproc && un->un_pid != curproc->p_pid &&
-				    un->un_pid > -1 && curproc->p_pid > -1)
-				panic("union: allocvp not lock owner");
-#endif
+			error = vn_lock(un->un_vnode, LK_EXCLUSIVE, p);
 		} else {
-			if (un->un_flags & UN_LOCKED) {
-				vrele(UNIONTOV(un));
-				un->un_flags |= UN_WANT;
-				(void) tsleep((caddr_t) &un->un_flags, PINOD, "unalvp", 0);
-				goto loop;
-			}
-			un->un_flags |= UN_LOCKED;
-
-#ifdef DIAGNOSTIC
-			if (curproc)
-				un->un_pid = curproc->p_pid;
-			else
-				un->un_pid = -1;
-#endif
+			/*
+			 * dvp == un->un_vnode, we are already locked.
+			 */
+			error = 0;
 		}
 
-		/*
-		 * At this point, the union_node is locked,
-		 * un->un_uppervp may not be locked, and uppervp
-		 * is locked or nil.
-		 */
+		if (error)
+			goto loop;
 
 		/*
-		 * Save information about the upper layer.
+		 * At this point, the union_node is locked and referenced.
+		 *
+		 * uppervp is locked and referenced or NULL, lowervp is
+		 * referenced or NULL.
 		 */
+		UDEBUG(("Modify existing un %p vn %p upper %p(refs %d) -> %p(refs %d)\n",
+			un, un->un_vnode, un->un_uppervp, 
+			(un->un_uppervp ? un->un_uppervp->v_usecount : -99),
+			uppervp,
+			(uppervp ? uppervp->v_usecount : -99)
+		));
+
 		if (uppervp != un->un_uppervp) {
+			KASSERT(uppervp == NULL || uppervp->v_usecount > 0, ("union_allocvp: too few refs %d (at least 1 required) on uppervp", uppervp->v_usecount));
 			union_newupper(un, uppervp);
 		} else if (uppervp) {
+			KASSERT(uppervp->v_usecount > 1, ("union_allocvp: too few refs %d (at least 2 required) on uppervp", uppervp->v_usecount));
 			vrele(uppervp);
 		}
 
-		if (un->un_uppervp) {
-			un->un_flags |= UN_ULOCK;
-			un->un_flags &= ~UN_KLOCK;
-		}
-
 		/*
 		 * Save information about the lower layer.
 		 * This needs to keep track of pathname
@@ -456,12 +506,22 @@ loop:
 				bcopy(cnp->cn_nameptr, un->un_path,
 						cnp->cn_namelen);
 				un->un_path[cnp->cn_namelen] = '\0';
-				VREF(dvp);
-				un->un_dirvp = dvp;
 			}
 		} else if (lowervp) {
 			vrele(lowervp);
 		}
+
+		/*
+		 * and upperdvp
+		 */
+		if (upperdvp != un->un_dirvp) {
+			if (un->un_dirvp)
+				vrele(un->un_dirvp);
+			un->un_dirvp = upperdvp;
+		} else if (upperdvp) {
+			vrele(upperdvp);
+		}
+
 		*vpp = UNIONTOV(un);
 		return (0);
 	}
@@ -477,17 +537,22 @@ loop:
 			goto loop;
 	}
 
+	/*
+	 * Create new node rather then replace old node
+	 */
+
 	error = getnewvnode(VT_UNION, mp, union_vnodeop_p, vpp);
 	if (error) {
-		if (uppervp) {
-			if (dvp == uppervp)
-				vrele(uppervp);
-			else
-				vput(uppervp);
-		}
+		/*
+		 * If an error occurs clear out vnodes.
+		 */
 		if (lowervp)
 			vrele(lowervp);
-
+		if (uppervp) 
+			vrele(uppervp);
+		if (upperdvp)
+			vrele(upperdvp);
+		*vpp = NULL;
 		goto out;
 	}
 
@@ -499,37 +564,34 @@ loop:
 		(*vpp)->v_type = uppervp->v_type;
 	else
 		(*vpp)->v_type = lowervp->v_type;
+
 	un = VTOUNION(*vpp);
+	bzero(un, sizeof(*un));
+
+	lockinit(&un->un_lock, PVFS, "unlock", 0, 0);
+	vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY, p);
+
 	un->un_vnode = *vpp;
 	un->un_uppervp = uppervp;
 	un->un_uppersz = VNOVAL;
 	un->un_lowervp = lowervp;
 	un->un_lowersz = VNOVAL;
-	un->un_pvp = undvp;
-	if (undvp != NULLVP)
-		VREF(undvp);
+	un->un_dirvp = upperdvp;
+	un->un_pvp = dvp;		/* only parent dir in new allocation */
+	if (dvp != NULLVP)
+		VREF(dvp);
 	un->un_dircache = 0;
 	un->un_openl = 0;
-	un->un_flags = UN_LOCKED;
-	if (un->un_uppervp)
-		un->un_flags |= UN_ULOCK;
-#ifdef DIAGNOSTIC
-	if (curproc)
-		un->un_pid = curproc->p_pid;
-	else
-		un->un_pid = -1;
-#endif
+
 	if (cnp && (lowervp != NULLVP)) {
 		un->un_hash = cnp->cn_hash;
 		un->un_path = malloc(cnp->cn_namelen+1, M_TEMP, M_WAITOK);
 		bcopy(cnp->cn_nameptr, un->un_path, cnp->cn_namelen);
 		un->un_path[cnp->cn_namelen] = '\0';
-		VREF(dvp);
-		un->un_dirvp = dvp;
 	} else {
 		un->un_hash = 0;
 		un->un_path = 0;
-		un->un_dirvp = 0;
+		un->un_dirvp = NULL;
 	}
 
 	if (docache) {
@@ -537,10 +599,10 @@ loop:
 		un->un_flags |= UN_CACHED;
 	}
 
+out:
 	if (xlowervp)
 		vrele(xlowervp);
 
-out:
 	if (docache)
 		union_list_unlock(hash);
 
@@ -558,16 +620,26 @@ union_freevp(vp)
 		LIST_REMOVE(un, un_cache);
 	}
 
-	if (un->un_pvp != NULLVP)
+	if (un->un_pvp != NULLVP) {
 		vrele(un->un_pvp);
-	if (un->un_uppervp != NULLVP)
+		un->un_pvp = NULL;
+	}
+	if (un->un_uppervp != NULLVP) {
 		vrele(un->un_uppervp);
-	if (un->un_lowervp != NULLVP)
+		un->un_uppervp = NULL;
+	}
+	if (un->un_lowervp != NULLVP) {
 		vrele(un->un_lowervp);
-	if (un->un_dirvp != NULLVP)
+		un->un_lowervp = NULL;
+	}
+	if (un->un_dirvp != NULLVP) {
 		vrele(un->un_dirvp);
-	if (un->un_path)
+		un->un_dirvp = NULL;
+	}
+	if (un->un_path) {
 		free(un->un_path, M_TEMP);
+		un->un_path = NULL;
+	}
 
 	FREE(vp->v_data, M_TEMP);
 	vp->v_data = 0;
@@ -579,6 +651,9 @@ union_freevp(vp)
  * copyfile.  copy the vnode (fvp) to the vnode (tvp)
  * using a sequence of reads and writes.  both (fvp)
  * and (tvp) are locked on entry and exit.
+ *
+ * fvp and tvp are both exclusive locked on call, but their refcount's
+ * haven't been bumped at all.
  */
 static int
 union_copyfile(fvp, tvp, cred, p)
@@ -600,48 +675,62 @@ union_copyfile(fvp, tvp, cred, p)
 	 * give up at the first sign of trouble.
 	 */
 
+	bzero(&uio, sizeof(uio));
+
 	uio.uio_procp = p;
 	uio.uio_segflg = UIO_SYSSPACE;
 	uio.uio_offset = 0;
 
-	VOP_UNLOCK(fvp, 0, p);				/* XXX */
 	VOP_LEASE(fvp, p, cred, LEASE_READ);
-	vn_lock(fvp, LK_EXCLUSIVE | LK_RETRY, p);	/* XXX */
-	VOP_UNLOCK(tvp, 0, p);				/* XXX */
 	VOP_LEASE(tvp, p, cred, LEASE_WRITE);
-	vn_lock(tvp, LK_EXCLUSIVE | LK_RETRY, p);	/* XXX */
 
 	buf = malloc(MAXBSIZE, M_TEMP, M_WAITOK);
 
 	/* ugly loop follows... */
 	do {
 		off_t offset = uio.uio_offset;
+		int count;
+		int bufoffset;
 
+		/*
+		 * Setup for big read
+		 */
 		uio.uio_iov = &iov;
 		uio.uio_iovcnt = 1;
 		iov.iov_base = buf;
 		iov.iov_len = MAXBSIZE;
 		uio.uio_resid = iov.iov_len;
 		uio.uio_rw = UIO_READ;
-		error = VOP_READ(fvp, &uio, 0, cred);
 
-		if (error == 0) {
+		if ((error = VOP_READ(fvp, &uio, 0, cred)) != 0)
+			break;
+
+		/*
+		 * Get bytes read, handle read eof case and setup for
+		 * write loop
+		 */
+		if ((count = MAXBSIZE - uio.uio_resid) == 0)
+			break;
+		bufoffset = 0;
+
+		/*
+		 * Write until an error occurs or our buffer has been
+		 * exhausted, then update the offset for the next read.
+		 */
+		while (bufoffset < count) {
 			uio.uio_iov = &iov;
 			uio.uio_iovcnt = 1;
-			iov.iov_base = buf;
-			iov.iov_len = MAXBSIZE - uio.uio_resid;
-			uio.uio_offset = offset;
+			iov.iov_base = buf + bufoffset;
+			iov.iov_len = count - bufoffset;
+			uio.uio_offset = offset + bufoffset;
 			uio.uio_rw = UIO_WRITE;
 			uio.uio_resid = iov.iov_len;
 
-			if (uio.uio_resid == 0)
+			if ((error = VOP_WRITE(tvp, &uio, 0, cred)) != 0)
 				break;
-
-			do {
-				error = VOP_WRITE(tvp, &uio, 0, cred);
-			} while ((uio.uio_resid > 0) && (error == 0));
+			bufoffset += (count - bufoffset) - uio.uio_resid;
 		}
-
+		uio.uio_offset = offset + bufoffset;
 	} while (error == 0);
 
 	free(buf, M_TEMP);
@@ -649,9 +738,10 @@ union_copyfile(fvp, tvp, cred, p)
 }
 
 /*
- * (un) is assumed to be locked on entry and remains
- * locked on exit.
+ *
+ * un's vnode is assumed to be locked on entry and remains locked on exit.
  */
+
 int
 union_copyup(un, docopy, cred, p)
 	struct union_node *un;
@@ -676,12 +766,9 @@ union_copyup(un, docopy, cred, p)
 	if (error)
 		return (error);
 
-	/* at this point, uppervp is locked */
-	union_newupper(un, uvp);
-	un->un_flags |= UN_ULOCK;
-
 	lvp = un->un_lowervp;
 
+	KASSERT(uvp->v_usecount > 0, ("copy: uvp refcount 0: %d", uvp->v_usecount));
 	if (docopy) {
 		/*
 		 * XX - should not ignore errors
@@ -689,23 +776,22 @@ union_copyup(un, docopy, cred, p)
 		 */
 		vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, p);
 		error = VOP_OPEN(lvp, FREAD, cred, p);
+		if (error == 0 && vn_canvmio(lvp) == TRUE)
+			error = vfs_object_create(lvp, p, cred);
 		if (error == 0) {
 			error = union_copyfile(lvp, uvp, cred, p);
 			VOP_UNLOCK(lvp, 0, p);
 			(void) VOP_CLOSE(lvp, FREAD, cred, p);
 		}
-#ifdef DEBUG
 		if (error == 0)
-			uprintf("union: copied up %s\n", un->un_path);
-#endif
+			UDEBUG(("union: copied up %s\n", un->un_path));
 
 	}
-	un->un_flags &= ~UN_ULOCK;
 	VOP_UNLOCK(uvp, 0, p);
+	union_newupper(un, uvp);
+	KASSERT(uvp->v_usecount > 0, ("copy: uvp refcount 0: %d", uvp->v_usecount));
 	union_vn_close(uvp, FWRITE, cred, p);
-	vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY, p);
-	un->un_flags |= UN_ULOCK;
-
+	KASSERT(uvp->v_usecount > 0, ("copy: uvp refcount 0: %d", uvp->v_usecount));
 	/*
 	 * Subsequent IOs will go to the top layer, so
 	 * call close on the lower vnode and open on the
@@ -721,6 +807,8 @@ union_copyup(un, docopy, cred, p)
 			(void) VOP_CLOSE(lvp, FREAD, cred, p);
 			(void) VOP_OPEN(uvp, FREAD, cred, p);
 		}
+		if (vn_canvmio(uvp) == TRUE)
+			error = vfs_object_create(uvp, p, cred);
 		un->un_openl = 0;
 	}
 
@@ -728,6 +816,17 @@ union_copyup(un, docopy, cred, p)
 
 }
 
+/*
+ *	union_relookup:
+ *
+ *	dvp should be locked on entry and will be locked on return.  No
+ *	net change in the ref count will occur.
+ *
+ *	If an error is returned, *vpp will be invalid, otherwise it
+ *	will hold a locked, referenced vnode.  If *vpp == dvp then
+ *	remember that only one exclusive lock is held.
+ */
+
 static int
 union_relookup(um, dvp, vpp, cnp, cn, path, pathlen)
 	struct union_mount *um;
@@ -757,7 +856,7 @@ union_relookup(um, dvp, vpp, cnp, cn, path, pathlen)
 	cn->cn_pnbuf[cn->cn_namelen] = '\0';
 
 	cn->cn_nameiop = CREATE;
-	cn->cn_flags = (LOCKPARENT|HASBUF|SAVENAME|SAVESTART|ISLASTCN);
+	cn->cn_flags = (LOCKPARENT|LOCKLEAF|HASBUF|SAVENAME|ISLASTCN);
 	cn->cn_proc = cnp->cn_proc;
 	if (um->um_op == UNMNT_ABOVE)
 		cn->cn_cred = cnp->cn_cred;
@@ -768,15 +867,30 @@ union_relookup(um, dvp, vpp, cnp, cn, path, pathlen)
 	cn->cn_consume = cnp->cn_consume;
 
 	VREF(dvp);
-	error = relookup(dvp, vpp, cn);
-	if (!error)
-		vrele(dvp);
-	else {
+	VOP_UNLOCK(dvp, 0, cnp->cn_proc);
+
+	/*
+	 * Pass dvp unlocked and referenced on call to relookup().
+	 *
+	 * If an error occurs, dvp will be returned unlocked and dereferenced.
+	 */
+
+	if ((error = relookup(dvp, vpp, cn)) != 0) {
 		zfree(namei_zone, cn->cn_pnbuf);
 		cn->cn_pnbuf = NULL;
+		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, cnp->cn_proc);
+		return(error);
 	}
 
-	return (error);
+	/*
+	 * If no error occurs, dvp will be returned locked with the reference
+	 * left as before, and vpp will be returned referenced and locked.
+	 *
+	 * We want to return with dvp as it was passed to us, so we get
+	 * rid of our reference.
+	 */
+	vrele(dvp);
+	return (0);
 }
 
 /*
@@ -785,11 +899,11 @@ union_relookup(um, dvp, vpp, cnp, cn, path, pathlen)
  *
  * (um) points to the union mount structure for access to the
  * the mounting process's credentials.
- * (dvp) is the directory in which to create the shadow directory.
- * it is unlocked on entry and exit.
+ * (dvp) is the directory in which to create the shadow directory,
+ * it is locked (but not ref'd) on entry and return.
  * (cnp) is the componentname to be created.
  * (vpp) is the returned newly created shadow directory, which
- * is returned locked.
+ * is returned locked and ref'd
  */
 int
 union_mkshadow(um, dvp, cnp, vpp)
@@ -810,8 +924,10 @@ union_mkshadow(um, dvp, cnp, vpp)
 
 	if (*vpp) {
 		VOP_ABORTOP(dvp, &cn);
-		VOP_UNLOCK(dvp, 0, p);
-		vrele(*vpp);
+		if (dvp == *vpp)
+			vrele(*vpp);
+		else
+			vput(*vpp);
 		*vpp = NULLVP;
 		return (EEXIST);
 	}
@@ -832,7 +948,7 @@ union_mkshadow(um, dvp, cnp, vpp)
 	VOP_LEASE(dvp, p, cn.cn_cred, LEASE_WRITE);
 
 	error = VOP_MKDIR(dvp, vpp, &cn, &va);
-	vput(dvp);
+	/*vput(dvp);*/
 	return (error);
 }
 
@@ -842,7 +958,7 @@ union_mkshadow(um, dvp, cnp, vpp)
  * (um) points to the union mount structure for access to the
  * the mounting process's credentials.
  * (dvp) is the directory in which to create the whiteout.
- * it is locked on entry and exit.
+ * it is locked on entry and return.
  * (cnp) is the componentname to be created.
  */
 int
@@ -857,17 +973,16 @@ union_mkwhiteout(um, dvp, cnp, path)
 	struct vnode *wvp;
 	struct componentname cn;
 
-	VOP_UNLOCK(dvp, 0, p);
 	error = union_relookup(um, dvp, &wvp, cnp, &cn, path, strlen(path));
-	if (error) {
-		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
+	if (error)
 		return (error);
-	}
 
 	if (wvp) {
 		VOP_ABORTOP(dvp, &cn);
-		vrele(dvp);
-		vrele(wvp);
+		if (wvp == dvp)
+			vrele(wvp);
+		else
+			vput(wvp);
 		return (EEXIST);
 	}
 
@@ -877,9 +992,6 @@ union_mkwhiteout(um, dvp, cnp, path)
 	error = VOP_WHITEOUT(dvp, &cn, CREATE);
 	if (error)
 		VOP_ABORTOP(dvp, &cn);
-
-	vrele(dvp);
-
 	return (error);
 }
 
@@ -890,6 +1002,12 @@ union_mkwhiteout(um, dvp, cnp, path)
  * the problem with calling namei is that a) it locks too many
  * things, and b) it doesn't start at the "right" directory,
  * whereas relookup is told where to start.
+ *
+ * On entry, the vnode associated with un is locked.  It remains locked
+ * on return.
+ *
+ * If no error occurs, *vpp contains a locked referenced vnode for your
+ * use.  If an error occurs *vpp iis undefined.
  */
 static int
 union_vn_create(vpp, un, p)
@@ -921,26 +1039,34 @@ union_vn_create(vpp, un, p)
 	cn.cn_pnbuf = zalloc(namei_zone);
 	bcopy(un->un_path, cn.cn_pnbuf, cn.cn_namelen+1);
 	cn.cn_nameiop = CREATE;
-	cn.cn_flags = (LOCKPARENT|HASBUF|SAVENAME|SAVESTART|ISLASTCN);
+	cn.cn_flags = (LOCKPARENT|LOCKLEAF|HASBUF|SAVENAME|ISLASTCN);
 	cn.cn_proc = p;
 	cn.cn_cred = p->p_ucred;
 	cn.cn_nameptr = cn.cn_pnbuf;
 	cn.cn_hash = un->un_hash;
 	cn.cn_consume = 0;
 
+	/*
+	 * Pass dvp unlocked and referenced on call to relookup().
+	 *
+	 * If an error occurs, dvp will be returned unlocked and dereferenced.
+	 */
 	VREF(un->un_dirvp);
 	error = relookup(un->un_dirvp, &vp, &cn);
 	if (error)
 		return (error);
-	vrele(un->un_dirvp);
 
+	/*
+	 * If no error occurs, dvp will be returned locked with the reference
+	 * left as before, and vpp will be returned referenced and locked.
+	 */
 	if (vp) {
+		vput(un->un_dirvp);
 		VOP_ABORTOP(un->un_dirvp, &cn);
-		if (un->un_dirvp == vp)
-			vrele(un->un_dirvp);
+		if (vp == un->un_dirvp)
+			vrele(vp);
 		else
-			vput(un->un_dirvp);
-		vrele(vp);
+			vput(vp);
 		return (EEXIST);
 	}
 
@@ -964,11 +1090,12 @@ union_vn_create(vpp, un, p)
 		return (error);
 
 	error = VOP_OPEN(vp, fmode, cred, p);
+	if (error == 0 && vn_canvmio(vp) == TRUE)
+		error = vfs_object_create(vp, p, cred);
 	if (error) {
 		vput(vp);
 		return (error);
 	}
-
 	vp->v_writecount++;
 	*vpp = vp;
 	return (0);
@@ -987,6 +1114,14 @@ union_vn_close(vp, fmode, cred, p)
 	return (VOP_CLOSE(vp, fmode, cred, p));
 }
 
+#if 0
+
+/*
+ *	union_removed_upper:
+ *
+ *	called with union_node unlocked. XXX
+ */
+
 void
 union_removed_upper(un)
 	struct union_node *un;
@@ -999,9 +1134,7 @@ union_removed_upper(un)
 	 * union node will have neither uppervp nor lowervp.  We remove
 	 * the union node from cache, so that it will not be referrenced.
 	 */
-#if 0
 	union_newupper(un, NULLVP);
-#endif
 	if (un->un_dircache != 0) {
 		for (vpp = un->un_dircache; *vpp != NULLVP; vpp++)
 			vrele(*vpp);
@@ -1013,28 +1146,8 @@ union_removed_upper(un)
 		un->un_flags &= ~UN_CACHED;
 		LIST_REMOVE(un, un_cache);
 	}
-
-	if (un->un_flags & UN_ULOCK) {
-		un->un_flags &= ~UN_ULOCK;
-		VOP_UNLOCK(un->un_uppervp, 0, p);
-	}
 }
 
-#if 0
-struct vnode *
-union_lowervp(vp)
-	struct vnode *vp;
-{
-	struct union_node *un = VTOUNION(vp);
-
-	if ((un->un_lowervp != NULLVP) &&
-	    (vp->v_type == un->un_lowervp->v_type)) {
-		if (vget(un->un_lowervp, 0) == 0)
-			return (un->un_lowervp);
-	}
-
-	return (NULLVP);
-}
 #endif
 
 /*
@@ -1104,13 +1217,12 @@ union_dircache(vp, p)
 
 	nvp = NULLVP;
 
-	if (dircache == 0) {
+	if (dircache == NULL) {
 		cnt = 0;
 		union_dircache_r(vp, 0, &cnt);
 		cnt++;
-		dircache = (struct vnode **)
-				malloc(cnt * sizeof(struct vnode *),
-					M_TEMP, M_WAITOK);
+		dircache = malloc(cnt * sizeof(struct vnode *),
+				M_TEMP, M_WAITOK);
 		vpp = dircache;
 		union_dircache_r(vp, &vpp, &cnt);
 		*vpp = NULLVP;
@@ -1126,9 +1238,11 @@ union_dircache(vp, p)
 	if (*vpp == NULLVP)
 		goto out;
 
-	vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY, p);
+	/*vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY, p);*/
+	UDEBUG(("ALLOCVP-3 %p ref %d\n", *vpp, (*vpp ? (*vpp)->v_usecount : -99)));
 	VREF(*vpp);
-	error = union_allocvp(&nvp, vp->v_mount, NULLVP, NULLVP, 0, *vpp, NULLVP, 0);
+	error = union_allocvp(&nvp, vp->v_mount, NULLVP, NULLVP, NULL, *vpp, NULLVP, 0);
+	UDEBUG(("ALLOCVP-3B %p ref %d\n", nvp, (*vpp ? (*vpp)->v_usecount : -99)));
 	if (error)
 		goto out;
 
@@ -1142,6 +1256,40 @@ out:
 }
 
 /*
+ * Guarentee coherency with the VM cache by invalidating any clean VM pages
+ * associated with this write and updating any dirty VM pages.  Since our
+ * vnode is locked, other processes will not be able to read the pages in
+ * again until after our write completes.
+ *
+ * We also have to be coherent with reads, by flushing any pending dirty
+ * pages prior to issuing the read.
+ *
+ * XXX this is somewhat of a hack at the moment.  To support this properly
+ * we would have to be able to run VOP_READ and VOP_WRITE through the VM
+ * cache.  Then we wouldn't need to worry about coherency.
+ */
+
+void 
+union_vm_coherency(struct vnode *vp, struct uio *uio, int cleanfls)
+{
+	vm_object_t object;
+	vm_pindex_t pstart;
+	vm_pindex_t pend;
+	int pgoff;
+
+	if ((object = vp->v_object) == NULL)
+	    return;
+
+	pgoff = uio->uio_offset & PAGE_MASK;
+	pstart = uio->uio_offset / PAGE_SIZE;
+	pend = pstart + (uio->uio_resid + pgoff + PAGE_MASK) / PAGE_SIZE;
+
+	vm_object_page_clean(object, pstart, pend, OBJPC_SYNC);
+	if (cleanfls)
+		vm_object_page_remove(object, pstart, pend, TRUE);
+}
+
+/*
  * Module glue to remove #ifdef UNION from vfs_syscalls.c
  */
 static int
@@ -1169,6 +1317,8 @@ union_dircheck(struct proc *p, struct vnode **vp, struct file *fp)
 
 		if (lvp != NULLVP) {
 			error = VOP_OPEN(lvp, FREAD, fp->f_cred, p);
+			if (error == 0 && vn_canvmio(lvp) == TRUE)
+				error = vfs_object_create(lvp, p, fp->f_cred);
 			if (error) {
 				vput(lvp);
 				return (error);
@@ -1201,9 +1351,11 @@ union_modevent(module_t mod, int type, void *data)
 	}
 	return 0;
 }
+
 static moduledata_t union_mod = {
 	"union_dircheck",
 	union_modevent,
 	NULL
 };
+
 DECLARE_MODULE(union_dircheck, union_mod, SI_SUB_VFS, SI_ORDER_ANY);
diff --git a/sys/fs/unionfs/union_vfsops.c b/sys/fs/unionfs/union_vfsops.c
index af828ac64a8c..1a53f88bcc7b 100644
--- a/sys/fs/unionfs/union_vfsops.c
+++ b/sys/fs/unionfs/union_vfsops.c
@@ -85,9 +85,7 @@ union_mount(mp, path, data, ndp, p)
 	int len;
 	u_int size;
 
-#ifdef DEBUG
-	printf("union_mount(mp = %p)\n", (void *)mp);
-#endif
+	UDEBUG(("union_mount(mp = %p)\n", (void *)mp));
 
 	/*
 	 * Disable clustered write, otherwise system becomes unstable.
@@ -114,24 +112,35 @@ union_mount(mp, path, data, ndp, p)
 	if (error)
 		goto bad;
 
+	/*
+	 * Obtain lower vnode.  Vnode is stored in mp->mnt_vnodecovered.
+	 * We need to reference it but not lock it.
+	 */
+
 	lowerrootvp = mp->mnt_vnodecovered;
 	VREF(lowerrootvp);
 
+#if 0
 	/*
 	 * Unlock lower node to avoid deadlock.
 	 */
 	if (lowerrootvp->v_op == union_vnodeop_p)
 		VOP_UNLOCK(lowerrootvp, 0, p);
+#endif
 
 	/*
-	 * Find upper node.
+	 * Obtain upper vnode by calling namei() on the path.  The
+	 * upperrootvp will be turned referenced but not locked.
 	 */
 	NDINIT(ndp, LOOKUP, FOLLOW|WANTPARENT,
 	       UIO_USERSPACE, args.target, p);
 
 	error = namei(ndp);
+
+#if 0
 	if (lowerrootvp->v_op == union_vnodeop_p)
 		vn_lock(lowerrootvp, LK_EXCLUSIVE | LK_RETRY, p);
+#endif
 	if (error)
 		goto bad;
 
@@ -139,8 +148,11 @@ union_mount(mp, path, data, ndp, p)
 	vrele(ndp->ni_dvp);
 	ndp->ni_dvp = NULL;
 
+	UDEBUG(("mount_root UPPERVP %p locked = %d\n", upperrootvp, VOP_ISLOCKED(upperrootvp)));
+
 	/*
 	 * Check multi union mount to avoid `lock myself again' panic.
+	 * Also require that it be a directory.
 	 */
 	if (upperrootvp == VTOUNION(lowerrootvp)->un_uppervp) {
 #ifdef DIAGNOSTIC
@@ -155,35 +167,43 @@ union_mount(mp, path, data, ndp, p)
 		goto bad;
 	}
 
-	um = (struct union_mount *) malloc(sizeof(struct union_mount),
-				M_UNIONFSMNT, M_WAITOK);	/* XXX */
-
 	/*
-	 * Keep a held reference to the target vnodes.
-	 * They are vrele'd in union_unmount.
-	 *
-	 * Depending on the _BELOW flag, the filesystems are
-	 * viewed in a different order.  In effect, this is the
-	 * same as providing a mount under option to the mount syscall.
+	 * Allocate our union_mount structure and populate the fields.
+	 * The vnode references are stored in the union_mount as held,
+	 * unlocked references.  Depending on the _BELOW flag, the
+	 * filesystems are viewed in a different order.  In effect this
+	 * is the same as providing a mount-under option to the mount
+	 * syscall.
 	 */
 
+	um = (struct union_mount *) malloc(sizeof(struct union_mount),
+				M_UNIONFSMNT, M_WAITOK);
+
+	bzero(um, sizeof(struct union_mount));
+
 	um->um_op = args.mntflags & UNMNT_OPMASK;
+
 	switch (um->um_op) {
 	case UNMNT_ABOVE:
 		um->um_lowervp = lowerrootvp;
 		um->um_uppervp = upperrootvp;
+		upperrootvp = NULL;
+		lowerrootvp = NULL;
 		break;
 
 	case UNMNT_BELOW:
 		um->um_lowervp = upperrootvp;
 		um->um_uppervp = lowerrootvp;
+		upperrootvp = NULL;
+		lowerrootvp = NULL;
 		break;
 
 	case UNMNT_REPLACE:
 		vrele(lowerrootvp);
-		lowerrootvp = NULLVP;
+		lowerrootvp = NULL;
 		um->um_uppervp = upperrootvp;
 		um->um_lowervp = lowerrootvp;
+		upperrootvp = NULL;
 		break;
 
 	default:
@@ -196,7 +216,7 @@ union_mount(mp, path, data, ndp, p)
 	 * supports whiteout operations
 	 */
 	if ((mp->mnt_flag & MNT_RDONLY) == 0) {
-		error = VOP_WHITEOUT(um->um_uppervp, (struct componentname *) 0, LOOKUP);
+		error = VOP_WHITEOUT(um->um_uppervp, NULL, LOOKUP);
 		if (error)
 			goto bad;
 	}
@@ -258,15 +278,19 @@ union_mount(mp, path, data, ndp, p)
 
