Index: sys/kern/vfs_lookup.c
===================================================================
--- sys/kern/vfs_lookup.c	(revision 204620)
+++ sys/kern/vfs_lookup.c	(working copy)
@@ -565,18 +565,26 @@ dirloop:
 	}
 
 	/*
-	 * Check for degenerate name (e.g. / or "")
-	 * which is a way of talking about a directory,
-	 * e.g. like "/." or ".".
+	 * Check for "" which represents the root directory after slash
+	 * removal.
 	 */
 	if (cnp->cn_nameptr[0] == '\0') {
-		if (dp->v_type != VDIR) {
-			error = ENOTDIR;
-			goto bad;
-		}
-		if (cnp->cn_nameiop != LOOKUP) {
-			error = EISDIR;
-			goto bad;
+		KASSERT(dp->v_type == VDIR, ("dp is not a directory"));
+		/* 
+		 * We can't provide a parent node for CREATE,
+		 * DELETE and RENAME operations.
+		 */
+		switch (cnp->cn_nameiop) {
+		case CREATE:
+			error = EEXIST;
+			goto bad;
+		case DELETE:
+		case RENAME:
+			error = EBUSY;
+			goto bad;
+		default:
+			KASSERT(cnp->cn_nameiop == LOOKUP,
+			    ("nameiop must be LOOKUP"));
 		}
 		if (wantparent) {
 			ndp->ni_dvp = dp;
@@ -948,19 +956,17 @@ relookup(struct vnode *dvp, struct vnode
 #endif
 
 	/*
-	 * Check for degenerate name (e.g. / or "")
-	 * which is a way of talking about a directory,
-	 * e.g. like "/." or ".".
+	 * Check for "" which represents the root directory after slash
+	 * removal.
 	 */
 	if (cnp->cn_nameptr[0] == '\0') {
-		if (cnp->cn_nameiop != LOOKUP || wantparent) {
-			error = EISDIR;
-			goto bad;
-		}
-		if (dp->v_type != VDIR) {
-			error = ENOTDIR;
-			goto bad;
-		}
+		KASSERT(dp->v_type == VDIR, ("dp is not a directory"));
+		/*
+		 * Support only LOOKUP for "/" because lookup()
+		 * can't succeed for CREATE, DELETE and RENAME.
+		 */
+		KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP"));
+
 		if (!(cnp->cn_flags & LOCKLEAF))
 			VOP_UNLOCK(dp, 0);
 		*vpp = dp;
Index: sys/kern/vfs_syscalls.c
===================================================================
--- sys/kern/vfs_syscalls.c	(revision 204620)
+++ sys/kern/vfs_syscalls.c	(working copy)
@@ -1841,7 +1841,7 @@ restart:
 	NDINIT_AT(&nd, DELETE, LOCKPARENT | LOCKLEAF | MPSAFE | AUDITVNODE1,
 	    pathseg, path, fd, td);
 	if ((error = namei(&nd)) != 0)
-		return (error == EINVAL ? EPERM : error);
+		return ((error == EINVAL || error == EBUSY) ? EPERM : error);
 	vfslocked = NDHASGIANT(&nd);
 	vp = nd.ni_vp;
 	if (vp->v_type == VDIR && oldinum == 0) {
@@ -3617,9 +3617,6 @@ kern_renameat(struct thread *td, int old
 	if (fromnd.ni_vp->v_type == VDIR)
 		tond.ni_cnd.cn_flags |= WILLBEDIR;
 	if ((error = namei(&tond)) != 0) {
-		/* Translate error code for rename("dir1", "dir2/."). */
-		if (error == EISDIR && fvp->v_type == VDIR)
-			error = EINVAL;
 		NDFREE(&fromnd, NDF_ONLY_PNBUF);
 		vrele(fromnd.ni_dvp);
 		vrele(fvp);
Index: share/man/man9/namei.9
===================================================================
--- share/man/man9/namei.9	(revision 204620)
+++ share/man/man9/namei.9	(working copy)
@@ -338,8 +338,17 @@ An attempt is made to access a file in a
 permissions.
 .It Bq Er ELOOP
 Too many symbolic links were encountered in translating the pathname.
-.It Bq Er EISDIR
-An attempt is made to open a directory with write mode specified.
+.It Bq Er EINVAL
+The last component of the pathname specified for the RENAME operation is
+.Ql \&. .
+.It Bq Er EEXIST
+The root directory
+.Pq Ql /
+was specified for the CREATE operation.
+.It Bq Er EBUSY
+The root directory
+.Pq Ql /
+was specified for the DELETE operation.
 .It Bq Er EROFS
 An attempt is made to modify a file or directory on a read-only file system.
 .El
Index: lib/libc/sys/rename.2
===================================================================
--- lib/libc/sys/rename.2	(revision 204620)
+++ lib/libc/sys/rename.2	(working copy)
@@ -252,6 +252,12 @@ The
 .Fa to
 argument
 is a directory and is not empty.
+.It Bq Er EBUSY
+Either
+.Fa from
+or
+.Fa to
+is the root directory.
 .El
 .Pp
 In addition to the errors returned by the
Index: lib/libc/sys/unlink.2
===================================================================
--- lib/libc/sys/unlink.2	(revision 204620)
+++ lib/libc/sys/unlink.2	(working copy)
@@ -114,8 +114,6 @@ succeeds unless:
 .Bl -tag -width Er
 .It Bq Er ENOTDIR
 A component of the path prefix is not a directory.
-.It Bq Er EISDIR
-The named file is a directory.
 .It Bq Er ENAMETOOLONG
 A component of a pathname exceeded 255 characters,
 or an entire path name exceeded 1023 characters.