Index: sys/kern/vfs_lookup.c
===================================================================
--- sys/kern/vfs_lookup.c	(revision 205682)
+++ 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;
+		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;
-		}
-		if (cnp->cn_nameiop != LOOKUP) {
-			error = EISDIR;
+		case DELETE:
+		case RENAME:
+			error = EBUSY;
 			goto bad;
+		default:
+			KASSERT(cnp->cn_nameiop == LOOKUP,
+			    ("nameiop must be LOOKUP"));
 		}
 		if (wantparent) {
 			ndp->ni_dvp = dp;
Index: sys/kern/vfs_syscalls.c
===================================================================
--- sys/kern/vfs_syscalls.c	(revision 205679)
+++ sys/kern/vfs_syscalls.c	(working copy)
@@ -1746,8 +1746,10 @@ restart:
 	NDINIT(&nd, DELETE, LOCKPARENT | DOWHITEOUT | MPSAFE | AUDITVNODE1,
 	    UIO_USERSPACE, uap->path, td);
 	error = namei(&nd);
-	if (error)
-		return (error);
+	if (error) {
+		/* Translate error code for undelete("/"). */
+		return (error == EBUSY ? EEXIST : error);
+	}
 	vfslocked = NDHASGIANT(&nd);
 
 	if (nd.ni_vp != NULLVP || !(nd.ni_cnd.cn_flags & ISWHITEOUT)) {
@@ -1842,7 +1844,7 @@ 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) {
Index: sys/kern/vfs_vnops.c
===================================================================
--- sys/kern/vfs_vnops.c	(revision 205679)
+++ sys/kern/vfs_vnops.c	(working copy)
@@ -127,8 +127,10 @@ restart:
 		if (!(vn_open_flags & VN_OPEN_NOAUDIT))
 			ndp->ni_cnd.cn_flags |= AUDITVNODE1;
 		bwillwrite();
-		if ((error = namei(ndp)) != 0)
-			return (error);
+		if ((error = namei(ndp)) != 0) {
+			/* Translate error code for open("/", O_CREAT). */
+			return (error == EEXIST ? EISDIR : error);
+		}
 		vfslocked = NDHASGIANT(ndp);
 		if (!mpsafe)
 			ndp->ni_cnd.cn_flags &= ~MPSAFE;
Index: lib/libc/sys/rename.2
===================================================================
--- lib/libc/sys/rename.2	(revision 205679)
+++ lib/libc/sys/rename.2	(working copy)
@@ -28,7 +28,7 @@
 .\"     @(#)rename.2	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd April 10, 2008
+.Dd March 26, 2010
 .Dt RENAME 2
 .Os
 .Sh NAME
@@ -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 205679)
+++ lib/libc/sys/unlink.2	(working copy)
@@ -28,7 +28,7 @@
 .\"     @(#)unlink.2	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd April 10, 2008
+.Dd March 26, 2010
 .Dt UNLINK 2
 .Os
 .Sh NAME
@@ -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.
Index: share/man/man9/namei.9
===================================================================
--- share/man/man9/namei.9	(revision 205679)
+++ share/man/man9/namei.9	(working copy)
@@ -33,7 +33,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 21, 2005
+.Dd March 26, 2010
 .Os
 .Dt NAMEI 9
 .Sh NAME
@@ -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