diff -Nurw util-linux-ng-2.16.orig/mount/umount.c util-linux-ng-2.16/mount/umount.c
--- util-linux-ng-2.16.orig/mount/umount.c	2009-07-04 01:20:06.000000000 +0200
+++ util-linux-ng-2.16/mount/umount.c	2009-09-29 14:50:44.000000000 +0200
@@ -361,6 +361,7 @@
 umount_all (char *types, char *test_opts) {
      struct mntentchn *mc, *hd;
      int errors = 0;
+     int do_sync = 0;
 
      hd = mtab_head();
      if (!hd->prev)
@@ -370,9 +371,11 @@
 	      && matching_opts (mc->m.mnt_opts, test_opts)) {
 	       errors |= umount_one (mc->m.mnt_fsname, mc->m.mnt_dir,
 				     mc->m.mnt_type, mc->m.mnt_opts, mc);
+	       do_sync = 1;		     
 	  }
      }
 
+     if (do_sync)
      sync ();
      return errors;
 }