 	(void)union_statfs(mp, &mp->mnt_stat, p);
 
-#ifdef DEBUG
-	printf("union_mount: from %s, on %s\n",
-		mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
-#endif
+	UDEBUG(("union_mount: from %s, on %s\n",
+		mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname));
 	return (0);
 
 bad:
-	if (um)
+	if (um) {
+		if (um->um_uppervp)
+			vrele(um->um_uppervp);
+		if (um->um_lowervp)
+			vrele(um->um_lowervp);
+		/* XXX other fields */
 		free(um, M_UNIONFSMNT);
+	}
 	if (cred)
 		crfree(cred);
 	if (upperrootvp)
@@ -291,9 +315,7 @@ union_unmount(mp, mntflags, p)
 	int freeing;
 	int flags = 0;
 
-#ifdef DEBUG
-	printf("union_unmount(mp = %p)\n", (void *)mp);
-#endif
+	UDEBUG(("union_unmount(mp = %p)\n", (void *)mp));
 
 	if (mntflags & MNT_FORCE)
 		flags |= FORCECLOSE;
@@ -365,55 +387,25 @@ union_root(mp, vpp)
 	struct mount *mp;
 	struct vnode **vpp;
 {
-	struct proc *p = curproc;	/* XXX */
 	struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
 	int error;
-	int loselock;
-	int lockadj = 0;
-
-	if (um->um_lowervp && um->um_op != UNMNT_BELOW &&
-		VOP_ISLOCKED(um->um_lowervp)) {
-		VREF(um->um_lowervp);
-		VOP_UNLOCK(um->um_lowervp, 0, p);
-		lockadj = 1;
-	}
 
 	/*
-	 * Return locked reference to root.
+	 * Supply an unlocked reference to um_uppervp and to um_lowervp.  It
+	 * is possible for um_uppervp to be locked without the associated
+	 * root union_node being locked.  We let union_allocvp() deal with
+	 * it.
 	 */
+	UDEBUG(("union_root UPPERVP %p locked = %d\n", um->um_uppervp, VOP_ISLOCKED(um->um_uppervp)));
+
 	VREF(um->um_uppervp);
-	if ((um->um_op == UNMNT_BELOW) &&
-	    VOP_ISLOCKED(um->um_uppervp)) {
-		loselock = 1;
-	} else {
-		vn_lock(um->um_uppervp, LK_EXCLUSIVE | LK_RETRY, p);
-		loselock = 0;
-	}
 	if (um->um_lowervp)
 		VREF(um->um_lowervp);
-	error = union_allocvp(vpp, mp,
-			      (struct vnode *) 0,
-			      (struct vnode *) 0,
-			      (struct componentname *) 0,
-			      um->um_uppervp,
-			      um->um_lowervp,
-			      1);
 
-	if (error) {
-		if (loselock)
-			vrele(um->um_uppervp);
-		else
-			vput(um->um_uppervp);
-		if (um->um_lowervp)
-			vrele(um->um_lowervp);
-	} else {
-		if (loselock)
-			VTOUNION(*vpp)->un_flags &= ~UN_ULOCK;
-	}
-	if (lockadj) {
-		vn_lock(um->um_lowervp, LK_EXCLUSIVE | LK_RETRY, p);
-		vrele(um->um_lowervp);
-	}
+	error = union_allocvp(vpp, mp, NULLVP, NULLVP, NULL, 
+		    um->um_uppervp, um->um_lowervp, 1);
+	UDEBUG(("error %d\n", error));
+	UDEBUG(("union_root2 UPPERVP %p locked = %d\n", um->um_uppervp, VOP_ISLOCKED(um->um_uppervp)));
 
 	return (error);
 }
@@ -429,10 +421,8 @@ union_statfs(mp, sbp, p)
 	struct statfs mstat;
 	int lbsize;
 
-#ifdef DEBUG
-	printf("union_statfs(mp = %p, lvp = %p, uvp = %p)\n",
-	    (void *)mp, (void *)um->um_lowervp, (void *)um->um_uppervp);
-#endif
+	UDEBUG(("union_statfs(mp = %p, lvp = %p, uvp = %p)\n",
+	    (void *)mp, (void *)um->um_lowervp, (void *)um->um_uppervp));
 
 	bzero(&mstat, sizeof(mstat));
 
diff --git a/sys/fs/unionfs/union_vnops.c b/sys/fs/unionfs/union_vnops.c
index 145f8ca6f0ad..128e59ebaa21 100644
--- a/sys/fs/unionfs/union_vnops.c
+++ b/sys/fs/unionfs/union_vnops.c
@@ -50,13 +50,25 @@
 #include <sys/malloc.h>
 #include <sys/buf.h>
 #include <sys/lock.h>
+#include <sys/sysctl.h>
 #include <miscfs/union/union.h>
 
-#define FIXUP(un, p) { \
-	if (((un)->un_flags & UN_ULOCK) == 0) { \
-		union_fixup(un, p); \
-	} \
-}
+#include <vm/vm.h>
+#include <vm/vnode_pager.h>
+
+#include <vm/vm_prot.h>
+#include <vm/vm_page.h>
+#include <vm/vm_object.h>
+#include <vm/vm_pager.h>
+#include <vm/vm_extern.h>
+
+int uniondebug = 0;
+
+#if UDEBUG_ENABLED
+SYSCTL_INT(_vfs, OID_AUTO, uniondebug, CTLFLAG_RW, &uniondebug, 0, "");
+#else
+SYSCTL_INT(_vfs, OID_AUTO, uniondebug, CTLFLAG_RD, &uniondebug, 0, "");
+#endif
 
 static int	union_abortop __P((struct vop_abortop_args *ap));
 static int	union_access __P((struct vop_access_args *ap));
@@ -64,17 +76,15 @@ static int	union_advlock __P((struct vop_advlock_args *ap));
 static int	union_bmap __P((struct vop_bmap_args *ap));
 static int	union_close __P((struct vop_close_args *ap));
 static int	union_create __P((struct vop_create_args *ap));
-static void	union_fixup __P((struct union_node *un, struct proc *p));
 static int	union_fsync __P((struct vop_fsync_args *ap));
 static int	union_getattr __P((struct vop_getattr_args *ap));
 static int	union_inactive __P((struct vop_inactive_args *ap));
 static int	union_ioctl __P((struct vop_ioctl_args *ap));
-static int	union_islocked __P((struct vop_islocked_args *ap));
 static int	union_lease __P((struct vop_lease_args *ap));
 static int	union_link __P((struct vop_link_args *ap));
 static int	union_lock __P((struct vop_lock_args *ap));
 static int	union_lookup __P((struct vop_lookup_args *ap));
-static int	union_lookup1 __P((struct vnode *udvp, struct vnode **dvpp,
+static int	union_lookup1 __P((struct vnode *udvp, struct vnode **dvp,
 				   struct vnode **vpp,
 				   struct componentname *cnp));
 static int	union_mkdir __P((struct vop_mkdir_args *ap));
@@ -94,36 +104,89 @@ static int	union_rmdir __P((struct vop_rmdir_args *ap));
 static int	union_poll __P((struct vop_poll_args *ap));
 static int	union_setattr __P((struct vop_setattr_args *ap));
 static int	union_strategy __P((struct vop_strategy_args *ap));
+static int	union_getpages __P((struct vop_getpages_args *ap));
+static int	union_putpages __P((struct vop_putpages_args *ap));
 static int	union_symlink __P((struct vop_symlink_args *ap));
 static int	union_unlock __P((struct vop_unlock_args *ap));
 static int	union_whiteout __P((struct vop_whiteout_args *ap));
 static int	union_write __P((struct vop_read_args *ap));
 
-static void
-union_fixup(un, p)
-	struct union_node *un;
-	struct proc *p;
+static __inline
+struct vnode *
+union_lock_upper(struct union_node *un, struct proc *p)
 {
+	struct vnode *uppervp;
+
+	if ((uppervp = un->un_uppervp) != NULL) {
+		VREF(uppervp);
+		vn_lock(uppervp, LK_EXCLUSIVE | LK_CANRECURSE | LK_RETRY, p);
+	}
+	KASSERT((uppervp == NULL || uppervp->v_usecount > 0), ("uppervp usecount is 0"));
+	return(uppervp);
+}
+
+static __inline
+void
+union_unlock_upper(struct vnode *uppervp, struct proc *p)
+{
+	vput(uppervp);
+}
+
+static __inline
+struct vnode *
+union_lock_other(struct union_node *un, struct proc *p)
+{
+	struct vnode *vp;
 
-	vn_lock(un->un_uppervp, LK_EXCLUSIVE | LK_RETRY, p);
-	un->un_flags |= UN_ULOCK;
+	if (un->un_uppervp != NULL) {
+		vp = union_lock_upper(un, p);
+	} else if ((vp = un->un_lowervp) != NULL) {
+		VREF(vp);
+		vn_lock(vp, LK_EXCLUSIVE | LK_CANRECURSE | LK_RETRY, p);
+	}
+	return(vp);
+}
+
+static __inline
+void
+union_unlock_other(struct vnode *vp, struct proc *p)
+{
+	vput(vp);
 }
 
+/*
+ *	union_lookup:
+ *
+ *	udvp	must be exclusively locked on call and will remain 
+ *		exclusively locked on return.  This is the mount point 
+ *		for out filesystem.
+ *
+ *	dvp	Our base directory, locked and referenced.
+ *		The passed dvp will be dereferenced and unlocked on return
+ *		and a new dvp will be returned which is locked and 
+ *		referenced in the same variable.
+ *
+ *	vpp	is filled in with the result if no error occured,
+ *		locked and ref'd.
+ *
+ *		If an error is returned, *vpp is set to NULLVP.  If no
+ *		error occurs, *vpp is returned with a reference and an
+ *		exclusive lock.
+ */
+
 static int
-union_lookup1(udvp, dvpp, vpp, cnp)
+union_lookup1(udvp, pdvp, vpp, cnp)
 	struct vnode *udvp;
-	struct vnode **dvpp;
+	struct vnode **pdvp;
 	struct vnode **vpp;
 	struct componentname *cnp;
 {
 	int error;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *dvp = *pdvp;
 	struct vnode *tdvp;
-	struct vnode *dvp;
 	struct mount *mp;
 
-	dvp = *dvpp;
-
 	/*
 	 * If stepping up the directory tree, check for going
 	 * back across the mount point, in which case do what
@@ -139,49 +202,79 @@ union_lookup1(udvp, dvpp, vpp, cnp)
 			 * filesystems.
 			 */
 			tdvp = dvp;
-			*dvpp = dvp = dvp->v_mount->mnt_vnodecovered;
-			vput(tdvp);
+			dvp = dvp->v_mount->mnt_vnodecovered;
 			VREF(dvp);
+			vput(tdvp);
 			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
 		}
 	}
 
+	/*
+	 * Set return dvp to be the upperdvp 'parent directory.
+	 */
+	*pdvp = dvp;
+
+	/*
+	 * If the VOP_LOOKUP call generates an error, tdvp is invalid and no
+	 * changes will have been made to dvp, so we are set to return.
+	 */
+
         error = VOP_LOOKUP(dvp, &tdvp, cnp);
-	if (error)
+	if (error) {
+		UDEBUG(("dvp %p error %d flags %lx\n", dvp, error, cnp->cn_flags));
+		*vpp = NULL;
 		return (error);
+	}
 
 	/*
 	 * The parent directory will have been unlocked, unless lookup
-	 * found the last component.  In which case, re-lock the node
-	 * here to allow it to be unlocked again (phew) in union_lookup.
+	 * found the last component or if dvp == tdvp (tdvp must be locked).
+	 *
+	 * We want our dvp to remain locked and ref'd.  We also want tdvp
+	 * to remain locked and ref'd.
 	 */
-	if (dvp != tdvp && !(cnp->cn_flags & ISLASTCN))
-		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
+	UDEBUG(("parentdir %p result %p flag %lx\n", dvp, tdvp, cnp->cn_flags));
 
-	dvp = tdvp;
+	if (dvp != tdvp && (cnp->cn_flags & ISLASTCN) == 0)
+		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
 
 	/*
 	 * Lastly check if the current node is a mount point in
 	 * which case walk up the mount hierarchy making sure not to
 	 * bump into the root of the mount tree (ie. dvp != udvp).
+	 *
+	 * We use dvp as a temporary variable here, it is no longer related
+	 * to the dvp above.  However, we have to ensure that both *pdvp and
+	 * tdvp are locked on return.
 	 */
-	while (dvp != udvp && (dvp->v_type == VDIR) &&
-	       (mp = dvp->v_mountedhere)) {
+
+	dvp = tdvp;
+	while (
+	    dvp != udvp && 
+	    (dvp->v_type == VDIR) &&
+	    (mp = dvp->v_mountedhere)
+	) {
+		int relock_pdvp = 0;
 
 		if (vfs_busy(mp, 0, 0, p))
 			continue;
 
-		error = VFS_ROOT(mp, &tdvp);
+		if (dvp == *pdvp)
+			relock_pdvp = 1;
+		vput(dvp);
+		dvp = NULL;
+		error = VFS_ROOT(mp, &dvp);
+
 		vfs_unbusy(mp, p);
+
+		if (relock_pdvp)
+			vn_lock(*pdvp, LK_EXCLUSIVE | LK_RETRY, p);
+
 		if (error) {
-			vput(dvp);
+			*vpp = NULL;
 			return (error);
 		}
-
-		vput(dvp);
-		dvp = tdvp;
 	}
-
 	*vpp = dvp;
 	return (0);
 }
@@ -199,8 +292,8 @@ union_lookup(ap)
 	int uerror, lerror;
 	struct vnode *uppervp, *lowervp;
 	struct vnode *upperdvp, *lowerdvp;
-	struct vnode *dvp = ap->a_dvp;
-	struct union_node *dun = VTOUNION(dvp);
+	struct vnode *dvp = ap->a_dvp;		/* starting dir */
+	struct union_node *dun = VTOUNION(dvp);	/* associated union node */
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
 	int lockparent = cnp->cn_flags & LOCKPARENT;
@@ -209,44 +302,38 @@ union_lookup(ap)
 	int iswhiteout;
 	struct vattr va;
 
+	*ap->a_vpp = NULLVP;
 
 	/*
 	 * Disallow write attemps to the filesystem mounted read-only.
 	 */
-	if ((cnp->cn_flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
-		(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
+	if ((cnp->cn_flags & ISLASTCN) && 
+	    (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
+	    (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
 		return (EROFS);
-
-#ifdef notyet
-	if (cnp->cn_namelen == 3 &&
-			cnp->cn_nameptr[2] == '.' &&
-			cnp->cn_nameptr[1] == '.' &&
-			cnp->cn_nameptr[0] == '.') {
-		dvp = *ap->a_vpp = LOWERVP(ap->a_dvp);
-		if (dvp == NULLVP)
-			return (ENOENT);
-		VREF(dvp);
-		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
-		if (!lockparent || !(cnp->cn_flags & ISLASTCN))
-			VOP_UNLOCK(ap->a_dvp, 0, p);
-		return (0);
 	}
-#endif
 
+	/*
+	 * For any lookup's we do, always return with the parent locked
+	 */
 	cnp->cn_flags |= LOCKPARENT;
 
-	upperdvp = dun->un_uppervp;
 	lowerdvp = dun->un_lowervp;
 	uppervp = NULLVP;
 	lowervp = NULLVP;
 	iswhiteout = 0;
 
-	if (cnp->cn_flags & ISDOTDOT) {
-		if (upperdvp != NULL)
-			VREF(upperdvp);
-		if (lowerdvp != NULL)
-			VREF(lowerdvp);
-	}
+	uerror = ENOENT;
+	lerror = ENOENT;
+
+	/*
+	 * Get a private lock on uppervp and a reference, effectively 
+	 * taking it out of the union_node's control.
+	 *
+	 * We must lock upperdvp while holding our lock on dvp
+	 * to avoid a deadlock.
+	 */
+	upperdvp = union_lock_upper(dun, p);
 
 	/*
 	 * do the lookup in the upper level.
@@ -255,62 +342,64 @@ union_lookup(ap)
 	 * on and just return that vnode.
 	 */
 	if (upperdvp != NULLVP) {
-		FIXUP(dun, p);
 		/*
-		 * If we're doing `..' in the underlying filesystem,
-		 * we must drop our lock on the union node before
-		 * going up the tree in the lower file system--if we block
-		 * on the lowervp lock, and that's held by someone else
-		 * coming down the tree and who's waiting for our lock,
-		 * we would be hosed.
+		 * We do not have to worry about the DOTDOT case, we've
+		 * already unlocked dvp.
 		 */
-		if (cnp->cn_flags & ISDOTDOT) {
-			/* retain lock on underlying VP: */
-			dun->un_flags |= UN_KLOCK;
-			VOP_UNLOCK(dvp, 0, p);
-		}
-		uerror = union_lookup1(um->um_uppervp, &upperdvp,
-					&uppervp, cnp);
+		UDEBUG(("A %p\n", upperdvp));
+
+		/*
+		 * Do the lookup.   We must supply a locked and referenced
+		 * upperdvp to the function and will get a new locked and
+		 * referenced upperdvp back with the old having been 
+		 * dereferenced.
+		 *
+		 * If an error is returned, uppervp will be NULLVP.  If no
+		 * error occurs, uppervp will be the locked and referenced
+		 * return vnode or possibly NULL, depending on what is being
+		 * requested.  It is possible that the returned uppervp
+		 * will be the same as upperdvp.
+		 */
+		uerror = union_lookup1(um->um_uppervp, &upperdvp, &uppervp, cnp);
+		UDEBUG((
+		    "uerror %d upperdvp %p %d/%d, uppervp %p ref=%d/lck=%d\n",
+		    uerror,
+		    upperdvp,
+		    upperdvp->v_usecount,
+		    VOP_ISLOCKED(upperdvp),
+		    uppervp,
+		    (uppervp ? uppervp->v_usecount : -99),
+		    (uppervp ? VOP_ISLOCKED(uppervp) : -99)
+		));
+
 		/*
 		 * Disallow write attemps to the filesystem mounted read-only.
 		 */
 		if (uerror == EJUSTRETURN && (cnp->cn_flags & ISLASTCN) &&
-			(dvp->v_mount->mnt_flag & MNT_RDONLY) &&
-			(cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME)) {
-			if (!lockparent)
-				cnp->cn_flags &= ~LOCKPARENT;
-			return (EROFS);
-		}
-			
-		if (cnp->cn_flags & ISDOTDOT) {
-			if (dun->un_uppervp == upperdvp) {
-				/*
-				 * We got the underlying bugger back locked...
-				 * now take back the union node lock.  Since we
-				 * hold the uppervp lock, we can diddle union
-				 * locking flags at will. :)
-				 */
-				dun->un_flags |= UN_ULOCK;
-			}
-			/*
-			 * If upperdvp got swapped out, it means we did
-			 * some mount point magic, and we do not have
-			 * dun->un_uppervp locked currently--so we get it
-			 * locked here (don't set the UN_ULOCK flag).
-			 */
-			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
+		    (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
+		    (cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME)) {
+			error = EROFS;
+			goto out;
 		}
 
-		/*if (uppervp == upperdvp)
-			dun->un_flags |= UN_KLOCK;*/
+		/*
+		 * Special case.  If cn_consume != 0 skip out.  The result
+		 * of the lookup is transfered to our return variable.  If
+		 * an error occured we have to throw away the results.
+		 */
 
 		if (cnp->cn_consume != 0) {
-			*ap->a_vpp = uppervp;
-			if (!lockparent)
-				cnp->cn_flags &= ~LOCKPARENT;
-			error = uerror;
+			if ((error = uerror) == 0) {
+				*ap->a_vpp = uppervp;
+				uppervp = NULL;
+			}
 			goto out;
 		}
+
+		/*
+		 * Calculate whiteout, fall through
+		 */
+
 		if (uerror == ENOENT || uerror == EJUSTRETURN) {
 			if (cnp->cn_flags & ISWHITEOUT) {
 				iswhiteout = 1;
@@ -321,8 +410,6 @@ union_lookup(ap)
 					iswhiteout = 1;
 			}
 		}
-	} else {
-		uerror = ENOENT;
 	}
 
 	/*
@@ -332,13 +419,14 @@ union_lookup(ap)
 	 * back from the upper layer and return the lower vnode
 	 * instead.
 	 */
+
 	if (lowerdvp != NULLVP && !iswhiteout) {
 		int nameiop;
 
-		vn_lock(lowerdvp, LK_EXCLUSIVE | LK_RETRY, p);
+		UDEBUG(("B %p\n", lowerdvp));
 
 		/*
-		 * Only do a LOOKUP on the bottom node, since
+		 * Force only LOOKUPs on the lower node, since
 		 * we won't be making changes to it anyway.
 		 */
 		nameiop = cnp->cn_nameiop;
@@ -347,42 +435,42 @@ union_lookup(ap)
 			saved_cred = cnp->cn_cred;
 			cnp->cn_cred = um->um_cred;
 		}
+
 		/*
 		 * We shouldn't have to worry about locking interactions
 		 * between the lower layer and our union layer (w.r.t.
 		 * `..' processing) because we don't futz with lowervp
 		 * locks in the union-node instantiation code path.
+		 *
+		 * union_lookup1() requires lowervp to be locked on entry,
+		 * and it will be unlocked on return.  The ref count will
+		 * not change.  On return lowervp doesn't represent anything
+		 * to us so we NULL it out.
 		 */
-		lerror = union_lookup1(um->um_lowervp, &lowerdvp,
-				&lowervp, cnp);
+		VREF(lowerdvp);
+		vn_lock(lowerdvp, LK_EXCLUSIVE | LK_RETRY, p);
+		lerror = union_lookup1(um->um_lowervp, &lowerdvp, &lowervp, cnp);
+		if (lowerdvp == lowervp)
+			vrele(lowerdvp);
+		else
+			vput(lowerdvp);
+		lowerdvp = NULL;	/* lowerdvp invalid after vput */
+
 		if (um->um_op == UNMNT_BELOW)
 			cnp->cn_cred = saved_cred;
 		cnp->cn_nameiop = nameiop;
 
-		if (lowervp != lowerdvp)
-			VOP_UNLOCK(lowerdvp, 0, p);
-
 		if (cnp->cn_consume != 0 || lerror == EACCES) {
-			if (lerror == EACCES)
-				lowervp = NULLVP;
-			if (uppervp != NULLVP) {
-				if (uppervp == upperdvp)
-					vrele(uppervp);
-				else
-					vput(uppervp);
-				uppervp = NULLVP;
+			if ((error = lerror) == 0) {
+				*ap->a_vpp = lowervp;
+				lowervp = NULL;
 			}
-			*ap->a_vpp = lowervp;
-			if (!lockparent)
-				cnp->cn_flags &= ~LOCKPARENT;
-			error = lerror;
 			goto out;
 		}
 	} else {
-		lerror = ENOENT;
+		UDEBUG(("C %p\n", lowerdvp));
 		if ((cnp->cn_flags & ISDOTDOT) && dun->un_pvp != NULLVP) {
-			lowervp = LOWERVP(dun->un_pvp);
-			if (lowervp != NULLVP) {
+			if ((lowervp = LOWERVP(dun->un_pvp)) != NULL) {
 				VREF(lowervp);
 				vn_lock(lowervp, LK_EXCLUSIVE | LK_RETRY, p);
 				lerror = 0;
@@ -390,35 +478,27 @@ union_lookup(ap)
 		}
 	}
 
-	if (!lockparent)
-		cnp->cn_flags &= ~LOCKPARENT;
-
 	/*
-	 * at this point, we have uerror and lerror indicating
-	 * possible errors with the lookups in the upper and lower
-	 * layers.  additionally, uppervp and lowervp are (locked)
-	 * references to existing vnodes in the upper and lower layers.
+	 * Ok.  Now we have uerror, uppervp, upperdvp, lerror, and lowervp.
+	 *
+	 * 1. If both layers returned an error, select the upper layer.
 	 *
-	 * there are now three cases to consider.
-	 * 1. if both layers returned an error, then return whatever
-	 *    error the upper layer generated.
+	 * 2. If the upper layer faile and the bottom layer succeeded,
+	 *    two subcases occur:
 	 *
-	 * 2. if the top layer failed and the bottom layer succeeded
-	 *    then two subcases occur.
-	 *    a.  the bottom vnode is not a directory, in which
-	 *	  case just return a new union vnode referencing
-	 *	  an empty top layer and the existing bottom layer.
-	 *    b.  the bottom vnode is a directory, in which case
-	 *	  create a new directory in the top-level and
-	 *	  continue as in case 3.
+	 *	a.  The bottom vnode is not a directory, in which case
+	 *	    just return a new union vnode referencing an
+	 *	    empty top layer and the existing bottom layer.
 	 *
-	 * 3. if the top layer succeeded then return a new union
+	 *	b.  The button vnode is a directory, in which case
+	 *	    create a new directory in the top layer and
+	 *	    and fall through to case 3.
+	 *
+	 * 3. If the top layer succeeded then return a new union
 	 *    vnode referencing whatever the new top layer and
 	 *    whatever the bottom layer returned.
 	 */
 
-	*ap->a_vpp = NULLVP;
-
 	/* case 1. */
 	if ((uerror != 0) && (lerror != 0)) {
 		error = uerror;
@@ -428,59 +508,126 @@ union_lookup(ap)
 	/* case 2. */
 	if (uerror != 0 /* && (lerror == 0) */ ) {
 		if (lowervp->v_type == VDIR) { /* case 2b. */
-			dun->un_flags &= ~UN_ULOCK;
-			VOP_UNLOCK(upperdvp, 0, p);
+			KASSERT(uppervp == NULL, ("uppervp unexpectedly non-NULL"));
+			/*
+			 * oops, uppervp has a problem, we may have to shadow.
+			 */
 			uerror = union_mkshadow(um, upperdvp, cnp, &uppervp);
-			vn_lock(upperdvp, LK_EXCLUSIVE | LK_RETRY, p);
-			dun->un_flags |= UN_ULOCK;
-
 			if (uerror) {
-				if (lowervp != NULLVP) {
-					vput(lowervp);
-					lowervp = NULLVP;
-				}
 				error = uerror;
 				goto out;
 			}
 		}
 	}
 
-	if (lowervp != NULLVP)
+	/*
+	 * Must call union_allocvp with both the upper and lower vnodes
+	 * referenced and the upper vnode locked.   ap->a_vpp is returned 
+	 * referenced and locked.  lowervp, uppervp, and upperdvp are 
+	 * absorbed by union_allocvp() whether it succeeds or fails.
+	 *
+	 * upperdvp is the parent directory of uppervp which may be
+	 * different, depending on the path, from dvp->un_uppervp.  That's
+	 * why it is a separate argument.  Note that it must be unlocked.
+	 *
+	 * dvp must be locked on entry to the call and will be locked on
+	 * return.
+	 */
+
+	if (uppervp && uppervp != upperdvp)
+		VOP_UNLOCK(uppervp, 0, p);
+	if (lowervp)
 		VOP_UNLOCK(lowervp, 0, p);
+	if (upperdvp)
+		VOP_UNLOCK(upperdvp, 0, p);
 
 	error = union_allocvp(ap->a_vpp, dvp->v_mount, dvp, upperdvp, cnp,
 			      uppervp, lowervp, 1);
 
-	if (error) {
-		if (uppervp != NULLVP)
-			vput(uppervp);
-		if (lowervp != NULLVP)
-			vrele(lowervp);
-	} else {
-		if (*ap->a_vpp != dvp)
-			if (!lockparent || !(cnp->cn_flags & ISLASTCN))
-				VOP_UNLOCK(dvp, 0, p);
-#ifdef DIAGNOSTIC
-        if (cnp->cn_namelen == 1 &&
-            cnp->cn_nameptr[0] == '.' &&
-            *ap->a_vpp != dvp) {
-            panic("union_lookup returning . (%p) not same as startdir (%p)",
-				  ap->a_vpp, dvp);
+	UDEBUG(("Create %p = %p %p refs=%d\n", *ap->a_vpp, uppervp, lowervp, (*ap->a_vpp) ? ((*ap->a_vpp)->v_usecount) : -99));
+
+	uppervp = NULL;
+	upperdvp = NULL;
+	lowervp = NULL;
+
+	/* 
+	 *	Termination Code
+	 *
+	 *	- put away any extra junk laying around.  Note that lowervp
+	 *	  (if not NULL) will never be the same as *ap->a_vp and 
+	 *	  neither will uppervp, because when we set that state we 
+	 *	  NULL-out lowervp or uppervp.  On the otherhand, upperdvp
+	 *	  may match uppervp or *ap->a_vpp.
+	 *
+	 *	- relock/unlock dvp if appropriate.
+	 */
+
+out:
+	if (upperdvp) {
+		if (upperdvp == uppervp || upperdvp == *ap->a_vpp)
+			vrele(upperdvp);
+		else
+			vput(upperdvp);
+	}
+
+	if (uppervp)
+		vput(uppervp);
+
+	if (lowervp)
+		vput(lowervp);
+
+	/*
+	 * Restore LOCKPARENT state
+	 */
+
+	if (!lockparent)
+		cnp->cn_flags &= ~LOCKPARENT;
+
+	UDEBUG(("Out %d vpp %p/%d lower %p upper %p\n", error, *ap->a_vpp,
+		((*ap->a_vpp) ? (*ap->a_vpp)->v_usecount : -99),
+		lowervp, uppervp));
+
+	/*
+	 * dvp lock state, determine whether to relock dvp.  dvp is expected
+	 * to be locked on return if:
+	 *
+	 *	- there was an error (except not EJUSTRETURN), or
+	 *	- we hit the last component and lockparent is true
+	 *
+	 * dvp_is_locked is the current state of the dvp lock, not counting
+	 * the possibility that *ap->a_vpp == dvp (in which case it is locked
+	 * anyway).  Note that *ap->a_vpp == dvp only if no error occured.
+	 */
+
+	if (*ap->a_vpp != dvp) {
+		if ((error == 0 || error == EJUSTRETURN) &&
+		    (!lockparent || (cnp->cn_flags & ISLASTCN) == 0)) {
+			VOP_UNLOCK(dvp, 0, p);
 		}
-#endif
 	}
 
