From 6717a2ac1b2c9927a883421b3a2451e8612d9a64 Mon Sep 17 00:00:00 2001
From: chs <chs@NetBSD.org>
Date: Mon, 8 Jan 2001 07:05:47 +0000
Subject: [PATCH] in vtruncbuf(), use a "synchronous freeing" flush to prevent
 a race between write i/os in a disk-based filesystem vs. the disk block being
 freed by a truncation, allocated to a new file, and written again with
 different data.  if the disk driver reorders the requests and does the second
 i/o first, the old data will clobber the new, corrupting the new file.

---
 sys/kern/vfs_subr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 310418e4e616..c5e7ca07274f 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: vfs_subr.c,v 1.143 2000/12/31 03:13:51 sommerfeld Exp $	*/
+/*	$NetBSD: vfs_subr.c,v 1.144 2001/01/08 07:05:47 chs Exp $	*/
 
 /*-
  * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc.
@@ -748,7 +748,7 @@ vtruncbuf(vp, lbn, slpflag, slptimeo)
 		simple_lock(&uobj->vmobjlock);
 		rv = (uobj->pgops->pgo_flush)(uobj,
 		    round_page(lbn << vp->v_mount->mnt_fs_bshift),
-		    vp->v_uvm.u_size, PGO_FREE);
+		    vp->v_uvm.u_size, PGO_FREE|PGO_SYNCIO);
 		simple_unlock(&uobj->vmobjlock);
 		if (!rv) {
 			splx(s);