From cca832bf9d799f80670b8c806b557b652a8b49b6 Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Fri, 2 Mar 2012 09:48:46 +0000
Subject: [PATCH] Do not expose unlocked unconstructed nullfs vnode on mount
 list. Lock the native nullfs vnode lock before switching the locks.

Tested by:	pho
MFC after:	1 week
---
 sys/fs/nullfs/null_subr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/fs/nullfs/null_subr.c b/sys/fs/nullfs/null_subr.c
index ae29bfccba7a..7e3571dcb47d 100644
--- a/sys/fs/nullfs/null_subr.c
+++ b/sys/fs/nullfs/null_subr.c
@@ -172,12 +172,12 @@ static void
 null_destroy_proto(struct vnode *vp, void *xp)
 {
 
+	lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
 	VI_LOCK(vp);
 	vp->v_data = NULL;
 	vp->v_vnlock = &vp->v_lock;
 	vp->v_op = &dead_vnodeops;
 	VI_UNLOCK(vp);
-	(void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	vgone(vp);
 	vput(vp);
 	free(xp, M_NULLFSNODE);