-out:
-    if (cnp->cn_flags & ISDOTDOT) {
-        if (upperdvp != NULL)
-            vrele(upperdvp);
-        if (lowerdvp != NULL)
-            vrele(lowerdvp);
-    }
+	/*
+	 * Diagnostics
+	 */
+
+#ifdef DIAGNOSTIC
+	if (cnp->cn_namelen == 1 &&
+	    cnp->cn_nameptr[0] == '.' &&
+	    *ap->a_vpp != dvp) {
+		panic("union_lookup returning . (%p) not same as startdir (%p)", ap->a_vpp, dvp);
+	}
+#endif
 
 	return (error);
 }
 
+/*
+ * 	union_create:
+ *
+ * a_dvp is locked on entry and remains locked on return.  a_vpp is returned
+ * locked if no error occurs, otherwise it is garbage.
+ */
+
 static int
 union_create(ap)
 	struct vop_create_args /* {
@@ -491,36 +638,27 @@ union_create(ap)
 	} */ *ap;
 {
 	struct union_node *dun = VTOUNION(ap->a_dvp);
-	struct vnode *dvp = dun->un_uppervp;
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *dvp;
+	int error = EROFS;
 
-	if (dvp != NULLVP) {
+	if ((dvp = union_lock_upper(dun, p)) != NULL) {
 		struct vnode *vp;
 		struct mount *mp;
-		int error;
 
-		FIXUP(dun, p);
-
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
 		error = VOP_CREATE(dvp, &vp, cnp, ap->a_vap);
-		if (error) {
-			dun->un_flags |= UN_ULOCK;
-			return (error);
+		if (error == 0) {
+			mp = ap->a_dvp->v_mount;
+			VOP_UNLOCK(vp, 0, p);
+			UDEBUG(("ALLOCVP-1 FROM %p REFS %d\n", vp, vp->v_usecount));
+			error = union_allocvp(ap->a_vpp, mp, NULLVP, NULLVP,
+				cnp, vp, NULLVP, 1);
+			UDEBUG(("ALLOCVP-2B FROM %p REFS %d\n", *ap->a_vpp, vp->v_usecount));
 		}
-
-		mp = ap->a_dvp->v_mount;
-		VOP_UNLOCK(dvp, 0, p);
-		error = union_allocvp(ap->a_vpp, mp, NULLVP, NULLVP, cnp, vp,
-				NULLVP, 1);
-		if (error)
-			vput(vp);
-		vn_lock(ap->a_dvp, LK_EXCLUSIVE| LK_RETRY, p);
-		return (error);
+		union_unlock_upper(dvp, p);
 	}
-
-	return (EROFS);
+	return (error);
 }
 
 static int
@@ -533,15 +671,23 @@ union_whiteout(ap)
 {
 	struct union_node *un = VTOUNION(ap->a_dvp);
 	struct componentname *cnp = ap->a_cnp;
-	struct proc *p = cnp->cn_proc;
-
-	if (un->un_uppervp == NULLVP)
-		return (EOPNOTSUPP);
+	struct vnode *uppervp;
+	int error = EOPNOTSUPP;
 
-	FIXUP(un, p);
-	return (VOP_WHITEOUT(un->un_uppervp, cnp, ap->a_flags));
+	if ((uppervp = union_lock_upper(un, cnp->cn_proc)) != NULLVP) {
+		error = VOP_WHITEOUT(un->un_uppervp, cnp, ap->a_flags);
+		union_unlock_upper(uppervp, cnp->cn_proc);
+	}
+	return(error);
 }
 
+/*
+ * 	union_mknod:
+ *
+ *	a_dvp is locked on entry and should remain locked on return.
+ *	a_vpp is garbagre whether an error occurs or not.
+ */
+
 static int
 union_mknod(ap)
 	struct vop_mknod_args /* {
@@ -552,42 +698,28 @@ union_mknod(ap)
 	} */ *ap;
 {
 	struct union_node *dun = VTOUNION(ap->a_dvp);
-	struct vnode *dvp = dun->un_uppervp;
 	struct componentname *cnp = ap->a_cnp;
-	struct proc *p = cnp->cn_proc;
+	struct vnode *dvp;
+	int error = EROFS;
 
-	if (dvp != NULLVP) {
+	if ((dvp = union_lock_upper(dun, cnp->cn_proc)) != NULL) {
 		struct vnode *vp;
-		struct mount *mp;
-		int error;
-
-		FIXUP(dun, p);
-
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
 		error = VOP_MKNOD(dvp, &vp, cnp, ap->a_vap);
-		if (error) {
-			dun->un_flags |= UN_ULOCK;
-			return (error);
-		}
-
-		if (vp != NULLVP) {
-			mp = ap->a_dvp->v_mount;
-			VOP_UNLOCK(dvp, 0, p);
-			error = union_allocvp(ap->a_vpp, mp, NULLVP, NULLVP,
-					cnp, vp, NULLVP, 1);
-			if (error)
-				vput(vp);
-			vn_lock(ap->a_dvp, LK_EXCLUSIVE| LK_RETRY, p);
-		} else {
-			dun->un_flags |= UN_ULOCK;
-		}
-		return (error);
+		/* vp is garbage whether an error occurs or not */
+		union_unlock_upper(dvp, cnp->cn_proc);
 	}
-
-	return (EROFS);
+	return (error);
 }
 
+/*
+ *	union_open:
+ *
+ *	run open VOP.  When opening the underlying vnode we have to mimic
+ *	vn_open.  What we *really* need to do to avoid screwups if the
+ *	open semantics change is to call vn_open().  For example, ufs blows
+ *	up if you open a file but do not vmio it prior to writing.
+ */
+
 static int
 union_open(ap)
 	struct vop_open_args /* {
@@ -603,13 +735,18 @@ union_open(ap)
 	int mode = ap->a_mode;
 	struct ucred *cred = ap->a_cred;
 	struct proc *p = ap->a_p;
-	int error;
+	int error = 0;
+	int tvpisupper = 1;
 
 	/*
 	 * If there is an existing upper vp then simply open that.
+	 * The upper vp takes precedence over the lower vp.  When opening
+	 * a lower vp for writing copy it to the uppervp and then open the
+	 * uppervp.
+	 *
+	 * At the end of this section tvp will be left locked.
 	 */
-	tvp = un->un_uppervp;
-	if (tvp == NULLVP) {
+	if ((tvp = union_lock_upper(un, p)) == NULLVP) {
 		/*
 		 * If the lower vnode is being opened for writing, then
 		 * copy the file contents to the upper vnode and open that,
@@ -617,30 +754,50 @@ union_open(ap)
 		 */
 		tvp = un->un_lowervp;
 		if ((ap->a_mode & FWRITE) && (tvp->v_type == VREG)) {
-			error = union_copyup(un, (mode&O_TRUNC) == 0, cred, p);
-			if (error == 0)
-				error = VOP_OPEN(un->un_uppervp, mode, cred, p);
-			return (error);
+			int docopy = !(mode & O_TRUNC);
+			error = union_copyup(un, docopy, cred, p);
+			tvp = union_lock_upper(un, p);
+		} else {
+			un->un_openl++;
+			VREF(tvp);
+			vn_lock(tvp, LK_EXCLUSIVE | LK_RETRY, p);
+			tvpisupper = 0;
 		}
-
-		/*
-		 * Just open the lower vnode
-		 */
-		un->un_openl++;
-		vn_lock(tvp, LK_EXCLUSIVE | LK_RETRY, p);
-		error = VOP_OPEN(tvp, mode, cred, p);
-		VOP_UNLOCK(tvp, 0, p);
-
-		return (error);
 	}
 
-	FIXUP(un, p);
+	/*
+	 * We are holding the correct vnode, open it
+	 */
 
-	error = VOP_OPEN(tvp, mode, cred, p);
+	if (error == 0)
+		error = VOP_OPEN(tvp, mode, cred, p);
 
+	/*
+	 * Absolutely necessary or UFS will blowup
+	 */
+        if (error == 0 && vn_canvmio(tvp) == TRUE) {
+                error = vfs_object_create(tvp, p, cred);
+        }
+
+	/*
+	 * Release any locks held
+	 */
+	if (tvpisupper) {
+		if (tvp)
+			union_unlock_upper(tvp, p);
+	} else {
+		vput(tvp);
+	}
 	return (error);
 }
 
+/*
+ *	union_close:
+ *
+ *	It is unclear whether a_vp is passed locked or unlocked.  Whatever
+ *	the case we do not change it.
+ */
+
 static int
 union_close(ap)
 	struct vop_close_args /* {
@@ -661,7 +818,6 @@ union_close(ap)
 		--un->un_openl;
 		vp = un->un_lowervp;
 	}
-
 	ap->a_vp = vp;
 	return (VCALL(vp, VOFFSET(vop_close), ap));
 }
@@ -688,12 +844,12 @@ union_access(ap)
 	struct proc *p = ap->a_p;
 	int error = EACCES;
 	struct vnode *vp;
-	struct vnode *savedvp;
 
 	/*
 	 * Disallow write attempts on filesystems mounted read-only.
 	 */
-	if (ap->a_mode & VWRITE && (ap->a_vp->v_mount->mnt_flag & MNT_RDONLY)) {
+	if ((ap->a_mode & VWRITE) && 
+	    (ap->a_vp->v_mount->mnt_flag & MNT_RDONLY)) {
 		switch (ap->a_vp->v_type) {
 		case VREG: 
 		case VDIR:
@@ -703,19 +859,30 @@ union_access(ap)
 			break;
 		}
 	}
-	if ((vp = un->un_uppervp) != NULLVP) {
-		FIXUP(un, p);
+
+	if ((vp = union_lock_upper(un, p)) != NULLVP) {
 		ap->a_vp = vp;
-		return (VCALL(vp, VOFFSET(vop_access), ap));
+		error = VCALL(vp, VOFFSET(vop_access), ap);
+		union_unlock_upper(vp, p);
+		return(error);
 	}
 
 	if ((vp = un->un_lowervp) != NULLVP) {
 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-		savedvp = ap->a_vp;
 		ap->a_vp = vp;
+
+		/*
+		 * Remove VWRITE from a_mode if our mount point is RW, because
+		 * we want to allow writes and lowervp may be read-only.
+		 */
+		if ((un->un_vnode->v_mount->mnt_flag & MNT_RDONLY) == 0)
+			ap->a_mode &= ~VWRITE;
+
 		error = VCALL(vp, VOFFSET(vop_access), ap);
 		if (error == 0) {
-			struct union_mount *um = MOUNTTOUNIONMOUNT(savedvp->v_mount);
+			struct union_mount *um;
+
+			um = MOUNTTOUNIONMOUNT(un->un_vnode->v_mount);
 
 			if (um->um_op == UNMNT_BELOW) {
 				ap->a_cred = um->um_cred;
@@ -723,17 +890,26 @@ union_access(ap)
 			}
 		}
 		VOP_UNLOCK(vp, 0, p);
-		if (error)
-			return (error);
 	}
-
-	return (error);
+	return(error);
 }
 
 /*
  * We handle getattr only to change the fsid and
  * track object sizes
+ *
+ * It's not clear whether VOP_GETATTR is to be
+ * called with the vnode locked or not.  stat() calls
+ * it with (vp) locked, and fstat calls it with
+ * (vp) unlocked. 
+ *
+ * Because of this we cannot use our normal locking functions
+ * if we do not intend to lock the main a_vp node.  At the moment
+ * we are running without any specific locking at all, but beware
+ * to any programmer that care must be taken if locking is added
+ * to this function.
  */
+
 static int
 union_getattr(ap)
 	struct vop_getattr_args /* {
@@ -745,12 +921,10 @@ union_getattr(ap)
 {
 	int error;
 	struct union_node *un = VTOUNION(ap->a_vp);
-	struct vnode *vp = un->un_uppervp;
-	struct proc *p = ap->a_p;
+	struct vnode *vp;
 	struct vattr *vap;
 	struct vattr va;
 
-
 	/*
 	 * Some programs walk the filesystem hierarchy by counting
 	 * links to directories to avoid stat'ing all the time.
@@ -762,22 +936,11 @@ union_getattr(ap)
 
 	vap = ap->a_vap;
 
-	vp = un->un_uppervp;
-	if (vp != NULLVP) {
-		/*
-		 * It's not clear whether VOP_GETATTR is to be
-		 * called with the vnode locked or not.  stat() calls
-		 * it with (vp) locked, and fstat calls it with
-		 * (vp) unlocked.
-		 * In the mean time, compensate here by checking
-		 * the union_node's lock flag.
-		 */
-		if (un->un_flags & UN_LOCKED)
-			FIXUP(un, p);
-
+	if ((vp = un->un_uppervp) != NULLVP) {
 		error = VOP_GETATTR(vp, vap, ap->a_cred, ap->a_p);
 		if (error)
 			return (error);
+		/* XXX isn't this dangerouso without a lock? */
 		union_newsize(ap->a_vp, vap->va_size, VNOVAL);
 	}
 
@@ -794,12 +957,12 @@ union_getattr(ap)
 		error = VOP_GETATTR(vp, vap, ap->a_cred, ap->a_p);
 		if (error)
 			return (error);
+		/* XXX isn't this dangerous without a lock? */
 		union_newsize(ap->a_vp, VNOVAL, vap->va_size);
 	}
 
 	if ((vap != ap->a_vap) && (vap->va_type == VDIR))
 		ap->a_vap->va_nlink += vap->va_nlink;
-
 	return (0);
 }
 
@@ -815,27 +978,28 @@ union_setattr(ap)
 	struct union_node *un = VTOUNION(ap->a_vp);
 	struct proc *p = ap->a_p;
 	struct vattr *vap = ap->a_vap;
+	struct vnode *uppervp;
 	int error;
 
 	/*
 	 * Disallow write attempts on filesystems mounted read-only.
 	 */
 	if ((ap->a_vp->v_mount->mnt_flag & MNT_RDONLY) &&
-		(vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
-		 vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
-		 vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL))
+	    (vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
+	     vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
+	     vap->va_mtime.tv_sec != VNOVAL || 
+	     vap->va_mode != (mode_t)VNOVAL)) {
 		return (EROFS);
+	}
 
 	/*
 	 * Handle case of truncating lower object to zero size,
 	 * by creating a zero length upper object.  This is to
 	 * handle the case of open with O_TRUNC and O_CREAT.
 	 */
-	if ((un->un_uppervp == NULLVP) &&
-	    /* assert(un->un_lowervp != NULLVP) */
-	    (un->un_lowervp->v_type == VREG)) {
+	if (un->un_uppervp == NULLVP && (un->un_lowervp->v_type == VREG)) {
 		error = union_copyup(un, (ap->a_vap->va_size != 0),
-						ap->a_cred, ap->a_p);
+			    ap->a_cred, ap->a_p);
 		if (error)
 			return (error);
 	}
@@ -844,19 +1008,45 @@ union_setattr(ap)
 	 * Try to set attributes in upper layer,
 	 * otherwise return read-only filesystem error.
 	 */
-	if (un->un_uppervp != NULLVP) {
-		FIXUP(un, p);
+	error = EROFS;
+	if ((uppervp = union_lock_upper(un, p)) != NULLVP) {
 		error = VOP_SETATTR(un->un_uppervp, ap->a_vap,
 					ap->a_cred, ap->a_p);
 		if ((error == 0) && (ap->a_vap->va_size != VNOVAL))
 			union_newsize(ap->a_vp, ap->a_vap->va_size, VNOVAL);
-	} else {
-		error = EROFS;
+		union_unlock_upper(uppervp, p);
 	}
-
 	return (error);
 }
 
+/*
+ *	union_getpages:
+ */
+
+static int
+union_getpages(struct vop_getpages_args *ap)
+{
+	int r;
+
+	r = vnode_pager_generic_getpages(ap->a_vp, ap->a_m, 
+		ap->a_count, ap->a_reqpage);
+	return(r);
+}
+
+/*
+ *	union_putpages:
+ */
+
+static int
+union_putpages(struct vop_putpages_args *ap)
+{
+	int r;
+
+	r = vnode_pager_generic_putpages(ap->a_vp, ap->a_m, ap->a_count,
+		ap->a_sync, ap->a_rtvals);
+	return(r);
+}
+
 static int
 union_read(ap)
 	struct vop_read_args /* {
@@ -866,18 +1056,19 @@ union_read(ap)
 		struct ucred *a_cred;
 	} */ *ap;
 {
-	int error;
+	struct union_node *un = VTOUNION(ap->a_vp);
 	struct proc *p = ap->a_uio->uio_procp;
-	struct vnode *vp = OTHERVP(ap->a_vp);
-	int dolock = (vp == LOWERVP(ap->a_vp));
+	struct vnode *uvp;
+	int error;
 
-	if (dolock)
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-	else
-		FIXUP(VTOUNION(ap->a_vp), p);
-	error = VOP_READ(vp, ap->a_uio, ap->a_ioflag, ap->a_cred);
-	if (dolock)
-		VOP_UNLOCK(vp, 0, p);
+	uvp = union_lock_other(un, p);
+	KASSERT(uvp != NULL, ("union_read: backing vnode missing!"));
+
+	if (ap->a_vp->v_flag & VOBJBUF)
+		union_vm_coherency(ap->a_vp, ap->a_uio, 0);
+
+	error = VOP_READ(uvp, ap->a_uio, ap->a_ioflag, ap->a_cred);
+	union_unlock_other(uvp, p);
 
 	/*
 	 * XXX
@@ -889,7 +1080,7 @@ union_read(ap)
 		struct union_node *un = VTOUNION(ap->a_vp);
 		off_t cur = ap->a_uio->uio_offset;
 
-		if (vp == un->un_uppervp) {
+		if (uvp == un->un_uppervp) {
 			if (cur > un->un_uppersz)
 				union_newsize(ap->a_vp, cur, VNOVAL);
 		} else {
@@ -897,7 +1088,6 @@ union_read(ap)
 				union_newsize(ap->a_vp, VNOVAL, cur);
 		}
 	}
-
 	return (error);
 }
 
@@ -910,17 +1100,36 @@ union_write(ap)
 		struct ucred *a_cred;
 	} */ *ap;
 {
-	int error;
-	struct vnode *vp;
 	struct union_node *un = VTOUNION(ap->a_vp);
 	struct proc *p = ap->a_uio->uio_procp;
+	struct vnode *uppervp;
+	int error;
 
-	vp = UPPERVP(ap->a_vp);
-	if (vp == NULLVP)
+	if ((uppervp = union_lock_upper(un, p)) == NULLVP)
 		panic("union: missing upper layer in write");
 
-	FIXUP(un, p);
-	error = VOP_WRITE(vp, ap->a_uio, ap->a_ioflag, ap->a_cred);
+	/*
+	 * Since our VM pages are associated with our vnode rather then
+	 * the real vnode, and since we do not run our reads and writes 
+	 * through our own VM cache, we have a VM/VFS coherency problem. 
+	 * We solve them by invalidating or flushing the associated VM
+	 * pages prior to allowing a normal read or write to occur.
+	 *
+	 * VM-backed writes (UIO_NOCOPY) have to be converted to normal
+	 * writes because we are not cache-coherent.  Normal writes need
+	 * to be made coherent with our VM-backing store, which we do by
+	 * first flushing any dirty VM pages associated with the write
+	 * range, and then destroying any clean VM pages associated with
+	 * the write range.
+	 */
+
+	if (ap->a_uio->uio_segflg == UIO_NOCOPY) {
+		ap->a_uio->uio_segflg = UIO_SYSSPACE;
+	} else if (ap->a_vp->v_flag & VOBJBUF) {
+		union_vm_coherency(ap->a_vp, ap->a_uio, 1);
+	}
+
+	error = VOP_WRITE(uppervp, ap->a_uio, ap->a_ioflag, ap->a_cred);
 
 	/*
 	 * the size of the underlying object may be changed by the
@@ -932,7 +1141,7 @@ union_write(ap)
 		if (cur > un->un_uppersz)
 			union_newsize(ap->a_vp, cur, VNOVAL);
 	}
-
+	union_unlock_upper(uppervp, p);
 	return (error);
 }
 
@@ -945,7 +1154,7 @@ union_lease(ap)
 		int a_flag;
 	} */ *ap;
 {
-	register struct vnode *ovp = OTHERVP(ap->a_vp);
+	struct vnode *ovp = OTHERVP(ap->a_vp);
 
 	ap->a_vp = ovp;
 	return (VCALL(ovp, VOFFSET(vop_lease), ap));
@@ -962,7 +1171,7 @@ union_ioctl(ap)
 		struct proc *a_p;
 	} */ *ap;
 {
-	register struct vnode *ovp = OTHERVP(ap->a_vp);
+	struct vnode *ovp = OTHERVP(ap->a_vp);
 
 	ap->a_vp = ovp;
 	return (VCALL(ovp, VOFFSET(vop_ioctl), ap));
@@ -977,7 +1186,7 @@ union_poll(ap)
 		struct proc *a_p;
 	} */ *ap;
 {
-	register struct vnode *ovp = OTHERVP(ap->a_vp);
+	struct vnode *ovp = OTHERVP(ap->a_vp);
 
 	ap->a_vp = ovp;
 	return (VCALL(ovp, VOFFSET(vop_poll), ap));
@@ -1010,7 +1219,7 @@ union_mmap(ap)
 		struct proc *a_p;
 	} */ *ap;
 {
-	register struct vnode *ovp = OTHERVP(ap->a_vp);
+	struct vnode *ovp = OTHERVP(ap->a_vp);
 
 	ap->a_vp = ovp;
 	return (VCALL(ovp, VOFFSET(vop_mmap), ap));
@@ -1027,35 +1236,24 @@ union_fsync(ap)
 {
 	int error = 0;
 	struct proc *p = ap->a_p;
-	struct vnode *targetvp = OTHERVP(ap->a_vp);
-	struct union_node *un;
-
-	if (targetvp != NULLVP) {
-		int dolock = (targetvp == LOWERVP(ap->a_vp));
-
-		un = VTOUNION(ap->a_vp);
-		if (dolock)
-			vn_lock(targetvp, LK_EXCLUSIVE | LK_RETRY, p);
-		else  {
-			un = VTOUNION(ap->a_vp);
-			if ((un->un_flags & UN_ULOCK) == 0 &&
-			    targetvp->v_data != NULL &&
-			    ((struct lock *)targetvp->v_data)->lk_lockholder
-			        == curproc->p_pid &&
-			    VOP_ISLOCKED(targetvp) != 0)
-				return 0;   /* XXX */
-
-			FIXUP(un, p);
-		}
+	struct vnode *targetvp;
+	struct union_node *un = VTOUNION(ap->a_vp);
 
+	if ((targetvp = union_lock_other(un, p)) != NULLVP) {
 		error = VOP_FSYNC(targetvp, ap->a_cred, ap->a_waitfor, p);
-		if (dolock)
-			VOP_UNLOCK(targetvp, 0, p);
+		union_unlock_other(targetvp, p);
 	}
 
 	return (error);
 }
 
+/*
+ *	union_remove:
+ *
+ *	Remove the specified cnp.  The dvp and vp are passed to us locked
+ *	and must remain locked on return.
+ */
+
 static int
 union_remove(ap)
 	struct vop_remove_args /* {
@@ -1068,42 +1266,40 @@ union_remove(ap)
 	struct union_node *un = VTOUNION(ap->a_vp);
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *uppervp;
+	struct vnode *upperdvp;
 	int error;
 
-	if (dun->un_uppervp == NULLVP)
+	if ((upperdvp = union_lock_upper(dun, p)) == NULLVP)
 		panic("union remove: null upper vnode");
 
-	if (un->un_uppervp != NULLVP) {
-		struct vnode *dvp = dun->un_uppervp;
-		struct vnode *vp = un->un_uppervp;
-
-		FIXUP(dun, p);
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
-		FIXUP(un, p);
-		un->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_vp, 0, p);
-
+	if ((uppervp = union_lock_upper(un, p)) != NULLVP) {
 		if (union_dowhiteout(un, cnp->cn_cred, p))
 			cnp->cn_flags |= DOWHITEOUT;
-		error = VOP_REMOVE(dvp, vp, cnp);
+		error = VOP_REMOVE(upperdvp, uppervp, cnp);
 #if 0
 		/* XXX */
 		if (!error)
 			union_removed_upper(un);
 #endif
-		dun->un_flags |= UN_ULOCK;
-		un->un_flags |= UN_ULOCK;
+		union_unlock_upper(uppervp, p);
 	} else {
-		FIXUP(dun, p);
 		error = union_mkwhiteout(
-			MOUNTTOUNIONMOUNT(UNIONTOV(dun)->v_mount),
-			dun->un_uppervp, ap->a_cnp, un->un_path);
+			    MOUNTTOUNIONMOUNT(ap->a_dvp->v_mount),
+			    upperdvp, ap->a_cnp, un->un_path);
 	}
-
+	union_unlock_upper(upperdvp, p);
 	return (error);
 }
 
+/*
+ *	union_link:
+ *
+ *	tdvp will be locked on entry, vp will not be locked on entry.
+ *	tdvp should remain locked on return and vp should remain unlocked
+ *	on return.
+ */
+
 static int
 union_link(ap)
 	struct vop_link_args /* {
@@ -1119,43 +1315,56 @@ union_link(ap)
 	struct vnode *tdvp;
 	int error = 0;
 
-
 	if (ap->a_tdvp->v_op != ap->a_vp->v_op) {
 		vp = ap->a_vp;
 	} else {
 		struct union_node *tun = VTOUNION(ap->a_vp);
+
 		if (tun->un_uppervp == NULLVP) {
 			vn_lock(ap->a_vp, LK_EXCLUSIVE | LK_RETRY, p);
+#if 0
 			if (dun->un_uppervp == tun->un_dirvp) {
-				dun->un_flags &= ~UN_ULOCK;
-				VOP_UNLOCK(dun->un_uppervp, 0, p);
+				if (dun->un_flags & UN_ULOCK) {
+					dun->un_flags &= ~UN_ULOCK;
+					VOP_UNLOCK(dun->un_uppervp, 0, p);
+				}
 			}
+#endif
 			error = union_copyup(tun, 1, cnp->cn_cred, p);
+#if 0
 			if (dun->un_uppervp == tun->un_dirvp) {
 				vn_lock(dun->un_uppervp,
-						LK_EXCLUSIVE | LK_RETRY, p);
+					    LK_EXCLUSIVE | LK_RETRY, p);
 				dun->un_flags |= UN_ULOCK;
 			}
+#endif
 			VOP_UNLOCK(ap->a_vp, 0, p);
 		}
 		vp = tun->un_uppervp;
 	}
 
-	tdvp = dun->un_uppervp;
-	if (tdvp == NULLVP)
-		error = EROFS;
-
 	if (error)
 		return (error);
 
-	FIXUP(dun, p);
-	dun->un_flags |= UN_KLOCK;
-	VOP_UNLOCK(ap->a_tdvp, 0, p);
+	/*
+	 * Make sure upper is locked, then unlock the union directory we were 
+	 * called with to avoid a deadlock while we are calling VOP_LINK on 
+	 * the upper (with tdvp locked and vp not locked).  Our ap->a_tdvp
+	 * is expected to be locked on return.
+	 */
 
-	error = VOP_LINK(tdvp, vp, cnp);
+	if ((tdvp = union_lock_upper(dun, p)) == NULLVP)
+		return (EROFS);
 
-	dun->un_flags |= UN_ULOCK;
+	VOP_UNLOCK(ap->a_tdvp, 0, p);		/* unlock calling node */
+	error = VOP_LINK(tdvp, vp, cnp);	/* call link on upper */
 
+	/*
+	 * We have to unlock tdvp prior to relocking our calling node in
+	 * order to avoid a deadlock.
+	 */
+	union_unlock_upper(tdvp, p);
+	vn_lock(ap->a_tdvp, LK_EXCLUSIVE | LK_RETRY, p);
 	return (error);
 }
 
@@ -1171,12 +1380,16 @@ union_rename(ap)
 	} */ *ap;
 {
 	int error;
-
 	struct vnode *fdvp = ap->a_fdvp;
 	struct vnode *fvp = ap->a_fvp;
 	struct vnode *tdvp = ap->a_tdvp;
 	struct vnode *tvp = ap->a_tvp;
 
+	/*
+	 * Figure out what fdvp to pass to our upper or lower vnode.  If we
+	 * replace the fdvp, release the original one and ref the new one.
+	 */
+
 	if (fdvp->v_op == union_vnodeop_p) {	/* always true */
 		struct union_node *un = VTOUNION(fdvp);
 		if (un->un_uppervp == NULLVP) {
@@ -1189,30 +1402,77 @@ union_rename(ap)
 			error = EXDEV;
 			goto bad;
 		}
-
 		fdvp = un->un_uppervp;
 		VREF(fdvp);
 		vrele(ap->a_fdvp);
 	}
 
