Index: kern/vfs_cache.c
===================================================================
--- kern/vfs_cache.c	(revision 187408)
+++ kern/vfs_cache.c	(working copy)
@@ -607,6 +607,24 @@
 }
 
 /*
+ * Invalidate all negative entries for a particular directory vnode.
+ */
+void
+cache_purge_negative(vp)
+	struct vnode *vp;
+{
+	struct namecache *cp, *ncp;
+
+	CTR1(KTR_VFS, "cache_purge_negative(%p)", vp);
+	CACHE_LOCK();
+	LIST_FOREACH_SAFE(cp, &vp->v_cache_src, nc_src, ncp) {
+		if (cp->nc_vp == NULL)
+			cache_zap(cp);
+	}
+	CACHE_UNLOCK();
+}
+
+/*
  * Flush all entries referencing a particular filesystem.
  */
 void
Index: nfsclient/nfsnode.h
===================================================================
--- nfsclient/nfsnode.h	(revision 187408)
+++ nfsclient/nfsnode.h	(working copy)
@@ -109,6 +109,7 @@
 	time_t			n_modestamp;	/* mode cache timestamp */
 	struct timespec		n_mtime;	/* Prev modify time. */
 	time_t			n_ctime;	/* Prev create time. */
+	time_t			n_dmtime;	/* Prev dir modify time. */
 	time_t			n_expiry;	/* Lease expiry time */
 	nfsfh_t			*n_fhp;		/* NFS File Handle */
 	struct vnode		*n_vnode;	/* associated vnode */
Index: nfsclient/nfs_vnops.c
===================================================================
--- nfsclient/nfs_vnops.c	(revision 187408)
+++ nfsclient/nfs_vnops.c	(working copy)
@@ -594,13 +594,6 @@
 		    error = nfs_vinvalbuf(vp, V_SAVE, ap->a_td, 1);
 		mtx_lock(&np->n_mtx);
 	    }
- 	    /* 
- 	     * Invalidate the attribute cache in all cases.
- 	     * An open is going to fetch fresh attrs any way, other procs
- 	     * on this node that have file open will be forced to do an 
- 	     * otw attr fetch, but this is safe.
- 	     */
-	    np->n_attrstamp = 0;
 	    if (np->n_flag & NWRITEERR) {
 		np->n_flag &= ~NWRITEERR;
 		error = np->n_error;
@@ -648,12 +641,6 @@
 	 */
 	if (nfs_getattrcache(vp, ap->a_vap) == 0)
 		goto nfsmout;
-	if (v3 && nfsaccess_cache_timeout > 0) {
-		nfsstats.accesscache_misses++;
-		nfs3_access_otw(vp, NFSV3ACCESS_ALL, ap->a_td, ap->a_cred);
-		if (nfs_getattrcache(vp, ap->a_vap) == 0)
-			goto nfsmout;
-	}
 	nfsstats.rpccnt[NFSPROC_GETATTR]++;
 	mreq = nfsm_reqhead(vp, NFSPROC_GETATTR, NFSX_FH(v3));
 	mb = mreq;
@@ -844,6 +831,7 @@
 	struct componentname *cnp = ap->a_cnp;
 	struct vnode *dvp = ap->a_dvp;
 	struct vnode **vpp = ap->a_vpp;
+	struct vattr vattr;
 	int flags = cnp->cn_flags;
 	struct vnode *newvp;
 	struct nfsmount *nmp;
@@ -869,8 +857,12 @@
 		return (error);
 	}
 	if ((error = cache_lookup(dvp, vpp, cnp)) && error != ENOENT) {
-		struct vattr vattr;
-
+		/*
+		 * We only accept a positive hit in the cache if the
+		 * change time of the file matches our cached copy.
+		 * Otherwise, we discard the cache entry and fallback
+		 * to doing a lookup RPC.
+		 */
 		newvp = *vpp;
 		if (!VOP_GETATTR(newvp, &vattr, cnp->cn_cred, td)
 		 && vattr.va_ctime.tv_sec == VTONFS(newvp)->n_ctime) {
@@ -886,6 +878,24 @@
 		else 
 			vrele(newvp);
 		*vpp = NULLVP;
+	} else if (error == ENOENT) {
+		/*
+		 * We only accept a negative hit in the cache if the
+		 * modification time of the parent directory matches
+		 * our cached copy.  Otherwise, we discard all of the
+		 * negative cache entries for this directory.
+		 */
+		if (VOP_GETATTR(dvp, &vattr, cnp->cn_cred, td) == 0 &&
+		    vattr.va_mtime.tv_sec == np->n_dmtime) {
+			nfsstats.lookupcache_hits++;
+			if ((cnp->cn_nameiop == CREATE ||
+			    cnp->cn_nameiop == RENAME) &&
+			    (flags & ISLASTCN))
+				cnp->cn_flags |= SAVENAME;
+			return (ENOENT);
+		}
+		cache_purge_negative(dvp);
+		np->n_dmtime = 0;
 	}
 	error = 0;
 	newvp = NULLVP;
@@ -971,16 +981,38 @@
 			vput(newvp);
 			*vpp = NULLVP;
 		}
+
+		if (error != ENOENT)
+			goto done;
+
+		/* The requested file was not found. */
 		if ((cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME) &&
-		    (flags & ISLASTCN) && error == ENOENT) {
+		    (flags & ISLASTCN)) {
+			/*
+			 * XXX: UFS does a full VOP_ACCESS(dvp,
+			 * VWRITE) here instead of just checking
+			 * MNT_RDONLY.
+			 */
 			if (dvp->v_mount->mnt_flag & MNT_RDONLY)
-				error = EROFS;
-			else
-				error = EJUSTRETURN;
+				return (EROFS);
+			cnp->cn_flags |= SAVENAME;
+			return (EJUSTRETURN);
 		}
-		if (cnp->cn_nameiop != LOOKUP && (flags & ISLASTCN))
-			cnp->cn_flags |= SAVENAME;
+
+		if ((cnp->cn_flags & MAKEENTRY) && cnp->cn_nameiop != CREATE) {
+			/*
+			 * Maintain n_dmtime as the modification time
+			 * of the parent directory when the oldest -ve
+			 * name cache entry for this directory was
+			 * added.
+			 */
+			if (np->n_dmtime == 0)
+				np->n_dmtime = np->n_vattr.va_mtime.tv_sec;
+			cache_enter(dvp, NULL, cnp);
+		}
+		return (ENOENT);
 	}
+done:
 	return (error);
 }
 
Index: sys/vnode.h
===================================================================
--- sys/vnode.h	(revision 187408)
+++ sys/vnode.h	(working copy)
@@ -560,6 +560,7 @@
 int	cache_lookup(struct vnode *dvp, struct vnode **vpp,
 	    struct componentname *cnp);
 void	cache_purge(struct vnode *vp);
+void	cache_purge_negative(struct vnode *vp);
 void	cache_purgevfs(struct mount *mp);
 int	change_dir(struct vnode *vp, struct thread *td);
 int	change_root(struct vnode *vp, struct thread *td);