From owner-svn-src-head@FreeBSD.ORG  Wed May 21 03:11:27 2014
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id B57B8955;
 Wed, 21 May 2014 03:11:27 +0000 (UTC)
Received: from svn.freebsd.org (svn.freebsd.org
 [IPv6:2001:1900:2254:2068::e6a:0])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id A1DC720B5;
 Wed, 21 May 2014 03:11:27 +0000 (UTC)
Received: from svn.freebsd.org ([127.0.1.70])
 by svn.freebsd.org (8.14.8/8.14.8) with ESMTP id s4L3BRJJ047002;
 Wed, 21 May 2014 03:11:27 GMT (envelope-from bjk@svn.freebsd.org)
Received: (from bjk@localhost)
 by svn.freebsd.org (8.14.8/8.14.8/Submit) id s4L3BROu047001;
 Wed, 21 May 2014 03:11:27 GMT (envelope-from bjk@svn.freebsd.org)
Message-Id: <201405210311.s4L3BROu047001@svn.freebsd.org>
From: Benjamin Kaduk <bjk@FreeBSD.org>
Date: Wed, 21 May 2014 03:11:27 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: svn commit: r266482 - head/sys/kern
X-SVN-Group: head
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.18
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
 <svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head/>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 21 May 2014 03:11:27 -0000

Author: bjk (doc committer)
Date: Wed May 21 03:11:27 2014
New Revision: 266482
URL: http://svnweb.freebsd.org/changeset/base/266482

Log:
  Check for mismatched vref()/vdrop()
  
  Assert that the hold count has not fallen below the use count, a situation
  that would only happen when a vref() (or similar) is erroneously paired
  with a vdrop().  This situation has not been observed in the wild, but
  could be helpful for someone implementing a new filesystem.
  
  Reviewed by:	kib
  Approved by:	hrs (mentor)

Modified:
  head/sys/kern/vfs_subr.c

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Tue May 20 22:43:17 2014	(r266481)
+++ head/sys/kern/vfs_subr.c	Wed May 21 03:11:27 2014	(r266482)
@@ -2343,6 +2343,8 @@ vdropl(struct vnode *vp)
 	if (vp->v_holdcnt <= 0)
 		panic("vdrop: holdcnt %d", vp->v_holdcnt);
 	vp->v_holdcnt--;
+	VNASSERT(vp->v_holdcnt >= vp->v_usecount, vp,
+	    ("hold count less than use count"));
 	if (vp->v_holdcnt > 0) {
 		VI_UNLOCK(vp);
 		return;