+	/*
+	 * Figure out what fvp to pass to our upper or lower vnode.  If we
+	 * replace the fvp, release the original one and ref the new one.
+	 */
+
 	if (fvp->v_op == union_vnodeop_p) {	/* always true */
 		struct union_node *un = VTOUNION(fvp);
+#if 0
+		struct union_mount *um = MOUNTTOUNIONMOUNT(fvp->v_mount);
+#endif
+
 		if (un->un_uppervp == NULLVP) {
-			/* XXX: should do a copyup */
-			error = EXDEV;
-			goto bad;
+			switch(fvp->v_type) {
+			case VREG:
+				vn_lock(un->un_vnode, LK_EXCLUSIVE | LK_RETRY, ap->a_fcnp->cn_proc);
+				error = union_copyup(un, 1, ap->a_fcnp->cn_cred, ap->a_fcnp->cn_proc);
+				VOP_UNLOCK(un->un_vnode, 0, ap->a_fcnp->cn_proc);
+				if (error)
+					goto bad;
+				break;
+			case VDIR:
+				/*
+				 * XXX not yet.
+				 *
+				 * There is only one way to rename a directory
+				 * based in the lowervp, and that is to copy
+				 * the entire directory hierarchy.  Otherwise
+				 * it would not last across a reboot.
+				 */
+#if 0
+				vrele(fvp);
+				fvp = NULL;
+				vn_lock(fdvp, LK_EXCLUSIVE | LK_RETRY, ap->a_fcnp->cn_proc);
+				error = union_mkshadow(um, fdvp, 
+					    ap->a_fcnp, &un->un_uppervp);
+				VOP_UNLOCK(fdvp, 0, ap->a_fcnp->cn_proc);
+				if (un->un_uppervp)
+					VOP_UNLOCK(un->un_uppervp, 0, ap->a_fcnp->cn_proc);
+				if (error)
+					goto bad;
+				break;
+#endif
+			default:
+				error = EXDEV;
+				goto bad;
+			}
 		}
 
 		if (un->un_lowervp != NULLVP)
 			ap->a_fcnp->cn_flags |= DOWHITEOUT;
-
 		fvp = un->un_uppervp;
 		VREF(fvp);
 		vrele(ap->a_fvp);
 	}
 
+	/*
+	 * Figure out what tdvp (destination directory) to pass to the
+	 * lower level.  If we replace it with uppervp, we need to vput the 
+	 * old one.  The exclusive lock is transfered to what we will pass
+	 * down in the VOP_RENAME and we replace uppervp with a simple
+	 * reference.
+	 */
+
 	if (tdvp->v_op == union_vnodeop_p) {
 		struct union_node *un = VTOUNION(tdvp);
+
 		if (un->un_uppervp == NULLVP) {
 			/*
 			 * this should never happen in normal
@@ -1224,32 +1484,52 @@ union_rename(ap)
 			goto bad;
 		}
 
-		tdvp = un->un_uppervp;
-		VREF(tdvp);
-		un->un_flags |= UN_KLOCK;
+		/*
+		 * new tdvp is a lock and reference on uppervp, put away
+		 * the old tdvp.
+		 */
+		tdvp = union_lock_upper(un, ap->a_tcnp->cn_proc);
 		vput(ap->a_tdvp);
 	}
 
+	/*
+	 * Figure out what tvp (destination file) to pass to the
+	 * lower level.
+	 *
+	 * If the uppervp file does not exist put away the (wrong)
+	 * file and change tvp to NULL.
+	 */
+
 	if (tvp != NULLVP && tvp->v_op == union_vnodeop_p) {
 		struct union_node *un = VTOUNION(tvp);
 
-		tvp = un->un_uppervp;
-		if (tvp != NULLVP) {
-			VREF(tvp);
-			un->un_flags |= UN_KLOCK;
-		}
+		tvp = union_lock_upper(un, ap->a_tcnp->cn_proc);
 		vput(ap->a_tvp);
+		/* note: tvp may be NULL */
 	}
 
+	/*
+	 * VOP_RENAME releases/vputs prior to returning, so we have no
+	 * cleanup to do.
+	 */
+
 	return (VOP_RENAME(fdvp, fvp, ap->a_fcnp, tdvp, tvp, ap->a_tcnp));
 
+	/*
+	 * Error.  We still have to release / vput the various elements.
+	 */
+
 bad:
 	vrele(fdvp);
-	vrele(fvp);
+	if (fvp)
+		vrele(fvp);
 	vput(tdvp);
-	if (tvp != NULLVP)
-		vput(tvp);
-
+	if (tvp != NULLVP) {
+		if (tvp != tdvp)
+			vput(tvp);
+		else
+			vrele(tvp);
+	}
 	return (error);
 }
 
@@ -1263,34 +1543,26 @@ union_mkdir(ap)
 	} */ *ap;
 {
 	struct union_node *dun = VTOUNION(ap->a_dvp);
-	struct vnode *dvp = dun->un_uppervp;
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *upperdvp;
+	int error = EROFS;
 
-	if (dvp != NULLVP) {
+	if ((upperdvp = union_lock_upper(dun, p)) != NULLVP) {
 		struct vnode *vp;
-		int error;
-
-		FIXUP(dun, p);
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
-		error = VOP_MKDIR(dvp, &vp, cnp, ap->a_vap);
-		if (error) {
-			dun->un_flags |= UN_ULOCK;
-			return (error);
-		}
 
-		VOP_UNLOCK(dvp, 0, p);
-		error = union_allocvp(ap->a_vpp, ap->a_dvp->v_mount, ap->a_dvp,
-				NULLVP, cnp, vp, NULLVP, 1);
-		if (error)
-			vput(vp);
-		vn_lock(ap->a_dvp, LK_EXCLUSIVE| LK_RETRY, p);
+		error = VOP_MKDIR(upperdvp, &vp, cnp, ap->a_vap);
+		union_unlock_upper(upperdvp, p);
 
-		return (error);
+		if (error == 0) {
+			VOP_UNLOCK(vp, 0, p);
+			UDEBUG(("ALLOCVP-2 FROM %p REFS %d\n", vp, vp->v_usecount));
+			error = union_allocvp(ap->a_vpp, ap->a_dvp->v_mount,
+				ap->a_dvp, NULLVP, cnp, vp, NULLVP, 1);
+			UDEBUG(("ALLOCVP-2B FROM %p REFS %d\n", *ap->a_vpp, vp->v_usecount));
+		}
 	}
-
-	return (EROFS);
+	return (error);
 }
 
 static int
@@ -1305,42 +1577,34 @@ union_rmdir(ap)
 	struct union_node *un = VTOUNION(ap->a_vp);
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *upperdvp;
+	struct vnode *uppervp;
 	int error;
 
-	if (dun->un_uppervp == NULLVP)
+	if ((upperdvp = union_lock_upper(dun, p)) == NULLVP)
 		panic("union rmdir: null upper vnode");
 
-	if (un->un_uppervp != NULLVP) {
-		struct vnode *dvp = dun->un_uppervp;
-		struct vnode *vp = un->un_uppervp;
-
-		FIXUP(dun, p);
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
-		FIXUP(un, p);
-		un->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_vp, 0, p);
-
+	if ((uppervp = union_lock_upper(un, p)) != NULLVP) {
 		if (union_dowhiteout(un, cnp->cn_cred, p))
 			cnp->cn_flags |= DOWHITEOUT;
-		error = VOP_RMDIR(dvp, vp, ap->a_cnp);
-#if 0
-		/* XXX */
-		if (!error)
-			union_removed_upper(un);
-#endif
-		dun->un_flags |= UN_ULOCK;
-		un->un_flags |= UN_ULOCK;
+		error = VOP_RMDIR(upperdvp, uppervp, ap->a_cnp);
+		union_unlock_upper(uppervp, p);
 	} else {
-		FIXUP(dun, p);
 		error = union_mkwhiteout(
-			MOUNTTOUNIONMOUNT(UNIONTOV(dun)->v_mount),
-			dun->un_uppervp, ap->a_cnp, un->un_path);
+			    MOUNTTOUNIONMOUNT(ap->a_dvp->v_mount),
+			    dun->un_uppervp, ap->a_cnp, un->un_path);
 	}
-
+	union_unlock_upper(upperdvp, p);
 	return (error);
 }
 
+/*
+ *	union_symlink:
+ *
+ *	dvp is locked on entry and remains locked on return.  a_vpp is garbage
+ *	(unused).
+ */
+
 static int
 union_symlink(ap)
 	struct vop_symlink_args /* {
@@ -1352,24 +1616,20 @@ union_symlink(ap)
 	} */ *ap;
 {
 	struct union_node *dun = VTOUNION(ap->a_dvp);
-	struct vnode *dvp = dun->un_uppervp;
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *dvp;
+	int error = EROFS;
 
-	if (dvp != NULLVP) {
+	if ((dvp = union_lock_upper(dun, p)) != NULLVP) {
 		struct vnode *vp;
-		int error;
 
-		FIXUP(dun, p);
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
 		error = VOP_SYMLINK(dvp, &vp, cnp, ap->a_vap, ap->a_target);
-		dun->un_flags |= UN_ULOCK;
+		/* vp is garbage whether an error occurs or not */
 		*ap->a_vpp = NULLVP;
-		return (error);
+		union_unlock_upper(dvp, p);
 	}
-
-	return (EROFS);
+	return (error);
 }
 
 /*
@@ -1391,15 +1651,16 @@ union_readdir(ap)
 	} */ *ap;
 {
 	struct union_node *un = VTOUNION(ap->a_vp);
-	struct vnode *uvp = un->un_uppervp;
 	struct proc *p = ap->a_uio->uio_procp;
+	struct vnode *uvp;
+	int error = 0;
 
-	if (uvp == NULLVP)
-		return (0);
-
-	FIXUP(un, p);
-	ap->a_vp = uvp;
-	return (VCALL(uvp, VOFFSET(vop_readdir), ap));
+	if ((uvp = union_lock_upper(un, p)) != NULLVP) {
+		ap->a_vp = uvp;
+		error = VCALL(uvp, VOFFSET(vop_readdir), ap);
+		union_unlock_upper(uvp, p);
+	}
+	return(error);
 }
 
 static int
@@ -1411,23 +1672,28 @@ union_readlink(ap)
 	} */ *ap;
 {
 	int error;
+	struct union_node *un = VTOUNION(ap->a_vp);
 	struct uio *uio = ap->a_uio;
 	struct proc *p = uio->uio_procp;
-	struct vnode *vp = OTHERVP(ap->a_vp);
-	int dolock = (vp == LOWERVP(ap->a_vp));
+	struct vnode *vp;
+
+	vp = union_lock_other(un, p);
+	KASSERT(vp != NULL, ("union_readlink: backing vnode missing!"));
 
-	if (dolock)
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-	else
-		FIXUP(VTOUNION(ap->a_vp), p);
 	ap->a_vp = vp;
 	error = VCALL(vp, VOFFSET(vop_readlink), ap);
-	if (dolock)
-		VOP_UNLOCK(vp, 0, p);
+	union_unlock_other(vp, p);
 
 	return (error);
 }
 
+/*
+ *	union_abortop:
+ *
+ *	dvp is locked on entry and left locked on return
+ *
+ */
+
 static int
 union_abortop(ap)
 	struct vop_abortop_args /* {
@@ -1435,28 +1701,35 @@ union_abortop(ap)
 		struct componentname *a_cnp;
 	} */ *ap;
 {
-	int error;
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
-	struct vnode *vp = OTHERVP(ap->a_dvp);
 	struct union_node *un = VTOUNION(ap->a_dvp);
-	int islocked = un->un_flags & UN_LOCKED;
-	int dolock = (vp == LOWERVP(ap->a_dvp));
+	int islocked = VOP_ISLOCKED(ap->a_dvp);
+	struct vnode *vp;
+	int error;
 
 	if (islocked) {
-		if (dolock)
-			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-		else
-			FIXUP(VTOUNION(ap->a_dvp), p);
+		vp = union_lock_other(un, p);
+	} else {
+		vp = OTHERVP(ap->a_dvp);
 	}
+	KASSERT(vp != NULL, ("union_abortop: backing vnode missing!"));
+
 	ap->a_dvp = vp;
 	error = VCALL(vp, VOFFSET(vop_abortop), ap);
-	if (islocked && dolock)
-		VOP_UNLOCK(vp, 0, p);
+
+	if (islocked)
+		union_unlock_other(vp, p);
 
 	return (error);
 }
 
+/*
+ *	union_inactive:
+ *
+ *	Called with the vnode locked.  We are expected to unlock the vnode.
+ */
+
 static int
 union_inactive(ap)
 	struct vop_inactive_args /* {
@@ -1485,10 +1758,17 @@ union_inactive(ap)
 	if (un->un_dircache != 0) {
 		for (vpp = un->un_dircache; *vpp != NULLVP; vpp++)
 			vrele(*vpp);
-		free(un->un_dircache, M_TEMP);
+		free (un->un_dircache, M_TEMP);
 		un->un_dircache = 0;
 	}
 
+#if 0
+	if ((un->un_flags & UN_ULOCK) && un->un_uppervp) {
+		un->un_flags &= ~UN_ULOCK;
+		VOP_UNLOCK(un->un_uppervp, 0, p);
+	}
+#endif
+
 	VOP_UNLOCK(vp, 0, p);
 
 	if ((un->un_flags & UN_CACHED) == 0)
@@ -1503,7 +1783,6 @@ union_reclaim(ap)
 		struct vnode *a_vp;
 	} */ *ap;
 {
-
 	union_freevp(ap->a_vp);
 
 	return (0);
@@ -1513,75 +1792,47 @@ static int
 union_lock(ap)
 	struct vop_lock_args *ap;
 {
+#if 0
 	struct vnode *vp = ap->a_vp;
 	struct proc *p = ap->a_p;
 	int flags = ap->a_flags;
 	struct union_node *un;
+#endif
 	int error;
 
-	vop_nolock(ap);
-	/*
-	 * Need to do real lockmgr-style locking here.
-	 * in the mean time, draining won't work quite right,
-	 * which could lead to a few race conditions.
-	 * the following test was here, but is not quite right, we
-	 * still need to take the lock:
-	if ((flags & LK_TYPE_MASK) == LK_DRAIN)
-		return (0);
-	 */
-	flags &= ~LK_INTERLOCK;
-
-start:
+	error = vop_stdlock(ap);
+#if 0
 	un = VTOUNION(vp);
 
-	if (un->un_uppervp != NULLVP) {
-		if (((un->un_flags & UN_ULOCK) == 0) &&
-		    (vp->v_usecount != 0)) {
-			error = vn_lock(un->un_uppervp, flags, p);
-			if (error)
-				return (error);
-			un->un_flags |= UN_ULOCK;
-		}
-#ifdef DIAGNOSTIC
-		if (un->un_flags & UN_KLOCK) {
-			vprint("dangling upper lock", vp);
-			panic("union: dangling upper lock");
+	if (error == 0) {
+		/*
+		 * Lock the upper if it exists and this is an exclusive lock
+		 * request.
+		 */
+		if (un->un_uppervp != NULLVP && 
+		    (flags & LK_TYPE_MASK) == LK_EXCLUSIVE) {
+			if ((un->un_flags & UN_ULOCK) == 0 && vp->v_usecount) {
+				error = vn_lock(un->un_uppervp, flags, p);
+				if (error) {
+					struct vop_unlock_args uap = { 0 };
+					uap.a_vp = ap->a_vp;
+					uap.a_flags = ap->a_flags;
+					uap.a_p = ap->a_p;
+					vop_stdunlock(&uap);
+					return (error);
+				}
+				un->un_flags |= UN_ULOCK;
+			}
 		}
-#endif
 	}
-
-	if (un->un_flags & UN_LOCKED) {
-#ifdef DIAGNOSTIC
-		if (curproc && un->un_pid == curproc->p_pid &&
-			    un->un_pid > -1 && curproc->p_pid > -1)
-			panic("union: locking against myself");
-#endif
-		un->un_flags |= UN_WANT;
-		tsleep((caddr_t)&un->un_flags, PINOD, "unionlk2", 0);
-		goto start;
-	}
-
-#ifdef DIAGNOSTIC
-	if (curproc)
-		un->un_pid = curproc->p_pid;
-	else
-		un->un_pid = -1;
 #endif
-
-	un->un_flags |= UN_LOCKED;
-	return (0);
+	return (error);
 }
 
 /*
- * When operations want to vput() a union node yet retain a lock on
- * the upper vnode (say, to do some further operations like link(),
- * mkdir(), ...), they set UN_KLOCK on the union node, then call
- * vput() which calls VOP_UNLOCK() and comes here.  union_unlock()
- * unlocks the union node (leaving the upper vnode alone), clears the
- * KLOCK flag, and then returns to vput().  The caller then does whatever
- * is left to do with the upper vnode, and ensures that it gets unlocked.
+ *	union_unlock:
  *
- * If UN_KLOCK isn't set, then the upper vnode is unlocked here.
+ *	Unlock our union node.  This also unlocks uppervp.  
  */
 static int
 union_unlock(ap)
@@ -1592,36 +1843,38 @@ union_unlock(ap)
 	} */ *ap;
 {
 	struct union_node *un = VTOUNION(ap->a_vp);
-	struct proc *p = ap->a_p;
-
-#ifdef DIAGNOSTIC
-	if ((un->un_flags & UN_LOCKED) == 0)
-		panic("union: unlock unlocked node");
-	if (curproc && un->un_pid != curproc->p_pid &&
-			curproc->p_pid > -1 && un->un_pid > -1)
-		panic("union: unlocking other process's union node");
-#endif
+	int error;
 
-	un->un_flags &= ~UN_LOCKED;
+	KASSERT((un->un_uppervp == NULL || un->un_uppervp->v_usecount > 0), ("uppervp usecount is 0"));
 
-	if ((un->un_flags & (UN_ULOCK|UN_KLOCK)) == UN_ULOCK)
-		VOP_UNLOCK(un->un_uppervp, 0, p);
+	error = vop_stdunlock(ap);
+#if 0
 
-	un->un_flags &= ~(UN_ULOCK|UN_KLOCK);
+	/*
+	 * If no exclusive locks remain and we are holding an uppervp lock,
+	 * remove the uppervp lock.
+	 */
 
-	if (un->un_flags & UN_WANT) {
-		un->un_flags &= ~UN_WANT;
-		wakeup((caddr_t) &un->un_flags);
+	if ((un->un_flags & UN_ULOCK) && 
+	    lockstatus(&un->un_lock) != LK_EXCLUSIVE) {
+		un->un_flags &= ~UN_ULOCK;
+		VOP_UNLOCK(un->un_uppervp, LK_EXCLUSIVE, p);
 	}
-
-#ifdef DIAGNOSTIC
-	un->un_pid = 0;
 #endif
-	vop_nounlock(ap);
-
-	return (0);
+	return(error);
 }
 
+/*
+ *	union_bmap:
+ *
+ *	There isn't much we can do.  We cannot push through to the real vnode
+ *	to get to the underlying device because this will bypass data
+ *	cached by the real vnode.
+ *
+ *	For some reason we cannot return the 'real' vnode either, it seems
+ *	to blow up memory maps.
+ */
+
 static int
 union_bmap(ap)
 	struct vop_bmap_args /* {
@@ -1633,21 +1886,7 @@ union_bmap(ap)
 		int *a_runb;
 	} */ *ap;
 {
-	int error;
-	struct proc *p = curproc;		/* XXX */
-	struct vnode *vp = OTHERVP(ap->a_vp);
-	int dolock = (vp == LOWERVP(ap->a_vp));
-
-	if (dolock)
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-	else
-		FIXUP(VTOUNION(ap->a_vp), p);
-	ap->a_vp = vp;
-	error = VCALL(vp, VOFFSET(vop_bmap), ap);
-	if (dolock)
-		VOP_UNLOCK(vp, 0, p);
-
-	return (error);
+	return(EOPNOTSUPP);
 }
 
 static int
@@ -1669,16 +1908,6 @@ union_print(ap)
 }
 
 static int
-union_islocked(ap)
-	struct vop_islocked_args /* {
-		struct vnode *a_vp;
-	} */ *ap;
-{
-
-	return ((VTOUNION(ap->a_vp)->un_flags & UN_LOCKED) ? 1 : 0);
-}
-
-static int
 union_pathconf(ap)
 	struct vop_pathconf_args /* {
 		struct vnode *a_vp;
@@ -1688,17 +1917,15 @@ union_pathconf(ap)
 {
 	int error;
 	struct proc *p = curproc;		/* XXX */
-	struct vnode *vp = OTHERVP(ap->a_vp);
-	int dolock = (vp == LOWERVP(ap->a_vp));
+	struct union_node *un = VTOUNION(ap->a_vp);
+	struct vnode *vp;
+
+	vp = union_lock_other(un, p);
+	KASSERT(vp != NULL, ("union_pathconf: backing vnode missing!"));
 
-	if (dolock)
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-	else
-		FIXUP(VTOUNION(ap->a_vp), p);
 	ap->a_vp = vp;
 	error = VCALL(vp, VOFFSET(vop_pathconf), ap);
-	if (dolock)
-		VOP_UNLOCK(vp, 0, p);
+	union_unlock_other(vp, p);
 
 	return (error);
 }
@@ -1722,6 +1949,8 @@ union_advlock(ap)
 
 /*
  * XXX - vop_strategy must be hand coded because it has no
+ * YYY - and it is not coherent with anything
+ *
  * vnode in its arguments.
  * This goes away with a merged VM/buffer cache.
  */
@@ -1742,7 +1971,6 @@ union_strategy(ap)
 	    (othervp == LOWERVP(bp->b_vp)))
 		panic("union_strategy: writing to lowervp");
 #endif
-
 	return (VOP_STRATEGY(othervp, bp));
 }
 
@@ -1759,10 +1987,12 @@ static struct vnodeopv_entry_desc union_vnodeop_entries[] = {
 	{ &vop_close_desc,		(vop_t *) union_close },
 	{ &vop_create_desc,		(vop_t *) union_create },
 	{ &vop_fsync_desc,		(vop_t *) union_fsync },
+	{ &vop_getpages_desc,		(vop_t *) union_getpages },
+	{ &vop_putpages_desc,		(vop_t *) union_putpages },
 	{ &vop_getattr_desc,		(vop_t *) union_getattr },
 	{ &vop_inactive_desc,		(vop_t *) union_inactive },
 	{ &vop_ioctl_desc,		(vop_t *) union_ioctl },
-	{ &vop_islocked_desc,		(vop_t *) union_islocked },
+	{ &vop_islocked_desc,		(vop_t *) vop_stdislocked },
 	{ &vop_lease_desc,		(vop_t *) union_lease },
 	{ &vop_link_desc,		(vop_t *) union_link },
 	{ &vop_lock_desc,		(vop_t *) union_lock },
diff --git a/sys/miscfs/union/union.h b/sys/miscfs/union/union.h
index 1fc5f996cab0..02a897101472 100644
--- a/sys/miscfs/union/union.h
+++ b/sys/miscfs/union/union.h
@@ -49,8 +49,8 @@ struct union_args {
 #define UNMNT_OPMASK	0x0003
 
 struct union_mount {
-	struct vnode	*um_uppervp;
-	struct vnode	*um_lowervp;
+	struct vnode	*um_uppervp;	/* UN_ULOCK holds locking state */
+	struct vnode	*um_lowervp;	/* Left unlocked */
 	struct ucred	*um_cred;	/* Credentials of user calling mount */
 	int		um_cmode;	/* cmask from mount process */
 	int		um_op;		/* Operation mode */
@@ -58,6 +58,10 @@ struct union_mount {
 
 #ifdef KERNEL
 
+#ifndef DIAGNOSTIC
+#define DIAGNOSTIC
+#endif
+
 /*
  * DEFDIRMODE is the mode bits used to create a shadow directory.
  */
@@ -67,9 +71,14 @@ struct union_mount {
 #define UN_FILEMODE ((VRWMODE)|(VRWMODE>>3)|(VRWMODE>>6))
 
 /*
- * A cache of vnode references
+ * A cache of vnode references	(hangs off v_data)
+ *
+ * Placing un_lock as the first elements theoretically allows us to
+ * use the vop_stdlock functions.  However, we need to make sure of
+ * certain side effects so we will still punch in our own code.
  */
 struct union_node {
+	struct lock		un_lock;
 	LIST_ENTRY(union_node)	un_cache;	/* Hash chain */
 	struct vnode		*un_vnode;	/* Back pointer */
 	struct vnode	        *un_uppervp;	/* overlaying object */
@@ -79,6 +88,7 @@ struct union_node {
 	char			*un_path;	/* saved component name */
 	int			un_hash;	/* saved un_path hash value */
 	int			un_openl;	/* # of opens on lowervp */
+	int			un_exclcnt;	/* exclusive count */
 	unsigned int		un_flags;
 	struct vnode		**un_dircache;	/* cached union stack */
 	off_t			un_uppersz;	/* size of upper object */
@@ -88,14 +98,25 @@ struct union_node {
 #endif
 };
 
-#define UN_WANT		0x01
-#define UN_LOCKED	0x02
-#define UN_ULOCK	0x04		/* Upper node is locked */
-#define UN_KLOCK	0x08		/* Keep upper node locked on vput */
-#define UN_CACHED	0x10		/* In union cache */
+/*
+ * XXX UN_ULOCK -	indicates that the uppervp is locked
+ *
+ * UN_CACHED -	node is in the union cache
+ */
+
+/*#define UN_ULOCK	0x04*/	/* Upper node is locked */
+#define UN_CACHED	0x10	/* In union cache */
+
+/*
+ * Hash table locking flags
+ */
+
+#define UNVP_WANT	0x01
+#define UNVP_LOCKED	0x02
 
 extern int union_allocvp __P((struct vnode **, struct mount *,
-				struct vnode *, struct vnode *,
+				struct vnode *, 
+				struct vnode *, 
 				struct componentname *, struct vnode *,
 				struct vnode *, int));
 extern int union_freevp __P((struct vnode *));
@@ -113,6 +134,7 @@ extern int union_cn_close __P((struct vnode *, int, struct ucred *,
 extern void union_removed_upper __P((struct union_node *un));
 extern struct vnode *union_lowervp __P((struct vnode *));
 extern void union_newsize __P((struct vnode *, off_t, off_t));
+extern void union_vm_coherency __P((struct vnode *, struct uio *, int));
 
 extern int (*union_dircheckp) __P((struct proc *, struct vnode **,
 				 struct file *));
@@ -124,6 +146,11 @@ extern int (*union_dircheckp) __P((struct proc *, struct vnode **,
 #define	UPPERVP(vp) (VTOUNION(vp)->un_uppervp)
 #define OTHERVP(vp) (UPPERVP(vp) ? UPPERVP(vp) : LOWERVP(vp))
 
+#define UDEBUG(x)	if (uniondebug) printf x
+#define UDEBUG_ENABLED	1
+
 extern vop_t **union_vnodeop_p;
 extern struct vfsops union_vfsops;
+extern int uniondebug;
+
 #endif /* KERNEL */
diff --git a/sys/miscfs/union/union_subr.c b/sys/miscfs/union/union_subr.c
index ed09a65fbb4a..c03153c4894b 100644
--- a/sys/miscfs/union/union_subr.c
+++ b/sys/miscfs/union/union_subr.c
@@ -53,6 +53,7 @@
 #include <vm/vm.h>
 #include <vm/vm_extern.h>	/* for vnode_pager_setsize */
 #include <vm/vm_zone.h>
+#include <vm/vm_object.h>	/* for vm cache coherency */
 #include <miscfs/union/union.h>
 
 #include <sys/proc.h>
@@ -97,7 +98,7 @@ union_init()
 
 	for (i = 0; i < NHASH; i++)
 		LIST_INIT(&unhead[i]);
-	bzero((caddr_t) unvplock, sizeof(unvplock));
+	bzero((caddr_t)unvplock, sizeof(unvplock));
 	return (0);
 }
 
@@ -105,15 +106,12 @@ static int
 union_list_lock(ix)
 	int ix;
 {
-
-	if (unvplock[ix] & UN_LOCKED) {
-		unvplock[ix] |= UN_WANT;
+	if (unvplock[ix] & UNVP_LOCKED) {
+		unvplock[ix] |= UNVP_WANT;
 		(void) tsleep((caddr_t) &unvplock[ix], PINOD, "unllck", 0);
 		return (1);
 	}
-
-	unvplock[ix] |= UN_LOCKED;
-
+	unvplock[ix] |= UNVP_LOCKED;
 	return (0);
 }
 
@@ -121,15 +119,25 @@ static void
 union_list_unlock(ix)
 	int ix;
 {
+	unvplock[ix] &= ~UNVP_LOCKED;
 
-	unvplock[ix] &= ~UN_LOCKED;
-
-	if (unvplock[ix] & UN_WANT) {
-		unvplock[ix] &= ~UN_WANT;
+	if (unvplock[ix] & UNVP_WANT) {
+		unvplock[ix] &= ~UNVP_WANT;
 		wakeup((caddr_t) &unvplock[ix]);
 	}
 }
 
+/*
+ *	union_updatevp:
+ *
+ *	The uppervp, if not NULL, must be referenced and not locked by us
+ *	The lowervp, if not NULL, must be referenced.
+ *
+ *	if uppervp and lowervp match pointers already installed, nothing
+ *	happens. The passed vp's (when matching) are not adjusted.  This
+ *	routine may only be called by union_newupper() and union_newlower().
+ */
+
 static void
 union_updatevp(un, uppervp, lowervp)
 	struct union_node *un;
@@ -153,9 +161,10 @@ union_updatevp(un, uppervp, lowervp)
 		uhash = nhash;
 	}
 
-	if (lhash != uhash)
+	if (lhash != uhash) {
 		while (union_list_lock(lhash))
 			continue;
+	}
 
 	while (union_list_lock(uhash))
 		continue;
@@ -177,10 +186,6 @@ union_updatevp(un, uppervp, lowervp)
 				free(un->un_path, M_TEMP);
 				un->un_path = 0;
 			}
-			if (un->un_dirvp) {
-				vrele(un->un_dirvp);
-				un->un_dirvp = NULLVP;
-			}
 		}
 		un->un_lowervp = lowervp;
 		un->un_lowersz = VNOVAL;
@@ -189,7 +194,6 @@ union_updatevp(un, uppervp, lowervp)
 	if (un->un_uppervp != uppervp) {
 		if (un->un_uppervp)
 			vrele(un->un_uppervp);
-
 		un->un_uppervp = uppervp;
 		un->un_uppersz = VNOVAL;
 	}
@@ -202,21 +206,30 @@ union_updatevp(un, uppervp, lowervp)
 	union_list_unlock(nhash);
 }
 
