From 92a83dd9cf3ca4bce4dc21c0c1dbed85eb570724 Mon Sep 17 00:00:00 2001
From: joerg <joerg@NetBSD.org>
Date: Sun, 16 Nov 2008 19:34:19 +0000
Subject: [PATCH] Backout revision 1.212 and add a comment that short-cutting
 the WAPBL case is not possible. The buffer length has changed and the rounded
 size may not have, essentially changing the transaction size. Reported by
 various users and in PR 39898.

---
 sys/kern/vfs_bio.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 3f8bc032764c..80a8d63e261c 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: vfs_bio.c,v 1.213 2008/11/11 08:29:58 joerg Exp $	*/
+/*	$NetBSD: vfs_bio.c,v 1.214 2008/11/16 19:34:19 joerg Exp $	*/
 
 /*-
  * Copyright (c) 2007, 2008 The NetBSD Foundation, Inc.
@@ -109,7 +109,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.213 2008/11/11 08:29:58 joerg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_bio.c,v 1.214 2008/11/16 19:34:19 joerg Exp $");
 
 #include "fs_ffs.h"
 #include "opt_bufcache.h"
@@ -1267,8 +1267,14 @@ allocbuf(buf_t *bp, int size, int preserve)
 	bp->b_bcount = size;
 
 	oldsize = bp->b_bufsize;
-	if (oldsize == desired_size)
-		return 0;
+	if (oldsize == desired_size) {
+		/*
+		 * Do not short cut the WAPBL resize, as the buffer length
+		 * could still have changed and this would corrupt the
+		 * tracking of the transaction length.
+		 */
+		goto out;
+	}
 
 	/*
 	 * If we want a buffer of a different size, re-allocate the
@@ -1307,6 +1313,7 @@ allocbuf(buf_t *bp, int size, int preserve)
 	}
 	mutex_exit(&bufcache_lock);
 
+ out:
 	if (wapbl_vphaswapbl(bp->b_vp))
 		WAPBL_RESIZE_BUF(wapbl_vptomp(bp->b_vp), bp, oldsize, oldcount);