--- sbin/mount_msdosfs/mount_msdosfs.c	2007-09-24 20:36:51.000000000 +0800
+++ sbin/mount_msdosfs/mount_msdosfs.c	2007-10-07 03:15:40.000000000 +0800
@@ -69,7 +69,7 @@ 
 	struct iovec *iov = NULL;
 	int iovlen = 0;
 	struct stat sb;
-	int c, mntflags, set_gid, set_uid, set_mask, set_dirmask;
+	int c, mntflags, set_gid, set_uid, set_mask, set_dirmask, update = 0;
 	char *dev, *dir, mntpath[MAXPATHLEN], *csp;
 	char fstype[] = "msdosfs";
 	char *cs_dos = NULL;
@@ -133,6 +133,7 @@ 
 				*p = '\0';
 				val = p + 1;
 			}
+			update = update || !strcmp(optarg, "update");
 			build_iovec(&iov, &iovlen, optarg, val, -1);
 			}
 			break;
@@ -165,13 +166,15 @@ 
 	if (optind + 2 != argc)
 		usage();
 
-	if (set_mask && !set_dirmask) {
-		dirmask = mask;
-		set_dirmask = 1;
-	}
-	else if (set_dirmask && !set_mask) {
-		mask = dirmask;
-		set_mask = 1;
+	if (!update) {
+		if (set_mask && !set_dirmask) {
+			dirmask = mask;
+			set_dirmask = 1;
+		}
+		else if (set_dirmask && !set_mask) {
+			mask = dirmask;
+			set_mask = 1;
+		}
 	}
 
 	dev = argv[optind];
@@ -195,26 +198,36 @@ 
 	(void)checkpath(dir, mntpath);
 	(void)rmslashes(dev, dev);
 
-	if (!set_gid || !set_uid || !set_mask) {
+	if (!update && (!set_gid || !set_uid || !set_mask)) {
 		if (stat(mntpath, &sb) == -1)
 			err(EX_OSERR, "stat %s", mntpath);
-
-		if (!set_uid)
+		if (!set_uid) {
 			uid = sb.st_uid;
-		if (!set_gid)
+			set_uid = 1;
+		}
+		if (!set_gid) {
 			gid = sb.st_gid;
-		if (!set_mask)
+			set_gid = 1;
+		}
+		if (!set_mask) {
 			mask = dirmask =
 				sb.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO);
+			set_mask = set_dirmask = 1;
+		}
 	}
 
 	build_iovec(&iov, &iovlen, "fstype", fstype, -1);
 	build_iovec(&iov, &iovlen, "fspath", mntpath, -1);
 	build_iovec(&iov, &iovlen, "from", dev, -1);
-	build_iovec_argf(&iov, &iovlen, "uid", "%d", uid);
-	build_iovec_argf(&iov, &iovlen, "gid", "%u", gid);
-	build_iovec_argf(&iov, &iovlen, "mask", "%u", mask);
-	build_iovec_argf(&iov, &iovlen, "dirmask", "%u", dirmask);
+	
+	if (set_uid)
+		build_iovec_argf(&iov, &iovlen, "uid", "%d", uid);
+	if (set_gid)
+		build_iovec_argf(&iov, &iovlen, "gid", "%u", gid);
+	if (set_mask)
+		build_iovec_argf(&iov, &iovlen, "mask", "%u", mask);
+	if (set_dirmask)
+		build_iovec_argf(&iov, &iovlen, "dirmask", "%u", dirmask);
 
 	if (nmount(iov, iovlen, mntflags) < 0)
 		err(1, "%s", dev);