+/*
+ * Set a new lowervp.  The passed lowervp must be referenced and will be
+ * stored in the vp in a referenced state. 
+ */
+
 static void
 union_newlower(un, lowervp)
 	struct union_node *un;
 	struct vnode *lowervp;
 {
-
 	union_updatevp(un, un->un_uppervp, lowervp);
 }
 
+/*
+ * Set a new uppervp.  The passed uppervp must be locked and will be 
+ * stored in the vp in a locked state.  The caller should not unlock
+ * uppervp.
+ */
+
 static void
 union_newupper(un, uppervp)
 	struct union_node *un;
 	struct vnode *uppervp;
 {
-
 	union_updatevp(un, uppervp, un->un_lowervp);
 }
 
@@ -253,27 +266,51 @@ union_newsize(vp, uppersz, lowersz)
 	}
 
 	if (sz != VNOVAL) {
-#ifdef DEBUG
-		printf("union: %s size now %ld\n",
-			uppersz != VNOVAL ? "upper" : "lower", (long) sz);
-#endif
+		UDEBUG(("union: %s size now %ld\n",
+			(uppersz != VNOVAL ? "upper" : "lower"), (long)sz));
 		vnode_pager_setsize(vp, sz);
 	}
 }
 
 /*
- * allocate a union_node/vnode pair.  the vnode is
- * referenced and locked.  the new vnode is returned
- * via (vpp).  (mp) is the mountpoint of the union filesystem,
- * (dvp) is the parent directory where the upper layer object
- * should exist (but doesn't) and (cnp) is the componentname
- * information which is partially copied to allow the upper
- * layer object to be created at a later time.  (uppervp)
- * and (lowervp) reference the upper and lower layer objects
- * being mapped.  either, but not both, can be nil.
- * if supplied, (uppervp) is locked.
- * the reference is either maintained in the new union_node
- * object which is allocated, or they are vrele'd.
+ *	union_allocvp:	allocate a union_node and associate it with a
+ *			parent union_node and one or two vnodes.
+ *
+ *	vpp	Holds the returned vnode locked and referenced if no 
+ *		error occurs.
+ *
+ *	mp	Holds the mount point.  mp may or may not be busied. 
+ *		allocvp makes no changes to mp.
+ *
+ *	dvp	Holds the parent union_node to the one we wish to create.
+ *		XXX may only be used to traverse an uncopied lowervp-based
+ *		tree?  XXX
+ *
+ *		dvp may or may not be locked.  allocvp makes no changes
+ *		to dvp.
+ *
+ *	upperdvp Holds the parent vnode to uppervp, generally used along
+ *		with path component information to create a shadow of
+ *		lowervp when uppervp does not exist.
+ *
+ *		upperdvp is referenced but unlocked on entry, and will be
+ *		dereferenced on return.
+ *
+ *	uppervp	Holds the new uppervp vnode to be stored in the 
+ *		union_node we are allocating.  uppervp is referenced but
+ *		not locked, and will be dereferenced on return.
+ *
+ *	lowervp	Holds the new lowervp vnode to be stored in the
+ *		union_node we are allocating.  uppervp is referenced but
+ *		not locked, and will be dereferenced on return.
+ * 
+ *	cnp	Holds path component information to be coupled with
+ *		lowervp and upperdvp to allow unionfs to create an uppervp
+ *		later on.  Only used if lowervp is valid.  The conents
+ *		of cnp is only valid for the duration of the call.
+ *
+ *	docache	Determine whether this node should be entered in the
+ *		cache or whether it should be destroyed as soon as possible.
  *
  * all union_nodes are maintained on a singly-linked
  * list.  new nodes are only allocated when they cannot
@@ -292,12 +329,13 @@ union_newsize(vp, uppersz, lowersz)
  * zero references to it and so it needs to removed from
  * the vnode free list.
  */
+
 int
-union_allocvp(vpp, mp, undvp, dvp, cnp, uppervp, lowervp, docache)
+union_allocvp(vpp, mp, dvp, upperdvp, cnp, uppervp, lowervp, docache)
 	struct vnode **vpp;
 	struct mount *mp;
-	struct vnode *undvp;		/* parent union vnode */
-	struct vnode *dvp;		/* may be null */
+	struct vnode *dvp;		/* parent union vnode */
+	struct vnode *upperdvp;		/* parent vnode of uppervp */
 	struct componentname *cnp;	/* may be null */
 	struct vnode *uppervp;		/* may be null */
 	struct vnode *lowervp;		/* may be null */
@@ -307,6 +345,7 @@ union_allocvp(vpp, mp, undvp, dvp, cnp, uppervp, lowervp, docache)
 	struct union_node *un = 0;
 	struct vnode *xlowervp = NULLVP;
 	struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
+	struct proc *p = (cnp) ? cnp->cn_proc : curproc;
 	int hash = 0;
 	int vflag;
 	int try;
@@ -382,65 +421,76 @@ loop:
 
 	if (un) {
 		/*
-		 * Obtain a lock on the union_node.
-		 * uppervp is locked, though un->un_uppervp
-		 * may not be.  this doesn't break the locking
-		 * hierarchy since in the case that un->un_uppervp
-		 * is not yet locked it will be vrele'd and replaced
-		 * with uppervp.
+		 * Obtain a lock on the union_node.  Everything is unlocked
+		 * except for dvp, so check that case.  If they match, our
+		 * new un is already locked.  Otherwise we have to lock our
+		 * new un.
+		 *
+		 * A potential deadlock situation occurs when we are holding
+		 * one lock while trying to get another.  We must follow 
+		 * strict ordering rules to avoid it.  We try to locate dvp
+		 * by scanning up from un_vnode, since the most likely 
+		 * scenario is un being under dvp.
 		 */
 
-		if ((dvp != NULLVP) && (uppervp == dvp)) {
+		if (dvp && un->un_vnode != dvp) {
+			struct vnode *scan = un->un_vnode;
+
+			do {
+				scan = VTOUNION(scan)->un_pvp;
+			} while (scan && scan->v_tag == VT_UNION && scan != dvp);
+			if (scan != dvp) {
+				/*
+				 * our new un is above dvp (we never saw dvp
+				 * while moving up the tree).
+				 */
+				VREF(dvp);
+				VOP_UNLOCK(dvp, 0, p);
+				error = vn_lock(un->un_vnode, LK_EXCLUSIVE, p);
+				vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
+				vrele(dvp);
+			} else {
+				/*
+				 * our new un is under dvp
+				 */
+				error = vn_lock(un->un_vnode, LK_EXCLUSIVE, p);
+			}
+		} else if (dvp == NULLVP) {
 			/*
-			 * Access ``.'', so (un) will already
-			 * be locked.  Since this process has
-			 * the lock on (uppervp) no other
-			 * process can hold the lock on (un).
+			 * dvp is NULL, we need to lock un.
 			 */
-#ifdef DIAGNOSTIC
-			if ((un->un_flags & UN_LOCKED) == 0)
-				panic("union: . not locked");
-			else if (curproc && un->un_pid != curproc->p_pid &&
-				    un->un_pid > -1 && curproc->p_pid > -1)
-				panic("union: allocvp not lock owner");
-#endif
+			error = vn_lock(un->un_vnode, LK_EXCLUSIVE, p);
 		} else {
-			if (un->un_flags & UN_LOCKED) {
-				vrele(UNIONTOV(un));
-				un->un_flags |= UN_WANT;
-				(void) tsleep((caddr_t) &un->un_flags, PINOD, "unalvp", 0);
-				goto loop;
-			}
-			un->un_flags |= UN_LOCKED;
-
-#ifdef DIAGNOSTIC
-			if (curproc)
-				un->un_pid = curproc->p_pid;
-			else
-				un->un_pid = -1;
-#endif
+			/*
+			 * dvp == un->un_vnode, we are already locked.
+			 */
+			error = 0;
 		}
 
-		/*
-		 * At this point, the union_node is locked,
-		 * un->un_uppervp may not be locked, and uppervp
-		 * is locked or nil.
-		 */
+		if (error)
+			goto loop;
 
 		/*
-		 * Save information about the upper layer.
+		 * At this point, the union_node is locked and referenced.
+		 *
+		 * uppervp is locked and referenced or NULL, lowervp is
+		 * referenced or NULL.
 		 */
+		UDEBUG(("Modify existing un %p vn %p upper %p(refs %d) -> %p(refs %d)\n",
+			un, un->un_vnode, un->un_uppervp, 
+			(un->un_uppervp ? un->un_uppervp->v_usecount : -99),
+			uppervp,
+			(uppervp ? uppervp->v_usecount : -99)
+		));
+
 		if (uppervp != un->un_uppervp) {
+			KASSERT(uppervp == NULL || uppervp->v_usecount > 0, ("union_allocvp: too few refs %d (at least 1 required) on uppervp", uppervp->v_usecount));
 			union_newupper(un, uppervp);
 		} else if (uppervp) {
+			KASSERT(uppervp->v_usecount > 1, ("union_allocvp: too few refs %d (at least 2 required) on uppervp", uppervp->v_usecount));
 			vrele(uppervp);
 		}
 
-		if (un->un_uppervp) {
-			un->un_flags |= UN_ULOCK;
-			un->un_flags &= ~UN_KLOCK;
-		}
-
 		/*
 		 * Save information about the lower layer.
 		 * This needs to keep track of pathname
@@ -456,12 +506,22 @@ loop:
 				bcopy(cnp->cn_nameptr, un->un_path,
 						cnp->cn_namelen);
 				un->un_path[cnp->cn_namelen] = '\0';
-				VREF(dvp);
-				un->un_dirvp = dvp;
 			}
 		} else if (lowervp) {
 			vrele(lowervp);
 		}
+
+		/*
+		 * and upperdvp
+		 */
+		if (upperdvp != un->un_dirvp) {
+			if (un->un_dirvp)
+				vrele(un->un_dirvp);
+			un->un_dirvp = upperdvp;
+		} else if (upperdvp) {
+			vrele(upperdvp);
+		}
+
 		*vpp = UNIONTOV(un);
 		return (0);
 	}
@@ -477,17 +537,22 @@ loop:
 			goto loop;
 	}
 
+	/*
+	 * Create new node rather then replace old node
+	 */
+
 	error = getnewvnode(VT_UNION, mp, union_vnodeop_p, vpp);
 	if (error) {
-		if (uppervp) {
-			if (dvp == uppervp)
-				vrele(uppervp);
-			else
-				vput(uppervp);
-		}
+		/*
+		 * If an error occurs clear out vnodes.
+		 */
 		if (lowervp)
 			vrele(lowervp);
-
+		if (uppervp) 
+			vrele(uppervp);
+		if (upperdvp)
+			vrele(upperdvp);
+		*vpp = NULL;
 		goto out;
 	}
 
@@ -499,37 +564,34 @@ loop:
 		(*vpp)->v_type = uppervp->v_type;
 	else
 		(*vpp)->v_type = lowervp->v_type;
+
 	un = VTOUNION(*vpp);
+	bzero(un, sizeof(*un));
+
+	lockinit(&un->un_lock, PVFS, "unlock", 0, 0);
+	vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY, p);
+
 	un->un_vnode = *vpp;
 	un->un_uppervp = uppervp;
 	un->un_uppersz = VNOVAL;
 	un->un_lowervp = lowervp;
 	un->un_lowersz = VNOVAL;
-	un->un_pvp = undvp;
-	if (undvp != NULLVP)
-		VREF(undvp);
+	un->un_dirvp = upperdvp;
+	un->un_pvp = dvp;		/* only parent dir in new allocation */
+	if (dvp != NULLVP)
+		VREF(dvp);
 	un->un_dircache = 0;
 	un->un_openl = 0;
-	un->un_flags = UN_LOCKED;
-	if (un->un_uppervp)
-		un->un_flags |= UN_ULOCK;
-#ifdef DIAGNOSTIC
-	if (curproc)
-		un->un_pid = curproc->p_pid;
-	else
-		un->un_pid = -1;
-#endif
+
 	if (cnp && (lowervp != NULLVP)) {
 		un->un_hash = cnp->cn_hash;
 		un->un_path = malloc(cnp->cn_namelen+1, M_TEMP, M_WAITOK);
 		bcopy(cnp->cn_nameptr, un->un_path, cnp->cn_namelen);
 		un->un_path[cnp->cn_namelen] = '\0';
-		VREF(dvp);
-		un->un_dirvp = dvp;
 	} else {
 		un->un_hash = 0;
 		un->un_path = 0;
-		un->un_dirvp = 0;
+		un->un_dirvp = NULL;
 	}
 
 	if (docache) {
@@ -537,10 +599,10 @@ loop:
 		un->un_flags |= UN_CACHED;
 	}
 
+out:
 	if (xlowervp)
 		vrele(xlowervp);
 
-out:
 	if (docache)
 		union_list_unlock(hash);
 
@@ -558,16 +620,26 @@ union_freevp(vp)
 		LIST_REMOVE(un, un_cache);
 	}
 
-	if (un->un_pvp != NULLVP)
+	if (un->un_pvp != NULLVP) {
 		vrele(un->un_pvp);
-	if (un->un_uppervp != NULLVP)
+		un->un_pvp = NULL;
+	}
+	if (un->un_uppervp != NULLVP) {
 		vrele(un->un_uppervp);
-	if (un->un_lowervp != NULLVP)
+		un->un_uppervp = NULL;
+	}
+	if (un->un_lowervp != NULLVP) {
 		vrele(un->un_lowervp);
-	if (un->un_dirvp != NULLVP)
+		un->un_lowervp = NULL;
+	}
+	if (un->un_dirvp != NULLVP) {
 		vrele(un->un_dirvp);
-	if (un->un_path)
+		un->un_dirvp = NULL;
+	}
+	if (un->un_path) {
 		free(un->un_path, M_TEMP);
+		un->un_path = NULL;
+	}
 
 	FREE(vp->v_data, M_TEMP);
 	vp->v_data = 0;
@@ -579,6 +651,9 @@ union_freevp(vp)
  * copyfile.  copy the vnode (fvp) to the vnode (tvp)
  * using a sequence of reads and writes.  both (fvp)
  * and (tvp) are locked on entry and exit.
+ *
+ * fvp and tvp are both exclusive locked on call, but their refcount's
+ * haven't been bumped at all.
  */
 static int
 union_copyfile(fvp, tvp, cred, p)
@@ -600,48 +675,62 @@ union_copyfile(fvp, tvp, cred, p)
 	 * give up at the first sign of trouble.
 	 */
 
+	bzero(&uio, sizeof(uio));
+
 	uio.uio_procp = p;
 	uio.uio_segflg = UIO_SYSSPACE;
 	uio.uio_offset = 0;
 
-	VOP_UNLOCK(fvp, 0, p);				/* XXX */
 	VOP_LEASE(fvp, p, cred, LEASE_READ);
-	vn_lock(fvp, LK_EXCLUSIVE | LK_RETRY, p);	/* XXX */
-	VOP_UNLOCK(tvp, 0, p);				/* XXX */
 	VOP_LEASE(tvp, p, cred, LEASE_WRITE);
-	vn_lock(tvp, LK_EXCLUSIVE | LK_RETRY, p);	/* XXX */
 
 	buf = malloc(MAXBSIZE, M_TEMP, M_WAITOK);
 
 	/* ugly loop follows... */
 	do {
 		off_t offset = uio.uio_offset;
+		int count;
+		int bufoffset;
 
+		/*
+		 * Setup for big read
+		 */
 		uio.uio_iov = &iov;
 		uio.uio_iovcnt = 1;
 		iov.iov_base = buf;
 		iov.iov_len = MAXBSIZE;
 		uio.uio_resid = iov.iov_len;
 		uio.uio_rw = UIO_READ;
-		error = VOP_READ(fvp, &uio, 0, cred);
 
-		if (error == 0) {
+		if ((error = VOP_READ(fvp, &uio, 0, cred)) != 0)
+			break;
+
+		/*
+		 * Get bytes read, handle read eof case and setup for
+		 * write loop
+		 */
+		if ((count = MAXBSIZE - uio.uio_resid) == 0)
+			break;
+		bufoffset = 0;
+
+		/*
+		 * Write until an error occurs or our buffer has been
+		 * exhausted, then update the offset for the next read.
+		 */
+		while (bufoffset < count) {
 			uio.uio_iov = &iov;
 			uio.uio_iovcnt = 1;
-			iov.iov_base = buf;
-			iov.iov_len = MAXBSIZE - uio.uio_resid;
-			uio.uio_offset = offset;
+			iov.iov_base = buf + bufoffset;
+			iov.iov_len = count - bufoffset;
+			uio.uio_offset = offset + bufoffset;
 			uio.uio_rw = UIO_WRITE;
 			uio.uio_resid = iov.iov_len;
 
-			if (uio.uio_resid == 0)
+			if ((error = VOP_WRITE(tvp, &uio, 0, cred)) != 0)
 				break;
-
-			do {
-				error = VOP_WRITE(tvp, &uio, 0, cred);
-			} while ((uio.uio_resid > 0) && (error == 0));
+			bufoffset += (count - bufoffset) - uio.uio_resid;
 		}
-
+		uio.uio_offset = offset + bufoffset;
 	} while (error == 0);
 
 	free(buf, M_TEMP);
@@ -649,9 +738,10 @@ union_copyfile(fvp, tvp, cred, p)
 }
 
 /*
- * (un) is assumed to be locked on entry and remains
- * locked on exit.
+ *
+ * un's vnode is assumed to be locked on entry and remains locked on exit.
  */
+
 int
 union_copyup(un, docopy, cred, p)
 	struct union_node *un;
@@ -676,12 +766,9 @@ union_copyup(un, docopy, cred, p)
 	if (error)
 		return (error);
 
-	/* at this point, uppervp is locked */
-	union_newupper(un, uvp);
-	un->un_flags |= UN_ULOCK;
-
 	lvp = un->un_lowervp;
 
+	KASSERT(uvp->v_usecount > 0, ("copy: uvp refcount 0: %d", uvp->v_usecount));
 	if (docopy) {
 		/*
 		 * XX - should not ignore errors
@@ -689,23 +776,22 @@ union_copyup(un, docopy, cred, p)
 		 */
 		vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, p);
 		error = VOP_OPEN(lvp, FREAD, cred, p);
+		if (error == 0 && vn_canvmio(lvp) == TRUE)
+			error = vfs_object_create(lvp, p, cred);
 		if (error == 0) {
 			error = union_copyfile(lvp, uvp, cred, p);
 			VOP_UNLOCK(lvp, 0, p);
 			(void) VOP_CLOSE(lvp, FREAD, cred, p);
 		}
-#ifdef DEBUG
 		if (error == 0)
-			uprintf("union: copied up %s\n", un->un_path);
-#endif
+			UDEBUG(("union: copied up %s\n", un->un_path));
 
 	}
-	un->un_flags &= ~UN_ULOCK;
 	VOP_UNLOCK(uvp, 0, p);
+	union_newupper(un, uvp);
+	KASSERT(uvp->v_usecount > 0, ("copy: uvp refcount 0: %d", uvp->v_usecount));
 	union_vn_close(uvp, FWRITE, cred, p);
-	vn_lock(uvp, LK_EXCLUSIVE | LK_RETRY, p);
-	un->un_flags |= UN_ULOCK;
-
+	KASSERT(uvp->v_usecount > 0, ("copy: uvp refcount 0: %d", uvp->v_usecount));
 	/*
 	 * Subsequent IOs will go to the top layer, so
 	 * call close on the lower vnode and open on the
@@ -721,6 +807,8 @@ union_copyup(un, docopy, cred, p)
 			(void) VOP_CLOSE(lvp, FREAD, cred, p);
 			(void) VOP_OPEN(uvp, FREAD, cred, p);
 		}
+		if (vn_canvmio(uvp) == TRUE)
+			error = vfs_object_create(uvp, p, cred);
 		un->un_openl = 0;
 	}
 
@@ -728,6 +816,17 @@ union_copyup(un, docopy, cred, p)
 
 }
 
+/*
+ *	union_relookup:
+ *
+ *	dvp should be locked on entry and will be locked on return.  No
+ *	net change in the ref count will occur.
+ *
+ *	If an error is returned, *vpp will be invalid, otherwise it
+ *	will hold a locked, referenced vnode.  If *vpp == dvp then
+ *	remember that only one exclusive lock is held.
+ */
+
 static int
 union_relookup(um, dvp, vpp, cnp, cn, path, pathlen)
 	struct union_mount *um;
@@ -757,7 +856,7 @@ union_relookup(um, dvp, vpp, cnp, cn, path, pathlen)
 	cn->cn_pnbuf[cn->cn_namelen] = '\0';
 
 	cn->cn_nameiop = CREATE;
-	cn->cn_flags = (LOCKPARENT|HASBUF|SAVENAME|SAVESTART|ISLASTCN);
+	cn->cn_flags = (LOCKPARENT|LOCKLEAF|HASBUF|SAVENAME|ISLASTCN);
 	cn->cn_proc = cnp->cn_proc;
 	if (um->um_op == UNMNT_ABOVE)
 		cn->cn_cred = cnp->cn_cred;
@@ -768,15 +867,30 @@ union_relookup(um, dvp, vpp, cnp, cn, path, pathlen)
 	cn->cn_consume = cnp->cn_consume;
 
 	VREF(dvp);
-	error = relookup(dvp, vpp, cn);
-	if (!error)
-		vrele(dvp);
-	else {
+	VOP_UNLOCK(dvp, 0, cnp->cn_proc);
+
+	/*
+	 * Pass dvp unlocked and referenced on call to relookup().
+	 *
+	 * If an error occurs, dvp will be returned unlocked and dereferenced.
+	 */
+
+	if ((error = relookup(dvp, vpp, cn)) != 0) {
 		zfree(namei_zone, cn->cn_pnbuf);
 		cn->cn_pnbuf = NULL;
+		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, cnp->cn_proc);
+		return(error);
 	}
 
-	return (error);
+	/*
+	 * If no error occurs, dvp will be returned locked with the reference
+	 * left as before, and vpp will be returned referenced and locked.
+	 *
+	 * We want to return with dvp as it was passed to us, so we get
+	 * rid of our reference.
+	 */
+	vrele(dvp);
+	return (0);
 }
 
 /*
@@ -785,11 +899,11 @@ union_relookup(um, dvp, vpp, cnp, cn, path, pathlen)
  *
  * (um) points to the union mount structure for access to the
  * the mounting process's credentials.
- * (dvp) is the directory in which to create the shadow directory.
- * it is unlocked on entry and exit.
+ * (dvp) is the directory in which to create the shadow directory,
+ * it is locked (but not ref'd) on entry and return.
  * (cnp) is the componentname to be created.
  * (vpp) is the returned newly created shadow directory, which
- * is returned locked.
+ * is returned locked and ref'd
  */
 int
 union_mkshadow(um, dvp, cnp, vpp)
@@ -810,8 +924,10 @@ union_mkshadow(um, dvp, cnp, vpp)
 
 	if (*vpp) {
 		VOP_ABORTOP(dvp, &cn);
-		VOP_UNLOCK(dvp, 0, p);
-		vrele(*vpp);
+		if (dvp == *vpp)
+			vrele(*vpp);
+		else
+			vput(*vpp);
 		*vpp = NULLVP;
 		return (EEXIST);
 	}
@@ -832,7 +948,7 @@ union_mkshadow(um, dvp, cnp, vpp)
 	VOP_LEASE(dvp, p, cn.cn_cred, LEASE_WRITE);
 
 	error = VOP_MKDIR(dvp, vpp, &cn, &va);
-	vput(dvp);
+	/*vput(dvp);*/
 	return (error);
 }
 
@@ -842,7 +958,7 @@ union_mkshadow(um, dvp, cnp, vpp)
  * (um) points to the union mount structure for access to the
  * the mounting process's credentials.
  * (dvp) is the directory in which to create the whiteout.
- * it is locked on entry and exit.
+ * it is locked on entry and return.
  * (cnp) is the componentname to be created.
  */
 int
@@ -857,17 +973,16 @@ union_mkwhiteout(um, dvp, cnp, path)
 	struct vnode *wvp;
 	struct componentname cn;
 
-	VOP_UNLOCK(dvp, 0, p);
 	error = union_relookup(um, dvp, &wvp, cnp, &cn, path, strlen(path));
-	if (error) {
-		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
+	if (error)
 		return (error);
-	}
 
 	if (wvp) {
 		VOP_ABORTOP(dvp, &cn);
-		vrele(dvp);
-		vrele(wvp);
+		if (wvp == dvp)
+			vrele(wvp);
+		else
+			vput(wvp);
 		return (EEXIST);
 	}
 
@@ -877,9 +992,6 @@ union_mkwhiteout(um, dvp, cnp, path)
 	error = VOP_WHITEOUT(dvp, &cn, CREATE);
 	if (error)
 		VOP_ABORTOP(dvp, &cn);
-
-	vrele(dvp);
-
 	return (error);
 }
 
@@ -890,6 +1002,12 @@ union_mkwhiteout(um, dvp, cnp, path)
  * the problem with calling namei is that a) it locks too many
  * things, and b) it doesn't start at the "right" directory,
  * whereas relookup is told where to start.
+ *
+ * On entry, the vnode associated with un is locked.  It remains locked
+ * on return.
+ *
+ * If no error occurs, *vpp contains a locked referenced vnode for your
+ * use.  If an error occurs *vpp iis undefined.
  */
 static int
 union_vn_create(vpp, un, p)
@@ -921,26 +1039,34 @@ union_vn_create(vpp, un, p)
 	cn.cn_pnbuf = zalloc(namei_zone);
 	bcopy(un->un_path, cn.cn_pnbuf, cn.cn_namelen+1);
 	cn.cn_nameiop = CREATE;
-	cn.cn_flags = (LOCKPARENT|HASBUF|SAVENAME|SAVESTART|ISLASTCN);
+	cn.cn_flags = (LOCKPARENT|LOCKLEAF|HASBUF|SAVENAME|ISLASTCN);
 	cn.cn_proc = p;
 	cn.cn_cred = p->p_ucred;
 	cn.cn_nameptr = cn.cn_pnbuf;
 	cn.cn_hash = un->un_hash;
 	cn.cn_consume = 0;
 
+	/*
+	 * Pass dvp unlocked and referenced on call to relookup().
+	 *
+	 * If an error occurs, dvp will be returned unlocked and dereferenced.
+	 */
 	VREF(un->un_dirvp);
 	error = relookup(un->un_dirvp, &vp, &cn);
 	if (error)
 		return (error);
-	vrele(un->un_dirvp);
 
+	/*
+	 * If no error occurs, dvp will be returned locked with the reference
+	 * left as before, and vpp will be returned referenced and locked.
+	 */
 	if (vp) {
+		vput(un->un_dirvp);
 		VOP_ABORTOP(un->un_dirvp, &cn);
-		if (un->un_dirvp == vp)
-			vrele(un->un_dirvp);
+		if (vp == un->un_dirvp)
+			vrele(vp);
 		else
-			vput(un->un_dirvp);
-		vrele(vp);
+			vput(vp);
 		return (EEXIST);
 	}
 
@@ -964,11 +1090,12 @@ union_vn_create(vpp, un, p)
 		return (error);
 
 	error = VOP_OPEN(vp, fmode, cred, p);
+	if (error == 0 && vn_canvmio(vp) == TRUE)
+		error = vfs_object_create(vp, p, cred);
 	if (error) {
 		vput(vp);
 		return (error);
 	}
-
 	vp->v_writecount++;
 	*vpp = vp;
 	return (0);
@@ -987,6 +1114,14 @@ union_vn_close(vp, fmode, cred, p)
 	return (VOP_CLOSE(vp, fmode, cred, p));
 }
 
+#if 0
+
+/*
+ *	union_removed_upper:
+ *
+ *	called with union_node unlocked. XXX
+ */
+
 void
 union_removed_upper(un)
 	struct union_node *un;
@@ -999,9 +1134,7 @@ union_removed_upper(un)
 	 * union node will have neither uppervp nor lowervp.  We remove
 	 * the union node from cache, so that it will not be referrenced.
 	 */
-#if 0
 	union_newupper(un, NULLVP);
-#endif
 	if (un->un_dircache != 0) {
 		for (vpp = un->un_dircache; *vpp != NULLVP; vpp++)
 			vrele(*vpp);
@@ -1013,28 +1146,8 @@ union_removed_upper(un)
 		un->un_flags &= ~UN_CACHED;
 		LIST_REMOVE(un, un_cache);
 	}
-
-	if (un->un_flags & UN_ULOCK) {
-		un->un_flags &= ~UN_ULOCK;
-		VOP_UNLOCK(un->un_uppervp, 0, p);
-	}
 }
 
-#if 0
-struct vnode *
-union_lowervp(vp)
-	struct vnode *vp;
-{
-	struct union_node *un = VTOUNION(vp);
-
-	if ((un->un_lowervp != NULLVP) &&
-	    (vp->v_type == un->un_lowervp->v_type)) {
-		if (vget(un->un_lowervp, 0) == 0)
-			return (un->un_lowervp);
-	}
-
-	return (NULLVP);
-}
 #endif
 
 /*
@@ -1104,13 +1217,12 @@ union_dircache(vp, p)
 
 	nvp = NULLVP;
 
-	if (dircache == 0) {
+	if (dircache == NULL) {
 		cnt = 0;
 		union_dircache_r(vp, 0, &cnt);
 		cnt++;
-		dircache = (struct vnode **)
-				malloc(cnt * sizeof(struct vnode *),
-					M_TEMP, M_WAITOK);
+		dircache = malloc(cnt * sizeof(struct vnode *),
+				M_TEMP, M_WAITOK);
 		vpp = dircache;
 		union_dircache_r(vp, &vpp, &cnt);
 		*vpp = NULLVP;
@@ -1126,9 +1238,11 @@ union_dircache(vp, p)
 	if (*vpp == NULLVP)
 		goto out;
 
