The following reply was made to PR kern/32986; it has been noted by GNATS.

From: Jeff Ito <jeffito@speakeasy.net>
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: kern/32986
Date: Mon, 20 Mar 2006 14:24:55 -0500

 I've come up with this diff based on FreeBSD code, it rectifies the
 problem for me:
 
 Index: union_vfsops.c
 ===================================================================
 RCS file: /export/cvs/netbsd/src/sys/fs/union/union_vfsops.c,v
 retrieving revision 1.32
 diff -u -r1.32 union_vfsops.c
 --- union_vfsops.c      5 Jan 2006 20:31:33 -0000       1.32
 +++ union_vfsops.c      20 Mar 2006 19:20:18 -0000
 @@ -337,6 +337,7 @@
  {
         struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
         int freeing;
 +       int error;
 
  #ifdef UNION_DIAGNOSTIC
         printf("union_unmount(mp = %p)\n", mp);
 @@ -351,7 +352,7 @@
          * (d) times, where (d) is the maximum tree depth
          * in the filesystem.
          */
 -       for (freeing = 0; vflush(mp, NULL, 0) != 0;) {
 +       for (freeing = 0; (error = vflush(mp, NULL, 0)) != 0;) {
                 struct vnode *vp;
                 int n;
 
 @@ -374,8 +375,10 @@
          */
 
         if (mntflags & MNT_FORCE)
 -               vflush(mp, NULL, FORCECLOSE);
 +               error = vflush(mp, NULL, FORCECLOSE);
 
 +       if (error)
 +               return (error);
 
         /*
          * Discard references to upper and lower target vnodes.