From 9ea303ddb816e8ac84f71251736e7cebeabd3b33 Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Wed, 29 Feb 2012 15:18:04 +0000
Subject: Document that null_nodeget() cannot take shared-locked lowervp due to
 insmntque() requirements.

Tested by:	pho
MFC after:	1 week
---
 sys/fs/nullfs/null_subr.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/sys/fs/nullfs/null_subr.c b/sys/fs/nullfs/null_subr.c
index 6bfae2c..ae29bfc 100644
--- a/sys/fs/nullfs/null_subr.c
+++ b/sys/fs/nullfs/null_subr.c
@@ -209,7 +209,11 @@ null_nodeget(mp, lowervp, vpp)
 	struct vnode *vp;
 	int error;
 
-	ASSERT_VOP_LOCKED(lowervp, "lowervp");
+	/*
+	 * The insmntque1() call below requires the exclusive lock on
+	 * the nullfs vnode.
+	 */
+	ASSERT_VOP_ELOCKED(lowervp, "lowervp");
 	KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p\n", lowervp));
 
 	/* Lookup the hash firstly */
-- 
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