-	vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY, p);
+	/*vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY, p);*/
+	UDEBUG(("ALLOCVP-3 %p ref %d\n", *vpp, (*vpp ? (*vpp)->v_usecount : -99)));
 	VREF(*vpp);
-	error = union_allocvp(&nvp, vp->v_mount, NULLVP, NULLVP, 0, *vpp, NULLVP, 0);
+	error = union_allocvp(&nvp, vp->v_mount, NULLVP, NULLVP, NULL, *vpp, NULLVP, 0);
+	UDEBUG(("ALLOCVP-3B %p ref %d\n", nvp, (*vpp ? (*vpp)->v_usecount : -99)));
 	if (error)
 		goto out;
 
@@ -1142,6 +1256,40 @@ out:
 }
 
 /*
+ * Guarentee coherency with the VM cache by invalidating any clean VM pages
+ * associated with this write and updating any dirty VM pages.  Since our
+ * vnode is locked, other processes will not be able to read the pages in
+ * again until after our write completes.
+ *
+ * We also have to be coherent with reads, by flushing any pending dirty
+ * pages prior to issuing the read.
+ *
+ * XXX this is somewhat of a hack at the moment.  To support this properly
+ * we would have to be able to run VOP_READ and VOP_WRITE through the VM
+ * cache.  Then we wouldn't need to worry about coherency.
+ */
+
+void 
+union_vm_coherency(struct vnode *vp, struct uio *uio, int cleanfls)
+{
+	vm_object_t object;
+	vm_pindex_t pstart;
+	vm_pindex_t pend;
+	int pgoff;
+
+	if ((object = vp->v_object) == NULL)
+	    return;
+
+	pgoff = uio->uio_offset & PAGE_MASK;
+	pstart = uio->uio_offset / PAGE_SIZE;
+	pend = pstart + (uio->uio_resid + pgoff + PAGE_MASK) / PAGE_SIZE;
+
+	vm_object_page_clean(object, pstart, pend, OBJPC_SYNC);
+	if (cleanfls)
+		vm_object_page_remove(object, pstart, pend, TRUE);
+}
+
+/*
  * Module glue to remove #ifdef UNION from vfs_syscalls.c
  */
 static int
@@ -1169,6 +1317,8 @@ union_dircheck(struct proc *p, struct vnode **vp, struct file *fp)
 
 		if (lvp != NULLVP) {
 			error = VOP_OPEN(lvp, FREAD, fp->f_cred, p);
+			if (error == 0 && vn_canvmio(lvp) == TRUE)
+				error = vfs_object_create(lvp, p, fp->f_cred);
 			if (error) {
 				vput(lvp);
 				return (error);
@@ -1201,9 +1351,11 @@ union_modevent(module_t mod, int type, void *data)
 	}
 	return 0;
 }
+
 static moduledata_t union_mod = {
 	"union_dircheck",
 	union_modevent,
 	NULL
 };
+
 DECLARE_MODULE(union_dircheck, union_mod, SI_SUB_VFS, SI_ORDER_ANY);
diff --git a/sys/miscfs/union/union_vfsops.c b/sys/miscfs/union/union_vfsops.c
index af828ac64a8c..1a53f88bcc7b 100644
--- a/sys/miscfs/union/union_vfsops.c
+++ b/sys/miscfs/union/union_vfsops.c
@@ -85,9 +85,7 @@ union_mount(mp, path, data, ndp, p)
 	int len;
 	u_int size;
 
-#ifdef DEBUG
-	printf("union_mount(mp = %p)\n", (void *)mp);
-#endif
+	UDEBUG(("union_mount(mp = %p)\n", (void *)mp));
 
 	/*
 	 * Disable clustered write, otherwise system becomes unstable.
@@ -114,24 +112,35 @@ union_mount(mp, path, data, ndp, p)
 	if (error)
 		goto bad;
 
+	/*
+	 * Obtain lower vnode.  Vnode is stored in mp->mnt_vnodecovered.
+	 * We need to reference it but not lock it.
+	 */
+
 	lowerrootvp = mp->mnt_vnodecovered;
 	VREF(lowerrootvp);
 
+#if 0
 	/*
 	 * Unlock lower node to avoid deadlock.
 	 */
 	if (lowerrootvp->v_op == union_vnodeop_p)
 		VOP_UNLOCK(lowerrootvp, 0, p);
+#endif
 
 	/*
-	 * Find upper node.
+	 * Obtain upper vnode by calling namei() on the path.  The
+	 * upperrootvp will be turned referenced but not locked.
 	 */
 	NDINIT(ndp, LOOKUP, FOLLOW|WANTPARENT,
 	       UIO_USERSPACE, args.target, p);
 
 	error = namei(ndp);
+
+#if 0
 	if (lowerrootvp->v_op == union_vnodeop_p)
 		vn_lock(lowerrootvp, LK_EXCLUSIVE | LK_RETRY, p);
+#endif
 	if (error)
 		goto bad;
 
@@ -139,8 +148,11 @@ union_mount(mp, path, data, ndp, p)
 	vrele(ndp->ni_dvp);
 	ndp->ni_dvp = NULL;
 
+	UDEBUG(("mount_root UPPERVP %p locked = %d\n", upperrootvp, VOP_ISLOCKED(upperrootvp)));
+
 	/*
 	 * Check multi union mount to avoid `lock myself again' panic.
+	 * Also require that it be a directory.
 	 */
 	if (upperrootvp == VTOUNION(lowerrootvp)->un_uppervp) {
 #ifdef DIAGNOSTIC
@@ -155,35 +167,43 @@ union_mount(mp, path, data, ndp, p)
 		goto bad;
 	}
 
-	um = (struct union_mount *) malloc(sizeof(struct union_mount),
-				M_UNIONFSMNT, M_WAITOK);	/* XXX */
-
 	/*
-	 * Keep a held reference to the target vnodes.
-	 * They are vrele'd in union_unmount.
-	 *
-	 * Depending on the _BELOW flag, the filesystems are
-	 * viewed in a different order.  In effect, this is the
-	 * same as providing a mount under option to the mount syscall.
+	 * Allocate our union_mount structure and populate the fields.
+	 * The vnode references are stored in the union_mount as held,
+	 * unlocked references.  Depending on the _BELOW flag, the
+	 * filesystems are viewed in a different order.  In effect this
+	 * is the same as providing a mount-under option to the mount
+	 * syscall.
 	 */
 
+	um = (struct union_mount *) malloc(sizeof(struct union_mount),
+				M_UNIONFSMNT, M_WAITOK);
+
+	bzero(um, sizeof(struct union_mount));
+
 	um->um_op = args.mntflags & UNMNT_OPMASK;
+
 	switch (um->um_op) {
 	case UNMNT_ABOVE:
 		um->um_lowervp = lowerrootvp;
 		um->um_uppervp = upperrootvp;
+		upperrootvp = NULL;
+		lowerrootvp = NULL;
 		break;
 
 	case UNMNT_BELOW:
 		um->um_lowervp = upperrootvp;
 		um->um_uppervp = lowerrootvp;
+		upperrootvp = NULL;
+		lowerrootvp = NULL;
 		break;
 
 	case UNMNT_REPLACE:
 		vrele(lowerrootvp);
-		lowerrootvp = NULLVP;
+		lowerrootvp = NULL;
 		um->um_uppervp = upperrootvp;
 		um->um_lowervp = lowerrootvp;
+		upperrootvp = NULL;
 		break;
 
 	default:
@@ -196,7 +216,7 @@ union_mount(mp, path, data, ndp, p)
 	 * supports whiteout operations
 	 */
 	if ((mp->mnt_flag & MNT_RDONLY) == 0) {
-		error = VOP_WHITEOUT(um->um_uppervp, (struct componentname *) 0, LOOKUP);
+		error = VOP_WHITEOUT(um->um_uppervp, NULL, LOOKUP);
 		if (error)
 			goto bad;
 	}
@@ -258,15 +278,19 @@ union_mount(mp, path, data, ndp, p)
 
 	(void)union_statfs(mp, &mp->mnt_stat, p);
 
-#ifdef DEBUG
-	printf("union_mount: from %s, on %s\n",
-		mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
-#endif
+	UDEBUG(("union_mount: from %s, on %s\n",
+		mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname));
 	return (0);
 
 bad:
-	if (um)
+	if (um) {
+		if (um->um_uppervp)
+			vrele(um->um_uppervp);
+		if (um->um_lowervp)
+			vrele(um->um_lowervp);
+		/* XXX other fields */
 		free(um, M_UNIONFSMNT);
+	}
 	if (cred)
 		crfree(cred);
 	if (upperrootvp)
@@ -291,9 +315,7 @@ union_unmount(mp, mntflags, p)
 	int freeing;
 	int flags = 0;
 
-#ifdef DEBUG
-	printf("union_unmount(mp = %p)\n", (void *)mp);
-#endif
+	UDEBUG(("union_unmount(mp = %p)\n", (void *)mp));
 
 	if (mntflags & MNT_FORCE)
 		flags |= FORCECLOSE;
@@ -365,55 +387,25 @@ union_root(mp, vpp)
 	struct mount *mp;
 	struct vnode **vpp;
 {
-	struct proc *p = curproc;	/* XXX */
 	struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
 	int error;
-	int loselock;
-	int lockadj = 0;
-
-	if (um->um_lowervp && um->um_op != UNMNT_BELOW &&
-		VOP_ISLOCKED(um->um_lowervp)) {
-		VREF(um->um_lowervp);
-		VOP_UNLOCK(um->um_lowervp, 0, p);
-		lockadj = 1;
-	}
 
 	/*
-	 * Return locked reference to root.
+	 * Supply an unlocked reference to um_uppervp and to um_lowervp.  It
+	 * is possible for um_uppervp to be locked without the associated
+	 * root union_node being locked.  We let union_allocvp() deal with
+	 * it.
 	 */
+	UDEBUG(("union_root UPPERVP %p locked = %d\n", um->um_uppervp, VOP_ISLOCKED(um->um_uppervp)));
+
 	VREF(um->um_uppervp);
-	if ((um->um_op == UNMNT_BELOW) &&
-	    VOP_ISLOCKED(um->um_uppervp)) {
-		loselock = 1;
-	} else {
-		vn_lock(um->um_uppervp, LK_EXCLUSIVE | LK_RETRY, p);
-		loselock = 0;
-	}
 	if (um->um_lowervp)
 		VREF(um->um_lowervp);
-	error = union_allocvp(vpp, mp,
-			      (struct vnode *) 0,
-			      (struct vnode *) 0,
-			      (struct componentname *) 0,
-			      um->um_uppervp,
-			      um->um_lowervp,
-			      1);
 
-	if (error) {
-		if (loselock)
-			vrele(um->um_uppervp);
-		else
-			vput(um->um_uppervp);
-		if (um->um_lowervp)
-			vrele(um->um_lowervp);
-	} else {
-		if (loselock)
-			VTOUNION(*vpp)->un_flags &= ~UN_ULOCK;
-	}
-	if (lockadj) {
-		vn_lock(um->um_lowervp, LK_EXCLUSIVE | LK_RETRY, p);
-		vrele(um->um_lowervp);
-	}
+	error = union_allocvp(vpp, mp, NULLVP, NULLVP, NULL, 
+		    um->um_uppervp, um->um_lowervp, 1);
+	UDEBUG(("error %d\n", error));
+	UDEBUG(("union_root2 UPPERVP %p locked = %d\n", um->um_uppervp, VOP_ISLOCKED(um->um_uppervp)));
 
 	return (error);
 }
@@ -429,10 +421,8 @@ union_statfs(mp, sbp, p)
 	struct statfs mstat;
 	int lbsize;
 
-#ifdef DEBUG
-	printf("union_statfs(mp = %p, lvp = %p, uvp = %p)\n",
-	    (void *)mp, (void *)um->um_lowervp, (void *)um->um_uppervp);
-#endif
+	UDEBUG(("union_statfs(mp = %p, lvp = %p, uvp = %p)\n",
+	    (void *)mp, (void *)um->um_lowervp, (void *)um->um_uppervp));
 
 	bzero(&mstat, sizeof(mstat));
 
diff --git a/sys/miscfs/union/union_vnops.c b/sys/miscfs/union/union_vnops.c
index 145f8ca6f0ad..128e59ebaa21 100644
--- a/sys/miscfs/union/union_vnops.c
+++ b/sys/miscfs/union/union_vnops.c
@@ -50,13 +50,25 @@
 #include <sys/malloc.h>
 #include <sys/buf.h>
 #include <sys/lock.h>
+#include <sys/sysctl.h>
 #include <miscfs/union/union.h>
 
-#define FIXUP(un, p) { \
-	if (((un)->un_flags & UN_ULOCK) == 0) { \
-		union_fixup(un, p); \
-	} \
-}
+#include <vm/vm.h>
+#include <vm/vnode_pager.h>
+
+#include <vm/vm_prot.h>
+#include <vm/vm_page.h>
+#include <vm/vm_object.h>
+#include <vm/vm_pager.h>
+#include <vm/vm_extern.h>
+
+int uniondebug = 0;
+
+#if UDEBUG_ENABLED
+SYSCTL_INT(_vfs, OID_AUTO, uniondebug, CTLFLAG_RW, &uniondebug, 0, "");
+#else
+SYSCTL_INT(_vfs, OID_AUTO, uniondebug, CTLFLAG_RD, &uniondebug, 0, "");
+#endif
 
 static int	union_abortop __P((struct vop_abortop_args *ap));
 static int	union_access __P((struct vop_access_args *ap));
@@ -64,17 +76,15 @@ static int	union_advlock __P((struct vop_advlock_args *ap));
 static int	union_bmap __P((struct vop_bmap_args *ap));
 static int	union_close __P((struct vop_close_args *ap));
 static int	union_create __P((struct vop_create_args *ap));
-static void	union_fixup __P((struct union_node *un, struct proc *p));
 static int	union_fsync __P((struct vop_fsync_args *ap));
 static int	union_getattr __P((struct vop_getattr_args *ap));
 static int	union_inactive __P((struct vop_inactive_args *ap));
 static int	union_ioctl __P((struct vop_ioctl_args *ap));
-static int	union_islocked __P((struct vop_islocked_args *ap));
 static int	union_lease __P((struct vop_lease_args *ap));
 static int	union_link __P((struct vop_link_args *ap));
 static int	union_lock __P((struct vop_lock_args *ap));
 static int	union_lookup __P((struct vop_lookup_args *ap));
-static int	union_lookup1 __P((struct vnode *udvp, struct vnode **dvpp,
+static int	union_lookup1 __P((struct vnode *udvp, struct vnode **dvp,
 				   struct vnode **vpp,
 				   struct componentname *cnp));
 static int	union_mkdir __P((struct vop_mkdir_args *ap));
@@ -94,36 +104,89 @@ static int	union_rmdir __P((struct vop_rmdir_args *ap));
 static int	union_poll __P((struct vop_poll_args *ap));
 static int	union_setattr __P((struct vop_setattr_args *ap));
 static int	union_strategy __P((struct vop_strategy_args *ap));
+static int	union_getpages __P((struct vop_getpages_args *ap));
+static int	union_putpages __P((struct vop_putpages_args *ap));
 static int	union_symlink __P((struct vop_symlink_args *ap));
 static int	union_unlock __P((struct vop_unlock_args *ap));
 static int	union_whiteout __P((struct vop_whiteout_args *ap));
 static int	union_write __P((struct vop_read_args *ap));
 
-static void
-union_fixup(un, p)
-	struct union_node *un;
-	struct proc *p;
+static __inline
+struct vnode *
+union_lock_upper(struct union_node *un, struct proc *p)
 {
+	struct vnode *uppervp;
+
+	if ((uppervp = un->un_uppervp) != NULL) {
+		VREF(uppervp);
+		vn_lock(uppervp, LK_EXCLUSIVE | LK_CANRECURSE | LK_RETRY, p);
+	}
+	KASSERT((uppervp == NULL || uppervp->v_usecount > 0), ("uppervp usecount is 0"));
+	return(uppervp);
+}
+
+static __inline
+void
+union_unlock_upper(struct vnode *uppervp, struct proc *p)
+{
+	vput(uppervp);
+}
+
+static __inline
+struct vnode *
+union_lock_other(struct union_node *un, struct proc *p)
+{
+	struct vnode *vp;
 
-	vn_lock(un->un_uppervp, LK_EXCLUSIVE | LK_RETRY, p);
-	un->un_flags |= UN_ULOCK;
+	if (un->un_uppervp != NULL) {
+		vp = union_lock_upper(un, p);
+	} else if ((vp = un->un_lowervp) != NULL) {
+		VREF(vp);
+		vn_lock(vp, LK_EXCLUSIVE | LK_CANRECURSE | LK_RETRY, p);
+	}
+	return(vp);
+}
+
+static __inline
+void
+union_unlock_other(struct vnode *vp, struct proc *p)
+{
+	vput(vp);
 }
 
+/*
+ *	union_lookup:
+ *
+ *	udvp	must be exclusively locked on call and will remain 
+ *		exclusively locked on return.  This is the mount point 
+ *		for out filesystem.
+ *
+ *	dvp	Our base directory, locked and referenced.
+ *		The passed dvp will be dereferenced and unlocked on return
+ *		and a new dvp will be returned which is locked and 
+ *		referenced in the same variable.
+ *
+ *	vpp	is filled in with the result if no error occured,
+ *		locked and ref'd.
+ *
+ *		If an error is returned, *vpp is set to NULLVP.  If no
+ *		error occurs, *vpp is returned with a reference and an
+ *		exclusive lock.
+ */
+
 static int
-union_lookup1(udvp, dvpp, vpp, cnp)
+union_lookup1(udvp, pdvp, vpp, cnp)
 	struct vnode *udvp;
-	struct vnode **dvpp;
+	struct vnode **pdvp;
 	struct vnode **vpp;
 	struct componentname *cnp;
 {
 	int error;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *dvp = *pdvp;
 	struct vnode *tdvp;
-	struct vnode *dvp;
 	struct mount *mp;
 
-	dvp = *dvpp;
-
 	/*
 	 * If stepping up the directory tree, check for going
 	 * back across the mount point, in which case do what
@@ -139,49 +202,79 @@ union_lookup1(udvp, dvpp, vpp, cnp)
 			 * filesystems.
 			 */
 			tdvp = dvp;
-			*dvpp = dvp = dvp->v_mount->mnt_vnodecovered;
-			vput(tdvp);
+			dvp = dvp->v_mount->mnt_vnodecovered;
 			VREF(dvp);
+			vput(tdvp);
 			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
 		}
 	}
 
+	/*
+	 * Set return dvp to be the upperdvp 'parent directory.
+	 */
+	*pdvp = dvp;
+
+	/*
+	 * If the VOP_LOOKUP call generates an error, tdvp is invalid and no
+	 * changes will have been made to dvp, so we are set to return.
+	 */
+
         error = VOP_LOOKUP(dvp, &tdvp, cnp);
-	if (error)
+	if (error) {
+		UDEBUG(("dvp %p error %d flags %lx\n", dvp, error, cnp->cn_flags));
+		*vpp = NULL;
 		return (error);
+	}
 
 	/*
 	 * The parent directory will have been unlocked, unless lookup
-	 * found the last component.  In which case, re-lock the node
-	 * here to allow it to be unlocked again (phew) in union_lookup.
+	 * found the last component or if dvp == tdvp (tdvp must be locked).
+	 *
+	 * We want our dvp to remain locked and ref'd.  We also want tdvp
+	 * to remain locked and ref'd.
 	 */
-	if (dvp != tdvp && !(cnp->cn_flags & ISLASTCN))
-		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
+	UDEBUG(("parentdir %p result %p flag %lx\n", dvp, tdvp, cnp->cn_flags));
 
-	dvp = tdvp;
+	if (dvp != tdvp && (cnp->cn_flags & ISLASTCN) == 0)
+		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
 
 	/*
 	 * Lastly check if the current node is a mount point in
 	 * which case walk up the mount hierarchy making sure not to
 	 * bump into the root of the mount tree (ie. dvp != udvp).
+	 *
+	 * We use dvp as a temporary variable here, it is no longer related
+	 * to the dvp above.  However, we have to ensure that both *pdvp and
+	 * tdvp are locked on return.
 	 */
-	while (dvp != udvp && (dvp->v_type == VDIR) &&
-	       (mp = dvp->v_mountedhere)) {
+
+	dvp = tdvp;
+	while (
+	    dvp != udvp && 
+	    (dvp->v_type == VDIR) &&
+	    (mp = dvp->v_mountedhere)
+	) {
+		int relock_pdvp = 0;
 
 		if (vfs_busy(mp, 0, 0, p))
 			continue;
 
-		error = VFS_ROOT(mp, &tdvp);
+		if (dvp == *pdvp)
+			relock_pdvp = 1;
+		vput(dvp);
+		dvp = NULL;
+		error = VFS_ROOT(mp, &dvp);
+
 		vfs_unbusy(mp, p);
+
+		if (relock_pdvp)
+			vn_lock(*pdvp, LK_EXCLUSIVE | LK_RETRY, p);
+
 		if (error) {
-			vput(dvp);
+			*vpp = NULL;
 			return (error);
 		}
-
-		vput(dvp);
-		dvp = tdvp;
 	}
-
 	*vpp = dvp;
 	return (0);
 }
@@ -199,8 +292,8 @@ union_lookup(ap)
 	int uerror, lerror;
 	struct vnode *uppervp, *lowervp;
 	struct vnode *upperdvp, *lowerdvp;
-	struct vnode *dvp = ap->a_dvp;
-	struct union_node *dun = VTOUNION(dvp);
+	struct vnode *dvp = ap->a_dvp;		/* starting dir */
+	struct union_node *dun = VTOUNION(dvp);	/* associated union node */
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
 	int lockparent = cnp->cn_flags & LOCKPARENT;
@@ -209,44 +302,38 @@ union_lookup(ap)
 	int iswhiteout;
 	struct vattr va;
 
+	*ap->a_vpp = NULLVP;
 
 	/*
 	 * Disallow write attemps to the filesystem mounted read-only.
 	 */
-	if ((cnp->cn_flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
-		(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
+	if ((cnp->cn_flags & ISLASTCN) && 
+	    (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
+	    (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
 		return (EROFS);
-
-#ifdef notyet
-	if (cnp->cn_namelen == 3 &&
-			cnp->cn_nameptr[2] == '.' &&
-			cnp->cn_nameptr[1] == '.' &&
-			cnp->cn_nameptr[0] == '.') {
-		dvp = *ap->a_vpp = LOWERVP(ap->a_dvp);
-		if (dvp == NULLVP)
-			return (ENOENT);
-		VREF(dvp);
-		vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
-		if (!lockparent || !(cnp->cn_flags & ISLASTCN))
-			VOP_UNLOCK(ap->a_dvp, 0, p);
-		return (0);
 	}
-#endif
 
+	/*
+	 * For any lookup's we do, always return with the parent locked
+	 */
 	cnp->cn_flags |= LOCKPARENT;
 
-	upperdvp = dun->un_uppervp;
 	lowerdvp = dun->un_lowervp;
 	uppervp = NULLVP;
 	lowervp = NULLVP;
 	iswhiteout = 0;
 
-	if (cnp->cn_flags & ISDOTDOT) {
-		if (upperdvp != NULL)
-			VREF(upperdvp);
-		if (lowerdvp != NULL)
-			VREF(lowerdvp);
-	}
+	uerror = ENOENT;
+	lerror = ENOENT;
+
+	/*
+	 * Get a private lock on uppervp and a reference, effectively 
+	 * taking it out of the union_node's control.
+	 *
+	 * We must lock upperdvp while holding our lock on dvp
+	 * to avoid a deadlock.
+	 */
+	upperdvp = union_lock_upper(dun, p);
 
 	/*
 	 * do the lookup in the upper level.
@@ -255,62 +342,64 @@ union_lookup(ap)
 	 * on and just return that vnode.
 	 */
 	if (upperdvp != NULLVP) {
-		FIXUP(dun, p);
 		/*
-		 * If we're doing `..' in the underlying filesystem,
-		 * we must drop our lock on the union node before
-		 * going up the tree in the lower file system--if we block
-		 * on the lowervp lock, and that's held by someone else
-		 * coming down the tree and who's waiting for our lock,
-		 * we would be hosed.
+		 * We do not have to worry about the DOTDOT case, we've
+		 * already unlocked dvp.
 		 */
-		if (cnp->cn_flags & ISDOTDOT) {
-			/* retain lock on underlying VP: */
-			dun->un_flags |= UN_KLOCK;
-			VOP_UNLOCK(dvp, 0, p);
-		}
-		uerror = union_lookup1(um->um_uppervp, &upperdvp,
-					&uppervp, cnp);
+		UDEBUG(("A %p\n", upperdvp));
+
+		/*
+		 * Do the lookup.   We must supply a locked and referenced
+		 * upperdvp to the function and will get a new locked and
+		 * referenced upperdvp back with the old having been 
+		 * dereferenced.
+		 *
+		 * If an error is returned, uppervp will be NULLVP.  If no
+		 * error occurs, uppervp will be the locked and referenced
+		 * return vnode or possibly NULL, depending on what is being
+		 * requested.  It is possible that the returned uppervp
+		 * will be the same as upperdvp.
+		 */
+		uerror = union_lookup1(um->um_uppervp, &upperdvp, &uppervp, cnp);
+		UDEBUG((
+		    "uerror %d upperdvp %p %d/%d, uppervp %p ref=%d/lck=%d\n",
+		    uerror,
+		    upperdvp,
+		    upperdvp->v_usecount,
+		    VOP_ISLOCKED(upperdvp),
+		    uppervp,
+		    (uppervp ? uppervp->v_usecount : -99),
+		    (uppervp ? VOP_ISLOCKED(uppervp) : -99)
+		));
+
 		/*
 		 * Disallow write attemps to the filesystem mounted read-only.
 		 */
 		if (uerror == EJUSTRETURN && (cnp->cn_flags & ISLASTCN) &&
-			(dvp->v_mount->mnt_flag & MNT_RDONLY) &&
-			(cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME)) {
-			if (!lockparent)
-				cnp->cn_flags &= ~LOCKPARENT;
-			return (EROFS);
-		}
-			
-		if (cnp->cn_flags & ISDOTDOT) {
-			if (dun->un_uppervp == upperdvp) {
-				/*
-				 * We got the underlying bugger back locked...
-				 * now take back the union node lock.  Since we
-				 * hold the uppervp lock, we can diddle union
-				 * locking flags at will. :)
-				 */
-				dun->un_flags |= UN_ULOCK;
-			}
-			/*
-			 * If upperdvp got swapped out, it means we did
-			 * some mount point magic, and we do not have
-			 * dun->un_uppervp locked currently--so we get it
-			 * locked here (don't set the UN_ULOCK flag).
-			 */
-			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, p);
+		    (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
+		    (cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME)) {
+			error = EROFS;
+			goto out;
 		}
 
-		/*if (uppervp == upperdvp)
-			dun->un_flags |= UN_KLOCK;*/
+		/*
+		 * Special case.  If cn_consume != 0 skip out.  The result
+		 * of the lookup is transfered to our return variable.  If
+		 * an error occured we have to throw away the results.
+		 */
 
 		if (cnp->cn_consume != 0) {
-			*ap->a_vpp = uppervp;
-			if (!lockparent)
-				cnp->cn_flags &= ~LOCKPARENT;
-			error = uerror;
+			if ((error = uerror) == 0) {
+				*ap->a_vpp = uppervp;
+				uppervp = NULL;
+			}
 			goto out;
 		}
+
+		/*
+		 * Calculate whiteout, fall through
+		 */
+
 		if (uerror == ENOENT || uerror == EJUSTRETURN) {
 			if (cnp->cn_flags & ISWHITEOUT) {
 				iswhiteout = 1;
@@ -321,8 +410,6 @@ union_lookup(ap)
 					iswhiteout = 1;
 			}
 		}
-	} else {
-		uerror = ENOENT;
 	}
 
 	/*
@@ -332,13 +419,14 @@ union_lookup(ap)
 	 * back from the upper layer and return the lower vnode
 	 * instead.
 	 */
+
 	if (lowerdvp != NULLVP && !iswhiteout) {
 		int nameiop;
 
-		vn_lock(lowerdvp, LK_EXCLUSIVE | LK_RETRY, p);
+		UDEBUG(("B %p\n", lowerdvp));
 
 		/*
-		 * Only do a LOOKUP on the bottom node, since
+		 * Force only LOOKUPs on the lower node, since
 		 * we won't be making changes to it anyway.
 		 */
 		nameiop = cnp->cn_nameiop;
@@ -347,42 +435,42 @@ union_lookup(ap)
 			saved_cred = cnp->cn_cred;
 			cnp->cn_cred = um->um_cred;
 		}
+
 		/*
 		 * We shouldn't have to worry about locking interactions
 		 * between the lower layer and our union layer (w.r.t.
 		 * `..' processing) because we don't futz with lowervp
 		 * locks in the union-node instantiation code path.
+		 *
+		 * union_lookup1() requires lowervp to be locked on entry,
+		 * and it will be unlocked on return.  The ref count will
+		 * not change.  On return lowervp doesn't represent anything
+		 * to us so we NULL it out.
 		 */
-		lerror = union_lookup1(um->um_lowervp, &lowerdvp,
-				&lowervp, cnp);
+		VREF(lowerdvp);
+		vn_lock(lowerdvp, LK_EXCLUSIVE | LK_RETRY, p);
+		lerror = union_lookup1(um->um_lowervp, &lowerdvp, &lowervp, cnp);
+		if (lowerdvp == lowervp)
+			vrele(lowerdvp);
+		else
+			vput(lowerdvp);
+		lowerdvp = NULL;	/* lowerdvp invalid after vput */
+
 		if (um->um_op == UNMNT_BELOW)
 			cnp->cn_cred = saved_cred;
 		cnp->cn_nameiop = nameiop;
 
