[src/trunk]: src/sys/ufs/ufs Add a comment describing an observed boom-crash-...

[pooka <pooka%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f931c102b3da
branches:  trunk
changeset: 755172:f931c102b3da
user:      pooka <pooka%NetBSD.org@localhost>
date:      Tue May 25 11:02:07 2010 +0000

description:
Add a comment describing an observed boom-crash-burn problem in
the code.  Fixing it will require a full tank of gas, half a pack
of cigarettes, sunglasses, darkness, and most importantly:
someone else.

diffstat:

 sys/ufs/ufs/ufs_wapbl.c |  8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diffs (29 lines):

diff -r 10ede2377a12 -r f931c102b3da sys/ufs/ufs/ufs_wapbl.c
--- a/sys/ufs/ufs/ufs_wapbl.c   Tue May 25 10:15:34 2010 +0000
+++ b/sys/ufs/ufs/ufs_wapbl.c   Tue May 25 11:02:07 2010 +0000
@@ -1,4 +1,4 @@
-/*  $NetBSD: ufs_wapbl.c,v 1.8 2010/03/02 14:45:55 pooka Exp $ */
+/*  $NetBSD: ufs_wapbl.c,v 1.9 2010/05/25 11:02:07 pooka Exp $ */
 
 /*-
  * Copyright (c) 2003,2006,2008 The NetBSD Foundation, Inc.
@@ -66,7 +66,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ufs_wapbl.c,v 1.8 2010/03/02 14:45:55 pooka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ufs_wapbl.c,v 1.9 2010/05/25 11:02:07 pooka Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -371,6 +371,10 @@
                error = ENOENT; /* XXX ufs_rename sets "0" here */
                goto out2;
        }
+       /*
+        * XXX: if fvp != a_fvp, a_fvp can now have 0 references and yet we
+        * access a_fvp->inode via ip later.  boom.
+        */
        vrele(ap->a_fvp);
 
        /* save directory lookup information in case tdvp == fdvp */