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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 29 Feb 2012 15:18:04 +0000 (UTC)
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Subject: svn commit: r232304 - head/sys/fs/nullfs
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Author: kib
Date: Wed Feb 29 15:18:04 2012
New Revision: 232304
URL: http://svn.freebsd.org/changeset/base/232304

Log:
  Document that null_nodeget() cannot take shared-locked lowervp due to
  insmntque() requirements.
  
  Tested by:	pho
  MFC after:	1 week

Modified:
  head/sys/fs/nullfs/null_subr.c

Modified: head/sys/fs/nullfs/null_subr.c
==============================================================================
--- head/sys/fs/nullfs/null_subr.c	Wed Feb 29 15:15:36 2012	(r232303)
+++ head/sys/fs/nullfs/null_subr.c	Wed Feb 29 15:18:04 2012	(r232304)
@@ -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 */