-		if (lowervp != lowerdvp)
-			VOP_UNLOCK(lowerdvp, 0, p);
-
 		if (cnp->cn_consume != 0 || lerror == EACCES) {
-			if (lerror == EACCES)
-				lowervp = NULLVP;
-			if (uppervp != NULLVP) {
-				if (uppervp == upperdvp)
-					vrele(uppervp);
-				else
-					vput(uppervp);
-				uppervp = NULLVP;
+			if ((error = lerror) == 0) {
+				*ap->a_vpp = lowervp;
+				lowervp = NULL;
 			}
-			*ap->a_vpp = lowervp;
-			if (!lockparent)
-				cnp->cn_flags &= ~LOCKPARENT;
-			error = lerror;
 			goto out;
 		}
 	} else {
-		lerror = ENOENT;
+		UDEBUG(("C %p\n", lowerdvp));
 		if ((cnp->cn_flags & ISDOTDOT) && dun->un_pvp != NULLVP) {
-			lowervp = LOWERVP(dun->un_pvp);
-			if (lowervp != NULLVP) {
+			if ((lowervp = LOWERVP(dun->un_pvp)) != NULL) {
 				VREF(lowervp);
 				vn_lock(lowervp, LK_EXCLUSIVE | LK_RETRY, p);
 				lerror = 0;
@@ -390,35 +478,27 @@ union_lookup(ap)
 		}
 	}
 
-	if (!lockparent)
-		cnp->cn_flags &= ~LOCKPARENT;
-
 	/*
-	 * at this point, we have uerror and lerror indicating
-	 * possible errors with the lookups in the upper and lower
-	 * layers.  additionally, uppervp and lowervp are (locked)
-	 * references to existing vnodes in the upper and lower layers.
+	 * Ok.  Now we have uerror, uppervp, upperdvp, lerror, and lowervp.
+	 *
+	 * 1. If both layers returned an error, select the upper layer.
 	 *
-	 * there are now three cases to consider.
-	 * 1. if both layers returned an error, then return whatever
-	 *    error the upper layer generated.
+	 * 2. If the upper layer faile and the bottom layer succeeded,
+	 *    two subcases occur:
 	 *
-	 * 2. if the top layer failed and the bottom layer succeeded
-	 *    then two subcases occur.
-	 *    a.  the bottom vnode is not a directory, in which
-	 *	  case just return a new union vnode referencing
-	 *	  an empty top layer and the existing bottom layer.
-	 *    b.  the bottom vnode is a directory, in which case
-	 *	  create a new directory in the top-level and
-	 *	  continue as in case 3.
+	 *	a.  The bottom vnode is not a directory, in which case
+	 *	    just return a new union vnode referencing an
+	 *	    empty top layer and the existing bottom layer.
 	 *
-	 * 3. if the top layer succeeded then return a new union
+	 *	b.  The button vnode is a directory, in which case
+	 *	    create a new directory in the top layer and
+	 *	    and fall through to case 3.
+	 *
+	 * 3. If the top layer succeeded then return a new union
 	 *    vnode referencing whatever the new top layer and
 	 *    whatever the bottom layer returned.
 	 */
 
-	*ap->a_vpp = NULLVP;
-
 	/* case 1. */
 	if ((uerror != 0) && (lerror != 0)) {
 		error = uerror;
@@ -428,59 +508,126 @@ union_lookup(ap)
 	/* case 2. */
 	if (uerror != 0 /* && (lerror == 0) */ ) {
 		if (lowervp->v_type == VDIR) { /* case 2b. */
-			dun->un_flags &= ~UN_ULOCK;
-			VOP_UNLOCK(upperdvp, 0, p);
+			KASSERT(uppervp == NULL, ("uppervp unexpectedly non-NULL"));
+			/*
+			 * oops, uppervp has a problem, we may have to shadow.
+			 */
 			uerror = union_mkshadow(um, upperdvp, cnp, &uppervp);
-			vn_lock(upperdvp, LK_EXCLUSIVE | LK_RETRY, p);
-			dun->un_flags |= UN_ULOCK;
-
 			if (uerror) {
-				if (lowervp != NULLVP) {
-					vput(lowervp);
-					lowervp = NULLVP;
-				}
 				error = uerror;
 				goto out;
 			}
 		}
 	}
 
-	if (lowervp != NULLVP)
+	/*
+	 * Must call union_allocvp with both the upper and lower vnodes
+	 * referenced and the upper vnode locked.   ap->a_vpp is returned 
+	 * referenced and locked.  lowervp, uppervp, and upperdvp are 
+	 * absorbed by union_allocvp() whether it succeeds or fails.
+	 *
+	 * upperdvp is the parent directory of uppervp which may be
+	 * different, depending on the path, from dvp->un_uppervp.  That's
+	 * why it is a separate argument.  Note that it must be unlocked.
+	 *
+	 * dvp must be locked on entry to the call and will be locked on
+	 * return.
+	 */
+
+	if (uppervp && uppervp != upperdvp)
+		VOP_UNLOCK(uppervp, 0, p);
+	if (lowervp)
 		VOP_UNLOCK(lowervp, 0, p);
+	if (upperdvp)
+		VOP_UNLOCK(upperdvp, 0, p);
 
 	error = union_allocvp(ap->a_vpp, dvp->v_mount, dvp, upperdvp, cnp,
 			      uppervp, lowervp, 1);
 
-	if (error) {
-		if (uppervp != NULLVP)
-			vput(uppervp);
-		if (lowervp != NULLVP)
-			vrele(lowervp);
-	} else {
-		if (*ap->a_vpp != dvp)
-			if (!lockparent || !(cnp->cn_flags & ISLASTCN))
-				VOP_UNLOCK(dvp, 0, p);
-#ifdef DIAGNOSTIC
-        if (cnp->cn_namelen == 1 &&
-            cnp->cn_nameptr[0] == '.' &&
-            *ap->a_vpp != dvp) {
-            panic("union_lookup returning . (%p) not same as startdir (%p)",
-				  ap->a_vpp, dvp);
+	UDEBUG(("Create %p = %p %p refs=%d\n", *ap->a_vpp, uppervp, lowervp, (*ap->a_vpp) ? ((*ap->a_vpp)->v_usecount) : -99));
+
+	uppervp = NULL;
+	upperdvp = NULL;
+	lowervp = NULL;
+
+	/* 
+	 *	Termination Code
+	 *
+	 *	- put away any extra junk laying around.  Note that lowervp
+	 *	  (if not NULL) will never be the same as *ap->a_vp and 
+	 *	  neither will uppervp, because when we set that state we 
+	 *	  NULL-out lowervp or uppervp.  On the otherhand, upperdvp
+	 *	  may match uppervp or *ap->a_vpp.
+	 *
+	 *	- relock/unlock dvp if appropriate.
+	 */
+
+out:
+	if (upperdvp) {
+		if (upperdvp == uppervp || upperdvp == *ap->a_vpp)
+			vrele(upperdvp);
+		else
+			vput(upperdvp);
+	}
+
+	if (uppervp)
+		vput(uppervp);
+
+	if (lowervp)
+		vput(lowervp);
+
+	/*
+	 * Restore LOCKPARENT state
+	 */
+
+	if (!lockparent)
+		cnp->cn_flags &= ~LOCKPARENT;
+
+	UDEBUG(("Out %d vpp %p/%d lower %p upper %p\n", error, *ap->a_vpp,
+		((*ap->a_vpp) ? (*ap->a_vpp)->v_usecount : -99),
+		lowervp, uppervp));
+
+	/*
+	 * dvp lock state, determine whether to relock dvp.  dvp is expected
+	 * to be locked on return if:
+	 *
+	 *	- there was an error (except not EJUSTRETURN), or
+	 *	- we hit the last component and lockparent is true
+	 *
+	 * dvp_is_locked is the current state of the dvp lock, not counting
+	 * the possibility that *ap->a_vpp == dvp (in which case it is locked
+	 * anyway).  Note that *ap->a_vpp == dvp only if no error occured.
+	 */
+
+	if (*ap->a_vpp != dvp) {
+		if ((error == 0 || error == EJUSTRETURN) &&
+		    (!lockparent || (cnp->cn_flags & ISLASTCN) == 0)) {
+			VOP_UNLOCK(dvp, 0, p);
 		}
-#endif
 	}
 
-out:
-    if (cnp->cn_flags & ISDOTDOT) {
-        if (upperdvp != NULL)
-            vrele(upperdvp);
-        if (lowerdvp != NULL)
-            vrele(lowerdvp);
-    }
+	/*
+	 * Diagnostics
+	 */
+
+#ifdef DIAGNOSTIC
+	if (cnp->cn_namelen == 1 &&
+	    cnp->cn_nameptr[0] == '.' &&
+	    *ap->a_vpp != dvp) {
+		panic("union_lookup returning . (%p) not same as startdir (%p)", ap->a_vpp, dvp);
+	}
+#endif
 
 	return (error);
 }
 
+/*
+ * 	union_create:
+ *
+ * a_dvp is locked on entry and remains locked on return.  a_vpp is returned
+ * locked if no error occurs, otherwise it is garbage.
+ */
+
 static int
 union_create(ap)
 	struct vop_create_args /* {
@@ -491,36 +638,27 @@ union_create(ap)
 	} */ *ap;
 {
 	struct union_node *dun = VTOUNION(ap->a_dvp);
-	struct vnode *dvp = dun->un_uppervp;
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *dvp;
+	int error = EROFS;
 
-	if (dvp != NULLVP) {
+	if ((dvp = union_lock_upper(dun, p)) != NULL) {
 		struct vnode *vp;
 		struct mount *mp;
-		int error;
 
-		FIXUP(dun, p);
-
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
 		error = VOP_CREATE(dvp, &vp, cnp, ap->a_vap);
-		if (error) {
-			dun->un_flags |= UN_ULOCK;
-			return (error);
+		if (error == 0) {
+			mp = ap->a_dvp->v_mount;
+			VOP_UNLOCK(vp, 0, p);
+			UDEBUG(("ALLOCVP-1 FROM %p REFS %d\n", vp, vp->v_usecount));
+			error = union_allocvp(ap->a_vpp, mp, NULLVP, NULLVP,
+				cnp, vp, NULLVP, 1);
+			UDEBUG(("ALLOCVP-2B FROM %p REFS %d\n", *ap->a_vpp, vp->v_usecount));
 		}
-
-		mp = ap->a_dvp->v_mount;
-		VOP_UNLOCK(dvp, 0, p);
-		error = union_allocvp(ap->a_vpp, mp, NULLVP, NULLVP, cnp, vp,
-				NULLVP, 1);
-		if (error)
-			vput(vp);
-		vn_lock(ap->a_dvp, LK_EXCLUSIVE| LK_RETRY, p);
-		return (error);
+		union_unlock_upper(dvp, p);
 	}
-
-	return (EROFS);
+	return (error);
 }
 
 static int
@@ -533,15 +671,23 @@ union_whiteout(ap)
 {
 	struct union_node *un = VTOUNION(ap->a_dvp);
 	struct componentname *cnp = ap->a_cnp;
-	struct proc *p = cnp->cn_proc;
-
-	if (un->un_uppervp == NULLVP)
-		return (EOPNOTSUPP);
+	struct vnode *uppervp;
+	int error = EOPNOTSUPP;
 
-	FIXUP(un, p);
-	return (VOP_WHITEOUT(un->un_uppervp, cnp, ap->a_flags));
+	if ((uppervp = union_lock_upper(un, cnp->cn_proc)) != NULLVP) {
+		error = VOP_WHITEOUT(un->un_uppervp, cnp, ap->a_flags);
+		union_unlock_upper(uppervp, cnp->cn_proc);
+	}
+	return(error);
 }
 
+/*
+ * 	union_mknod:
+ *
+ *	a_dvp is locked on entry and should remain locked on return.
+ *	a_vpp is garbagre whether an error occurs or not.
+ */
+
 static int
 union_mknod(ap)
 	struct vop_mknod_args /* {
@@ -552,42 +698,28 @@ union_mknod(ap)
 	} */ *ap;
 {
 	struct union_node *dun = VTOUNION(ap->a_dvp);
-	struct vnode *dvp = dun->un_uppervp;
 	struct componentname *cnp = ap->a_cnp;
-	struct proc *p = cnp->cn_proc;
+	struct vnode *dvp;
+	int error = EROFS;
 
-	if (dvp != NULLVP) {
+	if ((dvp = union_lock_upper(dun, cnp->cn_proc)) != NULL) {
 		struct vnode *vp;
-		struct mount *mp;
-		int error;
-
-		FIXUP(dun, p);
-
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
 		error = VOP_MKNOD(dvp, &vp, cnp, ap->a_vap);
-		if (error) {
-			dun->un_flags |= UN_ULOCK;
-			return (error);
-		}
-
-		if (vp != NULLVP) {
-			mp = ap->a_dvp->v_mount;
-			VOP_UNLOCK(dvp, 0, p);
-			error = union_allocvp(ap->a_vpp, mp, NULLVP, NULLVP,
-					cnp, vp, NULLVP, 1);
-			if (error)
-				vput(vp);
-			vn_lock(ap->a_dvp, LK_EXCLUSIVE| LK_RETRY, p);
-		} else {
-			dun->un_flags |= UN_ULOCK;
-		}
-		return (error);
+		/* vp is garbage whether an error occurs or not */
+		union_unlock_upper(dvp, cnp->cn_proc);
 	}
-
-	return (EROFS);
+	return (error);
 }
 
+/*
+ *	union_open:
+ *
+ *	run open VOP.  When opening the underlying vnode we have to mimic
+ *	vn_open.  What we *really* need to do to avoid screwups if the
+ *	open semantics change is to call vn_open().  For example, ufs blows
+ *	up if you open a file but do not vmio it prior to writing.
+ */
+
 static int
 union_open(ap)
 	struct vop_open_args /* {
@@ -603,13 +735,18 @@ union_open(ap)
 	int mode = ap->a_mode;
 	struct ucred *cred = ap->a_cred;
 	struct proc *p = ap->a_p;
-	int error;
+	int error = 0;
+	int tvpisupper = 1;
 
 	/*
 	 * If there is an existing upper vp then simply open that.
+	 * The upper vp takes precedence over the lower vp.  When opening
+	 * a lower vp for writing copy it to the uppervp and then open the
+	 * uppervp.
+	 *
+	 * At the end of this section tvp will be left locked.
 	 */
-	tvp = un->un_uppervp;
-	if (tvp == NULLVP) {
+	if ((tvp = union_lock_upper(un, p)) == NULLVP) {
 		/*
 		 * If the lower vnode is being opened for writing, then
 		 * copy the file contents to the upper vnode and open that,
@@ -617,30 +754,50 @@ union_open(ap)
 		 */
 		tvp = un->un_lowervp;
 		if ((ap->a_mode & FWRITE) && (tvp->v_type == VREG)) {
-			error = union_copyup(un, (mode&O_TRUNC) == 0, cred, p);
-			if (error == 0)
-				error = VOP_OPEN(un->un_uppervp, mode, cred, p);
-			return (error);
+			int docopy = !(mode & O_TRUNC);
+			error = union_copyup(un, docopy, cred, p);
+			tvp = union_lock_upper(un, p);
+		} else {
+			un->un_openl++;
+			VREF(tvp);
+			vn_lock(tvp, LK_EXCLUSIVE | LK_RETRY, p);
+			tvpisupper = 0;
 		}
-
-		/*
-		 * Just open the lower vnode
-		 */
-		un->un_openl++;
-		vn_lock(tvp, LK_EXCLUSIVE | LK_RETRY, p);
-		error = VOP_OPEN(tvp, mode, cred, p);
-		VOP_UNLOCK(tvp, 0, p);
-
-		return (error);
 	}
 
-	FIXUP(un, p);
+	/*
+	 * We are holding the correct vnode, open it
+	 */
 
-	error = VOP_OPEN(tvp, mode, cred, p);
+	if (error == 0)
+		error = VOP_OPEN(tvp, mode, cred, p);
 
+	/*
+	 * Absolutely necessary or UFS will blowup
+	 */
+        if (error == 0 && vn_canvmio(tvp) == TRUE) {
+                error = vfs_object_create(tvp, p, cred);
+        }
+
+	/*
+	 * Release any locks held
+	 */
+	if (tvpisupper) {
+		if (tvp)
+			union_unlock_upper(tvp, p);
+	} else {
+		vput(tvp);
+	}
 	return (error);
 }
 
+/*
+ *	union_close:
+ *
+ *	It is unclear whether a_vp is passed locked or unlocked.  Whatever
+ *	the case we do not change it.
+ */
+
 static int
 union_close(ap)
 	struct vop_close_args /* {
@@ -661,7 +818,6 @@ union_close(ap)
 		--un->un_openl;
 		vp = un->un_lowervp;
 	}
-
 	ap->a_vp = vp;
 	return (VCALL(vp, VOFFSET(vop_close), ap));
 }
@@ -688,12 +844,12 @@ union_access(ap)
 	struct proc *p = ap->a_p;
 	int error = EACCES;
 	struct vnode *vp;
-	struct vnode *savedvp;
 
 	/*
 	 * Disallow write attempts on filesystems mounted read-only.
 	 */
-	if (ap->a_mode & VWRITE && (ap->a_vp->v_mount->mnt_flag & MNT_RDONLY)) {
+	if ((ap->a_mode & VWRITE) && 
+	    (ap->a_vp->v_mount->mnt_flag & MNT_RDONLY)) {
 		switch (ap->a_vp->v_type) {
 		case VREG: 
 		case VDIR:
@@ -703,19 +859,30 @@ union_access(ap)
 			break;
 		}
 	}
-	if ((vp = un->un_uppervp) != NULLVP) {
-		FIXUP(un, p);
+
+	if ((vp = union_lock_upper(un, p)) != NULLVP) {
 		ap->a_vp = vp;
-		return (VCALL(vp, VOFFSET(vop_access), ap));
+		error = VCALL(vp, VOFFSET(vop_access), ap);
+		union_unlock_upper(vp, p);
+		return(error);
 	}
 
 	if ((vp = un->un_lowervp) != NULLVP) {
 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-		savedvp = ap->a_vp;
 		ap->a_vp = vp;
+
+		/*
+		 * Remove VWRITE from a_mode if our mount point is RW, because
+		 * we want to allow writes and lowervp may be read-only.
+		 */
+		if ((un->un_vnode->v_mount->mnt_flag & MNT_RDONLY) == 0)
+			ap->a_mode &= ~VWRITE;
+
 		error = VCALL(vp, VOFFSET(vop_access), ap);
 		if (error == 0) {
-			struct union_mount *um = MOUNTTOUNIONMOUNT(savedvp->v_mount);
+			struct union_mount *um;
+
+			um = MOUNTTOUNIONMOUNT(un->un_vnode->v_mount);
 
 			if (um->um_op == UNMNT_BELOW) {
 				ap->a_cred = um->um_cred;
@@ -723,17 +890,26 @@ union_access(ap)
 			}
 		}
 		VOP_UNLOCK(vp, 0, p);
-		if (error)
-			return (error);
 	}
-
-	return (error);
+	return(error);
 }
 
 /*
  * We handle getattr only to change the fsid and
  * track object sizes
+ *
+ * It's not clear whether VOP_GETATTR is to be
+ * called with the vnode locked or not.  stat() calls
+ * it with (vp) locked, and fstat calls it with
+ * (vp) unlocked. 
+ *
+ * Because of this we cannot use our normal locking functions
+ * if we do not intend to lock the main a_vp node.  At the moment
+ * we are running without any specific locking at all, but beware
+ * to any programmer that care must be taken if locking is added
+ * to this function.
  */
+
 static int
 union_getattr(ap)
 	struct vop_getattr_args /* {
@@ -745,12 +921,10 @@ union_getattr(ap)
 {
 	int error;
 	struct union_node *un = VTOUNION(ap->a_vp);
-	struct vnode *vp = un->un_uppervp;
-	struct proc *p = ap->a_p;
+	struct vnode *vp;
 	struct vattr *vap;
 	struct vattr va;
 
-
 	/*
 	 * Some programs walk the filesystem hierarchy by counting
 	 * links to directories to avoid stat'ing all the time.
@@ -762,22 +936,11 @@ union_getattr(ap)
 
 	vap = ap->a_vap;
 
-	vp = un->un_uppervp;
-	if (vp != NULLVP) {
-		/*
-		 * It's not clear whether VOP_GETATTR is to be
-		 * called with the vnode locked or not.  stat() calls
-		 * it with (vp) locked, and fstat calls it with
-		 * (vp) unlocked.
-		 * In the mean time, compensate here by checking
-		 * the union_node's lock flag.
-		 */
-		if (un->un_flags & UN_LOCKED)
-			FIXUP(un, p);
-
+	if ((vp = un->un_uppervp) != NULLVP) {
 		error = VOP_GETATTR(vp, vap, ap->a_cred, ap->a_p);
 		if (error)
 			return (error);
+		/* XXX isn't this dangerouso without a lock? */
 		union_newsize(ap->a_vp, vap->va_size, VNOVAL);
 	}
 
@@ -794,12 +957,12 @@ union_getattr(ap)
 		error = VOP_GETATTR(vp, vap, ap->a_cred, ap->a_p);
 		if (error)
 			return (error);
+		/* XXX isn't this dangerous without a lock? */
 		union_newsize(ap->a_vp, VNOVAL, vap->va_size);
 	}
 
 	if ((vap != ap->a_vap) && (vap->va_type == VDIR))
 		ap->a_vap->va_nlink += vap->va_nlink;
-
 	return (0);
 }
 
@@ -815,27 +978,28 @@ union_setattr(ap)
 	struct union_node *un = VTOUNION(ap->a_vp);
 	struct proc *p = ap->a_p;
 	struct vattr *vap = ap->a_vap;
+	struct vnode *uppervp;
 	int error;
 
 	/*
 	 * Disallow write attempts on filesystems mounted read-only.
 	 */
 	if ((ap->a_vp->v_mount->mnt_flag & MNT_RDONLY) &&
-		(vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
-		 vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
-		 vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL))
+	    (vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
+	     vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
+	     vap->va_mtime.tv_sec != VNOVAL || 
+	     vap->va_mode != (mode_t)VNOVAL)) {
 		return (EROFS);
+	}
 
 	/*
 	 * Handle case of truncating lower object to zero size,
 	 * by creating a zero length upper object.  This is to
 	 * handle the case of open with O_TRUNC and O_CREAT.
 	 */
-	if ((un->un_uppervp == NULLVP) &&
-	    /* assert(un->un_lowervp != NULLVP) */
-	    (un->un_lowervp->v_type == VREG)) {
+	if (un->un_uppervp == NULLVP && (un->un_lowervp->v_type == VREG)) {
 		error = union_copyup(un, (ap->a_vap->va_size != 0),
-						ap->a_cred, ap->a_p);
+			    ap->a_cred, ap->a_p);
 		if (error)
 			return (error);
 	}
@@ -844,19 +1008,45 @@ union_setattr(ap)
 	 * Try to set attributes in upper layer,
 	 * otherwise return read-only filesystem error.
 	 */
-	if (un->un_uppervp != NULLVP) {
-		FIXUP(un, p);
+	error = EROFS;
+	if ((uppervp = union_lock_upper(un, p)) != NULLVP) {
 		error = VOP_SETATTR(un->un_uppervp, ap->a_vap,
 					ap->a_cred, ap->a_p);
 		if ((error == 0) && (ap->a_vap->va_size != VNOVAL))
 			union_newsize(ap->a_vp, ap->a_vap->va_size, VNOVAL);
-	} else {
-		error = EROFS;
+		union_unlock_upper(uppervp, p);
 	}
-
 	return (error);
 }
 
+/*
+ *	union_getpages:
+ */
+
+static int
+union_getpages(struct vop_getpages_args *ap)
+{
+	int r;
+
+	r = vnode_pager_generic_getpages(ap->a_vp, ap->a_m, 
+		ap->a_count, ap->a_reqpage);
+	return(r);
+}
+
+/*
+ *	union_putpages:
+ */
+
+static int
+union_putpages(struct vop_putpages_args *ap)
+{
+	int r;
+
+	r = vnode_pager_generic_putpages(ap->a_vp, ap->a_m, ap->a_count,
+		ap->a_sync, ap->a_rtvals);
+	return(r);
+}
+
 static int
 union_read(ap)
 	struct vop_read_args /* {
@@ -866,18 +1056,19 @@ union_read(ap)
 		struct ucred *a_cred;
 	} */ *ap;
 {
-	int error;
+	struct union_node *un = VTOUNION(ap->a_vp);
 	struct proc *p = ap->a_uio->uio_procp;
-	struct vnode *vp = OTHERVP(ap->a_vp);
-	int dolock = (vp == LOWERVP(ap->a_vp));
+	struct vnode *uvp;
+	int error;
 
-	if (dolock)
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-	else
-		FIXUP(VTOUNION(ap->a_vp), p);
-	error = VOP_READ(vp, ap->a_uio, ap->a_ioflag, ap->a_cred);
-	if (dolock)
-		VOP_UNLOCK(vp, 0, p);
+	uvp = union_lock_other(un, p);
+	KASSERT(uvp != NULL, ("union_read: backing vnode missing!"));
+
+	if (ap->a_vp->v_flag & VOBJBUF)
+		union_vm_coherency(ap->a_vp, ap->a_uio, 0);
+
+	error = VOP_READ(uvp, ap->a_uio, ap->a_ioflag, ap->a_cred);
+	union_unlock_other(uvp, p);
 
 	/*
 	 * XXX
@@ -889,7 +1080,7 @@ union_read(ap)
 		struct union_node *un = VTOUNION(ap->a_vp);
 		off_t cur = ap->a_uio->uio_offset;
 
-		if (vp == un->un_uppervp) {
+		if (uvp == un->un_uppervp) {
 			if (cur > un->un_uppersz)
 				union_newsize(ap->a_vp, cur, VNOVAL);
 		} else {
@@ -897,7 +1088,6 @@ union_read(ap)
 				union_newsize(ap->a_vp, VNOVAL, cur);
 		}
 	}
-
 	return (error);
 }
 
@@ -910,17 +1100,36 @@ union_write(ap)
 		struct ucred *a_cred;
 	} */ *ap;
 {
-	int error;
-	struct vnode *vp;
 	struct union_node *un = VTOUNION(ap->a_vp);
 	struct proc *p = ap->a_uio->uio_procp;
+	struct vnode *uppervp;
+	int error;
 
-	vp = UPPERVP(ap->a_vp);
-	if (vp == NULLVP)
+	if ((uppervp = union_lock_upper(un, p)) == NULLVP)
 		panic("union: missing upper layer in write");
 
-	FIXUP(un, p);
-	error = VOP_WRITE(vp, ap->a_uio, ap->a_ioflag, ap->a_cred);
+	/*
+	 * Since our VM pages are associated with our vnode rather then
+	 * the real vnode, and since we do not run our reads and writes 
+	 * through our own VM cache, we have a VM/VFS coherency problem. 
+	 * We solve them by invalidating or flushing the associated VM
+	 * pages prior to allowing a normal read or write to occur.
+	 *
+	 * VM-backed writes (UIO_NOCOPY) have to be converted to normal
+	 * writes because we are not cache-coherent.  Normal writes need
+	 * to be made coherent with our VM-backing store, which we do by
+	 * first flushing any dirty VM pages associated with the write
+	 * range, and then destroying any clean VM pages associated with
+	 * the write range.
+	 */
+
+	if (ap->a_uio->uio_segflg == UIO_NOCOPY) {
+		ap->a_uio->uio_segflg = UIO_SYSSPACE;
+	} else if (ap->a_vp->v_flag & VOBJBUF) {
+		union_vm_coherency(ap->a_vp, ap->a_uio, 1);
+	}
+
+	error = VOP_WRITE(uppervp, ap->a_uio, ap->a_ioflag, ap->a_cred);
 
 	/*
 	 * the size of the underlying object may be changed by the
@@ -932,7 +1141,7 @@ union_write(ap)
 		if (cur > un->un_uppersz)
 			union_newsize(ap->a_vp, cur, VNOVAL);
 	}
-
+	union_unlock_upper(uppervp, p);
 	return (error);
 }
 
@@ -945,7 +1154,7 @@ union_lease(ap)
 		int a_flag;
 	} */ *ap;
 {
-	register struct vnode *ovp = OTHERVP(ap->a_vp);
+	struct vnode *ovp = OTHERVP(ap->a_vp);
 
 	ap->a_vp = ovp;
 	return (VCALL(ovp, VOFFSET(vop_lease), ap));
@@ -962,7 +1171,7 @@ union_ioctl(ap)
 		struct proc *a_p;
 	} */ *ap;
 {
-	register struct vnode *ovp = OTHERVP(ap->a_vp);
+	struct vnode *ovp = OTHERVP(ap->a_vp);
 
 	ap->a_vp = ovp;
 	return (VCALL(ovp, VOFFSET(vop_ioctl), ap));
@@ -977,7 +1186,7 @@ union_poll(ap)
 		struct proc *a_p;
 	} */ *ap;
 {
-	register struct vnode *ovp = OTHERVP(ap->a_vp);
+	struct vnode *ovp = OTHERVP(ap->a_vp);
 
 	ap->a_vp = ovp;
 	return (VCALL(ovp, VOFFSET(vop_poll), ap));
@@ -1010,7 +1219,7 @@ union_mmap(ap)
 		struct proc *a_p;
 	} */ *ap;
 {
-	register struct vnode *ovp = OTHERVP(ap->a_vp);
+	struct vnode *ovp = OTHERVP(ap->a_vp);
 
 	ap->a_vp = ovp;
 	return (VCALL(ovp, VOFFSET(vop_mmap), ap));
@@ -1027,35 +1236,24 @@ union_fsync(ap)
 {
 	int error = 0;
 	struct proc *p = ap->a_p;
-	struct vnode *targetvp = OTHERVP(ap->a_vp);
-	struct union_node *un;
-
-	if (targetvp != NULLVP) {
-		int dolock = (targetvp == LOWERVP(ap->a_vp));
-
-		un = VTOUNION(ap->a_vp);
-		if (dolock)
-			vn_lock(targetvp, LK_EXCLUSIVE | LK_RETRY, p);
-		else  {
-			un = VTOUNION(ap->a_vp);
-			if ((un->un_flags & UN_ULOCK) == 0 &&
-			    targetvp->v_data != NULL &&
-			    ((struct lock *)targetvp->v_data)->lk_lockholder
-			        == curproc->p_pid &&
-			    VOP_ISLOCKED(targetvp) != 0)
-				return 0;   /* XXX */
-
-			FIXUP(un, p);
-		}
+	struct vnode *targetvp;
+	struct union_node *un = VTOUNION(ap->a_vp);
 
+	if ((targetvp = union_lock_other(un, p)) != NULLVP) {
 		error = VOP_FSYNC(targetvp, ap->a_cred, ap->a_waitfor, p);
-		if (dolock)
-			VOP_UNLOCK(targetvp, 0, p);
+		union_unlock_other(targetvp, p);
 	}
 
 	return (error);
 }
 
+/*
+ *	union_remove:
+ *
+ *	Remove the specified cnp.  The dvp and vp are passed to us locked
+ *	and must remain locked on return.
+ */
+
 static int
 union_remove(ap)
 	struct vop_remove_args /* {
@@ -1068,42 +1266,40 @@ union_remove(ap)
 	struct union_node *un = VTOUNION(ap->a_vp);
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *uppervp;
+	struct vnode *upperdvp;
 	int error;
 
-	if (dun->un_uppervp == NULLVP)
+	if ((upperdvp = union_lock_upper(dun, p)) == NULLVP)
 		panic("union remove: null upper vnode");
 
-	if (un->un_uppervp != NULLVP) {
-		struct vnode *dvp = dun->un_uppervp;
-		struct vnode *vp = un->un_uppervp;
-
-		FIXUP(dun, p);
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
-		FIXUP(un, p);
-		un->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_vp, 0, p);
-
+	if ((uppervp = union_lock_upper(un, p)) != NULLVP) {
 		if (union_dowhiteout(un, cnp->cn_cred, p))
 			cnp->cn_flags |= DOWHITEOUT;
-		error = VOP_REMOVE(dvp, vp, cnp);
+		error = VOP_REMOVE(upperdvp, uppervp, cnp);
 #if 0
 		/* XXX */
 		if (!error)
 			union_removed_upper(un);
 #endif
-		dun->un_flags |= UN_ULOCK;
-		un->un_flags |= UN_ULOCK;
+		union_unlock_upper(uppervp, p);
 	} else {
-		FIXUP(dun, p);
 		error = union_mkwhiteout(
-			MOUNTTOUNIONMOUNT(UNIONTOV(dun)->v_mount),
-			dun->un_uppervp, ap->a_cnp, un->un_path);
+			    MOUNTTOUNIONMOUNT(ap->a_dvp->v_mount),
+			    upperdvp, ap->a_cnp, un->un_path);
 	}
-
+	union_unlock_upper(upperdvp, p);
 	return (error);
 }
 
+/*
+ *	union_link:
+ *
+ *	tdvp will be locked on entry, vp will not be locked on entry.
+ *	tdvp should remain locked on return and vp should remain unlocked
+ *	on return.
+ */
+
 static int
 union_link(ap)
 	struct vop_link_args /* {
@@ -1119,43 +1315,56 @@ union_link(ap)
 	struct vnode *tdvp;
 	int error = 0;
 
-
 	if (ap->a_tdvp->v_op != ap->a_vp->v_op) {
 		vp = ap->a_vp;
 	} else {
 		struct union_node *tun = VTOUNION(ap->a_vp);
+
 		if (tun->un_uppervp == NULLVP) {
 			vn_lock(ap->a_vp, LK_EXCLUSIVE | LK_RETRY, p);
+#if 0
 			if (dun->un_uppervp == tun->un_dirvp) {
-				dun->un_flags &= ~UN_ULOCK;
-				VOP_UNLOCK(dun->un_uppervp, 0, p);
+				if (dun->un_flags & UN_ULOCK) {
+					dun->un_flags &= ~UN_ULOCK;
+					VOP_UNLOCK(dun->un_uppervp, 0, p);
+				}
 			}
+#endif
 			error = union_copyup(tun, 1, cnp->cn_cred, p);
+#if 0
 			if (dun->un_uppervp == tun->un_dirvp) {
 				vn_lock(dun->un_uppervp,
-						LK_EXCLUSIVE | LK_RETRY, p);
+					    LK_EXCLUSIVE | LK_RETRY, p);
 				dun->un_flags |= UN_ULOCK;
 			}
+#endif
 			VOP_UNLOCK(ap->a_vp, 0, p);
 		}
 		vp = tun->un_uppervp;
 	}
 
-	tdvp = dun->un_uppervp;
-	if (tdvp == NULLVP)
-		error = EROFS;
-
 	if (error)
 		return (error);
 
-	FIXUP(dun, p);
-	dun->un_flags |= UN_KLOCK;
-	VOP_UNLOCK(ap->a_tdvp, 0, p);
+	/*
+	 * Make sure upper is locked, then unlock the union directory we were 
+	 * called with to avoid a deadlock while we are calling VOP_LINK on 
+	 * the upper (with tdvp locked and vp not locked).  Our ap->a_tdvp
+	 * is expected to be locked on return.
+	 */
 
-	error = VOP_LINK(tdvp, vp, cnp);
+	if ((tdvp = union_lock_upper(dun, p)) == NULLVP)
+		return (EROFS);
 
-	dun->un_flags |= UN_ULOCK;
+	VOP_UNLOCK(ap->a_tdvp, 0, p);		/* unlock calling node */
+	error = VOP_LINK(tdvp, vp, cnp);	/* call link on upper */
 
+	/*
+	 * We have to unlock tdvp prior to relocking our calling node in
+	 * order to avoid a deadlock.
+	 */
+	union_unlock_upper(tdvp, p);
+	vn_lock(ap->a_tdvp, LK_EXCLUSIVE | LK_RETRY, p);
 	return (error);
 }
 
@@ -1171,12 +1380,16 @@ union_rename(ap)
 	} */ *ap;
 {
 	int error;
-
 	struct vnode *fdvp = ap->a_fdvp;
 	struct vnode *fvp = ap->a_fvp;
 	struct vnode *tdvp = ap->a_tdvp;
 	struct vnode *tvp = ap->a_tvp;
 
+	/*
+	 * Figure out what fdvp to pass to our upper or lower vnode.  If we
+	 * replace the fdvp, release the original one and ref the new one.
+	 */
+
 	if (fdvp->v_op == union_vnodeop_p) {	/* always true */
 		struct union_node *un = VTOUNION(fdvp);
 		if (un->un_uppervp == NULLVP) {
@@ -1189,30 +1402,77 @@ union_rename(ap)
 			error = EXDEV;
 			goto bad;
 		}
-
 		fdvp = un->un_uppervp;
 		VREF(fdvp);
 		vrele(ap->a_fdvp);
 	}
 
+	/*
+	 * Figure out what fvp to pass to our upper or lower vnode.  If we
+	 * replace the fvp, release the original one and ref the new one.
+	 */
+
 	if (fvp->v_op == union_vnodeop_p) {	/* always true */
 		struct union_node *un = VTOUNION(fvp);
+#if 0
+		struct union_mount *um = MOUNTTOUNIONMOUNT(fvp->v_mount);
+#endif
+
 		if (un->un_uppervp == NULLVP) {
-			/* XXX: should do a copyup */
-			error = EXDEV;
-			goto bad;
+			switch(fvp->v_type) {
+			case VREG:
+				vn_lock(un->un_vnode, LK_EXCLUSIVE | LK_RETRY, ap->a_fcnp->cn_proc);
+				error = union_copyup(un, 1, ap->a_fcnp->cn_cred, ap->a_fcnp->cn_proc);
+				VOP_UNLOCK(un->un_vnode, 0, ap->a_fcnp->cn_proc);
+				if (error)
+					goto bad;
+				break;
+			case VDIR:
+				/*
+				 * XXX not yet.
+				 *
+				 * There is only one way to rename a directory
+				 * based in the lowervp, and that is to copy
+				 * the entire directory hierarchy.  Otherwise
+				 * it would not last across a reboot.
+				 */
+#if 0
+				vrele(fvp);
+				fvp = NULL;
+				vn_lock(fdvp, LK_EXCLUSIVE | LK_RETRY, ap->a_fcnp->cn_proc);
+				error = union_mkshadow(um, fdvp, 
+					    ap->a_fcnp, &un->un_uppervp);
+				VOP_UNLOCK(fdvp, 0, ap->a_fcnp->cn_proc);
+				if (un->un_uppervp)
+					VOP_UNLOCK(un->un_uppervp, 0, ap->a_fcnp->cn_proc);
+				if (error)
+					goto bad;
+				break;
+#endif
+			default:
+				error = EXDEV;
+				goto bad;
+			}
 		}
 
 		if (un->un_lowervp != NULLVP)
 			ap->a_fcnp->cn_flags |= DOWHITEOUT;
-
 		fvp = un->un_uppervp;
 		VREF(fvp);
 		vrele(ap->a_fvp);
 	}
 
+	/*
+	 * Figure out what tdvp (destination directory) to pass to the
+	 * lower level.  If we replace it with uppervp, we need to vput the 
+	 * old one.  The exclusive lock is transfered to what we will pass
+	 * down in the VOP_RENAME and we replace uppervp with a simple
+	 * reference.
+	 */
+
 	if (tdvp->v_op == union_vnodeop_p) {
 		struct union_node *un = VTOUNION(tdvp);
+
 		if (un->un_uppervp == NULLVP) {
 			/*
 			 * this should never happen in normal
@@ -1224,32 +1484,52 @@ union_rename(ap)
 			goto bad;
 		}
 
-		tdvp = un->un_uppervp;
-		VREF(tdvp);
-		un->un_flags |= UN_KLOCK;
+		/*
+		 * new tdvp is a lock and reference on uppervp, put away
+		 * the old tdvp.
+		 */
+		tdvp = union_lock_upper(un, ap->a_tcnp->cn_proc);
 		vput(ap->a_tdvp);
 	}
 
+	/*
+	 * Figure out what tvp (destination file) to pass to the
+	 * lower level.
+	 *
+	 * If the uppervp file does not exist put away the (wrong)
+	 * file and change tvp to NULL.
+	 */
+
 	if (tvp != NULLVP && tvp->v_op == union_vnodeop_p) {
 		struct union_node *un = VTOUNION(tvp);
 
-		tvp = un->un_uppervp;
-		if (tvp != NULLVP) {
-			VREF(tvp);
-			un->un_flags |= UN_KLOCK;
-		}
+		tvp = union_lock_upper(un, ap->a_tcnp->cn_proc);
 		vput(ap->a_tvp);
+		/* note: tvp may be NULL */
 	}
 
+	/*
+	 * VOP_RENAME releases/vputs prior to returning, so we have no
+	 * cleanup to do.
+	 */
+
 	return (VOP_RENAME(fdvp, fvp, ap->a_fcnp, tdvp, tvp, ap->a_tcnp));
 
+	/*
+	 * Error.  We still have to release / vput the various elements.
+	 */
+
 bad:
 	vrele(fdvp);
-	vrele(fvp);
+	if (fvp)
+		vrele(fvp);
 	vput(tdvp);
-	if (tvp != NULLVP)
-		vput(tvp);
-
+	if (tvp != NULLVP) {
+		if (tvp != tdvp)
+			vput(tvp);
+		else
+			vrele(tvp);
+	}
 	return (error);
 }
 
@@ -1263,34 +1543,26 @@ union_mkdir(ap)
 	} */ *ap;
 {
 	struct union_node *dun = VTOUNION(ap->a_dvp);
-	struct vnode *dvp = dun->un_uppervp;
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *upperdvp;
+	int error = EROFS;
 
-	if (dvp != NULLVP) {
+	if ((upperdvp = union_lock_upper(dun, p)) != NULLVP) {
 		struct vnode *vp;
-		int error;
-
-		FIXUP(dun, p);
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
-		error = VOP_MKDIR(dvp, &vp, cnp, ap->a_vap);
-		if (error) {
-			dun->un_flags |= UN_ULOCK;
-			return (error);
-		}
 
-		VOP_UNLOCK(dvp, 0, p);
-		error = union_allocvp(ap->a_vpp, ap->a_dvp->v_mount, ap->a_dvp,
-				NULLVP, cnp, vp, NULLVP, 1);
-		if (error)
-			vput(vp);
-		vn_lock(ap->a_dvp, LK_EXCLUSIVE| LK_RETRY, p);
+		error = VOP_MKDIR(upperdvp, &vp, cnp, ap->a_vap);
+		union_unlock_upper(upperdvp, p);
 
-		return (error);
+		if (error == 0) {
+			VOP_UNLOCK(vp, 0, p);
+			UDEBUG(("ALLOCVP-2 FROM %p REFS %d\n", vp, vp->v_usecount));
+			error = union_allocvp(ap->a_vpp, ap->a_dvp->v_mount,
+				ap->a_dvp, NULLVP, cnp, vp, NULLVP, 1);
+			UDEBUG(("ALLOCVP-2B FROM %p REFS %d\n", *ap->a_vpp, vp->v_usecount));
+		}
 	}
-
-	return (EROFS);
+	return (error);
 }
 
 static int
@@ -1305,42 +1577,34 @@ union_rmdir(ap)
 	struct union_node *un = VTOUNION(ap->a_vp);
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *upperdvp;
+	struct vnode *uppervp;
 	int error;
 
-	if (dun->un_uppervp == NULLVP)
+	if ((upperdvp = union_lock_upper(dun, p)) == NULLVP)
 		panic("union rmdir: null upper vnode");
 
-	if (un->un_uppervp != NULLVP) {
-		struct vnode *dvp = dun->un_uppervp;
-		struct vnode *vp = un->un_uppervp;
-
-		FIXUP(dun, p);
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
-		FIXUP(un, p);
-		un->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_vp, 0, p);
-
+	if ((uppervp = union_lock_upper(un, p)) != NULLVP) {
 		if (union_dowhiteout(un, cnp->cn_cred, p))
 			cnp->cn_flags |= DOWHITEOUT;
-		error = VOP_RMDIR(dvp, vp, ap->a_cnp);
-#if 0
-		/* XXX */
-		if (!error)
-			union_removed_upper(un);
-#endif
-		dun->un_flags |= UN_ULOCK;
-		un->un_flags |= UN_ULOCK;
+		error = VOP_RMDIR(upperdvp, uppervp, ap->a_cnp);
+		union_unlock_upper(uppervp, p);
 	} else {
-		FIXUP(dun, p);
 		error = union_mkwhiteout(
-			MOUNTTOUNIONMOUNT(UNIONTOV(dun)->v_mount),
-			dun->un_uppervp, ap->a_cnp, un->un_path);
+			    MOUNTTOUNIONMOUNT(ap->a_dvp->v_mount),
+			    dun->un_uppervp, ap->a_cnp, un->un_path);
 	}
-
+	union_unlock_upper(upperdvp, p);
 	return (error);
 }
 
+/*
+ *	union_symlink:
+ *
+ *	dvp is locked on entry and remains locked on return.  a_vpp is garbage
+ *	(unused).
+ */
+
 static int
 union_symlink(ap)
 	struct vop_symlink_args /* {
@@ -1352,24 +1616,20 @@ union_symlink(ap)
 	} */ *ap;
 {
 	struct union_node *dun = VTOUNION(ap->a_dvp);
-	struct vnode *dvp = dun->un_uppervp;
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
+	struct vnode *dvp;
+	int error = EROFS;
 
-	if (dvp != NULLVP) {
+	if ((dvp = union_lock_upper(dun, p)) != NULLVP) {
 		struct vnode *vp;
-		int error;
 
-		FIXUP(dun, p);
-		dun->un_flags |= UN_KLOCK;
-		VOP_UNLOCK(ap->a_dvp, 0, p);
 		error = VOP_SYMLINK(dvp, &vp, cnp, ap->a_vap, ap->a_target);
-		dun->un_flags |= UN_ULOCK;
+		/* vp is garbage whether an error occurs or not */
 		*ap->a_vpp = NULLVP;
-		return (error);
+		union_unlock_upper(dvp, p);
 	}
-
-	return (EROFS);
+	return (error);
 }
 
 /*
@@ -1391,15 +1651,16 @@ union_readdir(ap)
 	} */ *ap;
 {
 	struct union_node *un = VTOUNION(ap->a_vp);
-	struct vnode *uvp = un->un_uppervp;
 	struct proc *p = ap->a_uio->uio_procp;
+	struct vnode *uvp;
+	int error = 0;
 
-	if (uvp == NULLVP)
-		return (0);
-
-	FIXUP(un, p);
-	ap->a_vp = uvp;
-	return (VCALL(uvp, VOFFSET(vop_readdir), ap));
+	if ((uvp = union_lock_upper(un, p)) != NULLVP) {
+		ap->a_vp = uvp;
+		error = VCALL(uvp, VOFFSET(vop_readdir), ap);
+		union_unlock_upper(uvp, p);
+	}
+	return(error);
 }
 
 static int
@@ -1411,23 +1672,28 @@ union_readlink(ap)
 	} */ *ap;
 {
 	int error;
+	struct union_node *un = VTOUNION(ap->a_vp);
 	struct uio *uio = ap->a_uio;
 	struct proc *p = uio->uio_procp;
-	struct vnode *vp = OTHERVP(ap->a_vp);
-	int dolock = (vp == LOWERVP(ap->a_vp));
+	struct vnode *vp;
+
+	vp = union_lock_other(un, p);
+	KASSERT(vp != NULL, ("union_readlink: backing vnode missing!"));
 
-	if (dolock)
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-	else
-		FIXUP(VTOUNION(ap->a_vp), p);
 	ap->a_vp = vp;
 	error = VCALL(vp, VOFFSET(vop_readlink), ap);
-	if (dolock)
-		VOP_UNLOCK(vp, 0, p);
+	union_unlock_other(vp, p);
 
 	return (error);
 }
 
+/*
+ *	union_abortop:
+ *
+ *	dvp is locked on entry and left locked on return
+ *
+ */
+
 static int
 union_abortop(ap)
 	struct vop_abortop_args /* {
@@ -1435,28 +1701,35 @@ union_abortop(ap)
 		struct componentname *a_cnp;
 	} */ *ap;
 {
-	int error;
 	struct componentname *cnp = ap->a_cnp;
 	struct proc *p = cnp->cn_proc;
-	struct vnode *vp = OTHERVP(ap->a_dvp);
 	struct union_node *un = VTOUNION(ap->a_dvp);
-	int islocked = un->un_flags & UN_LOCKED;
-	int dolock = (vp == LOWERVP(ap->a_dvp));
+	int islocked = VOP_ISLOCKED(ap->a_dvp);
+	struct vnode *vp;
+	int error;
 
 	if (islocked) {
-		if (dolock)
-			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-		else
-			FIXUP(VTOUNION(ap->a_dvp), p);
+		vp = union_lock_other(un, p);
+	} else {
+		vp = OTHERVP(ap->a_dvp);
 	}
+	KASSERT(vp != NULL, ("union_abortop: backing vnode missing!"));
+
 	ap->a_dvp = vp;
 	error = VCALL(vp, VOFFSET(vop_abortop), ap);
-	if (islocked && dolock)
-		VOP_UNLOCK(vp, 0, p);
+
+	if (islocked)
+		union_unlock_other(vp, p);
 
 	return (error);
 }
 
+/*
+ *	union_inactive:
+ *
+ *	Called with the vnode locked.  We are expected to unlock the vnode.
+ */
+
 static int
 union_inactive(ap)
 	struct vop_inactive_args /* {
@@ -1485,10 +1758,17 @@ union_inactive(ap)
 	if (un->un_dircache != 0) {
 		for (vpp = un->un_dircache; *vpp != NULLVP; vpp++)
 			vrele(*vpp);
-		free(un->un_dircache, M_TEMP);
+		free (un->un_dircache, M_TEMP);
 		un->un_dircache = 0;
 	}
 
+#if 0
+	if ((un->un_flags & UN_ULOCK) && un->un_uppervp) {
+		un->un_flags &= ~UN_ULOCK;
+		VOP_UNLOCK(un->un_uppervp, 0, p);
+	}
+#endif
+
 	VOP_UNLOCK(vp, 0, p);
 
 	if ((un->un_flags & UN_CACHED) == 0)
@@ -1503,7 +1783,6 @@ union_reclaim(ap)
 		struct vnode *a_vp;
 	} */ *ap;
 {
-
 	union_freevp(ap->a_vp);
 
 	return (0);
@@ -1513,75 +1792,47 @@ static int
 union_lock(ap)
 	struct vop_lock_args *ap;
 {
+#if 0
 	struct vnode *vp = ap->a_vp;
 	struct proc *p = ap->a_p;
 	int flags = ap->a_flags;
 	struct union_node *un;
+#endif
 	int error;
 
-	vop_nolock(ap);
-	/*
-	 * Need to do real lockmgr-style locking here.
-	 * in the mean time, draining won't work quite right,
-	 * which could lead to a few race conditions.
-	 * the following test was here, but is not quite right, we
-	 * still need to take the lock:
-	if ((flags & LK_TYPE_MASK) == LK_DRAIN)
-		return (0);
-	 */
-	flags &= ~LK_INTERLOCK;
-
-start:
+	error = vop_stdlock(ap);
+#if 0
 	un = VTOUNION(vp);
 
-	if (un->un_uppervp != NULLVP) {
-		if (((un->un_flags & UN_ULOCK) == 0) &&
-		    (vp->v_usecount != 0)) {
-			error = vn_lock(un->un_uppervp, flags, p);
-			if (error)
-				return (error);
-			un->un_flags |= UN_ULOCK;
-		}
-#ifdef DIAGNOSTIC
-		if (un->un_flags & UN_KLOCK) {
-			vprint("dangling upper lock", vp);
-			panic("union: dangling upper lock");
+	if (error == 0) {
+		/*
+		 * Lock the upper if it exists and this is an exclusive lock
+		 * request.
+		 */
+		if (un->un_uppervp != NULLVP && 
+		    (flags & LK_TYPE_MASK) == LK_EXCLUSIVE) {
+			if ((un->un_flags & UN_ULOCK) == 0 && vp->v_usecount) {
+				error = vn_lock(un->un_uppervp, flags, p);
+				if (error) {
+					struct vop_unlock_args uap = { 0 };
+					uap.a_vp = ap->a_vp;
+					uap.a_flags = ap->a_flags;
+					uap.a_p = ap->a_p;
+					vop_stdunlock(&uap);
+					return (error);
+				}
+				un->un_flags |= UN_ULOCK;
+			}
 		}
-#endif
 	}
-
-	if (un->un_flags & UN_LOCKED) {
-#ifdef DIAGNOSTIC
-		if (curproc && un->un_pid == curproc->p_pid &&
-			    un->un_pid > -1 && curproc->p_pid > -1)
-			panic("union: locking against myself");
-#endif
-		un->un_flags |= UN_WANT;
-		tsleep((caddr_t)&un->un_flags, PINOD, "unionlk2", 0);
-		goto start;
-	}
-
-#ifdef DIAGNOSTIC
-	if (curproc)
-		un->un_pid = curproc->p_pid;
-	else
-		un->un_pid = -1;
 #endif
-
-	un->un_flags |= UN_LOCKED;
-	return (0);
+	return (error);
 }
 
 /*
- * When operations want to vput() a union node yet retain a lock on
- * the upper vnode (say, to do some further operations like link(),
- * mkdir(), ...), they set UN_KLOCK on the union node, then call
- * vput() which calls VOP_UNLOCK() and comes here.  union_unlock()
- * unlocks the union node (leaving the upper vnode alone), clears the
- * KLOCK flag, and then returns to vput().  The caller then does whatever
- * is left to do with the upper vnode, and ensures that it gets unlocked.
+ *	union_unlock:
  *
- * If UN_KLOCK isn't set, then the upper vnode is unlocked here.
+ *	Unlock our union node.  This also unlocks uppervp.  
  */
 static int
 union_unlock(ap)
@@ -1592,36 +1843,38 @@ union_unlock(ap)
 	} */ *ap;
 {
 	struct union_node *un = VTOUNION(ap->a_vp);
-	struct proc *p = ap->a_p;
-
-#ifdef DIAGNOSTIC
-	if ((un->un_flags & UN_LOCKED) == 0)
-		panic("union: unlock unlocked node");
-	if (curproc && un->un_pid != curproc->p_pid &&
-			curproc->p_pid > -1 && un->un_pid > -1)
-		panic("union: unlocking other process's union node");
-#endif
+	int error;
 
-	un->un_flags &= ~UN_LOCKED;
+	KASSERT((un->un_uppervp == NULL || un->un_uppervp->v_usecount > 0), ("uppervp usecount is 0"));
 
-	if ((un->un_flags & (UN_ULOCK|UN_KLOCK)) == UN_ULOCK)
-		VOP_UNLOCK(un->un_uppervp, 0, p);
+	error = vop_stdunlock(ap);
+#if 0
 
-	un->un_flags &= ~(UN_ULOCK|UN_KLOCK);
+	/*
+	 * If no exclusive locks remain and we are holding an uppervp lock,
+	 * remove the uppervp lock.
+	 */
 
-	if (un->un_flags & UN_WANT) {
-		un->un_flags &= ~UN_WANT;
-		wakeup((caddr_t) &un->un_flags);
+	if ((un->un_flags & UN_ULOCK) && 
+	    lockstatus(&un->un_lock) != LK_EXCLUSIVE) {
+		un->un_flags &= ~UN_ULOCK;
+		VOP_UNLOCK(un->un_uppervp, LK_EXCLUSIVE, p);
 	}
-
-#ifdef DIAGNOSTIC
-	un->un_pid = 0;
 #endif
-	vop_nounlock(ap);
-
-	return (0);
+	return(error);
 }
 
+/*
+ *	union_bmap:
+ *
+ *	There isn't much we can do.  We cannot push through to the real vnode
+ *	to get to the underlying device because this will bypass data
+ *	cached by the real vnode.
+ *
+ *	For some reason we cannot return the 'real' vnode either, it seems
+ *	to blow up memory maps.
+ */
+
 static int
 union_bmap(ap)
 	struct vop_bmap_args /* {
@@ -1633,21 +1886,7 @@ union_bmap(ap)
 		int *a_runb;
 	} */ *ap;
 {
-	int error;
-	struct proc *p = curproc;		/* XXX */
-	struct vnode *vp = OTHERVP(ap->a_vp);
-	int dolock = (vp == LOWERVP(ap->a_vp));
-
-	if (dolock)
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-	else
-		FIXUP(VTOUNION(ap->a_vp), p);
-	ap->a_vp = vp;
-	error = VCALL(vp, VOFFSET(vop_bmap), ap);
-	if (dolock)
-		VOP_UNLOCK(vp, 0, p);
-
-	return (error);
+	return(EOPNOTSUPP);
 }
 
 static int
@@ -1669,16 +1908,6 @@ union_print(ap)
 }
 
 static int
-union_islocked(ap)
-	struct vop_islocked_args /* {
-		struct vnode *a_vp;
-	} */ *ap;
-{
-
-	return ((VTOUNION(ap->a_vp)->un_flags & UN_LOCKED) ? 1 : 0);
-}
-
-static int
 union_pathconf(ap)
 	struct vop_pathconf_args /* {
 		struct vnode *a_vp;
@@ -1688,17 +1917,15 @@ union_pathconf(ap)
 {
 	int error;
 	struct proc *p = curproc;		/* XXX */
-	struct vnode *vp = OTHERVP(ap->a_vp);
-	int dolock = (vp == LOWERVP(ap->a_vp));
+	struct union_node *un = VTOUNION(ap->a_vp);
+	struct vnode *vp;
+
+	vp = union_lock_other(un, p);
+	KASSERT(vp != NULL, ("union_pathconf: backing vnode missing!"));
 
-	if (dolock)
-		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
-	else
-		FIXUP(VTOUNION(ap->a_vp), p);
 	ap->a_vp = vp;
 	error = VCALL(vp, VOFFSET(vop_pathconf), ap);
-	if (dolock)
-		VOP_UNLOCK(vp, 0, p);
+	union_unlock_other(vp, p);
 
 	return (error);
 }
@@ -1722,6 +1949,8 @@ union_advlock(ap)
 
 /*
  * XXX - vop_strategy must be hand coded because it has no
+ * YYY - and it is not coherent with anything
+ *
  * vnode in its arguments.
  * This goes away with a merged VM/buffer cache.
  */
@@ -1742,7 +1971,6 @@ union_strategy(ap)
 	    (othervp == LOWERVP(bp->b_vp)))
 		panic("union_strategy: writing to lowervp");
 #endif
-
 	return (VOP_STRATEGY(othervp, bp));
 }
 
@@ -1759,10 +1987,12 @@ static struct vnodeopv_entry_desc union_vnodeop_entries[] = {
 	{ &vop_close_desc,		(vop_t *) union_close },
 	{ &vop_create_desc,		(vop_t *) union_create },
 	{ &vop_fsync_desc,		(vop_t *) union_fsync },
+	{ &vop_getpages_desc,		(vop_t *) union_getpages },
+	{ &vop_putpages_desc,		(vop_t *) union_putpages },
 	{ &vop_getattr_desc,		(vop_t *) union_getattr },
 	{ &vop_inactive_desc,		(vop_t *) union_inactive },
 	{ &vop_ioctl_desc,		(vop_t *) union_ioctl },
-	{ &vop_islocked_desc,		(vop_t *) union_islocked },
+	{ &vop_islocked_desc,		(vop_t *) vop_stdislocked },
 	{ &vop_lease_desc,		(vop_t *) union_lease },
 	{ &vop_link_desc,		(vop_t *) union_link },
 	{ &vop_lock_desc,		(vop_t *) union_lock },