From c93d29a8f5f38b8c0c60239a2e70bc231ae69e20 Mon Sep 17 00:00:00 2001
From: Jan-Simon Pendry <pendry@ucbvax.Berkeley.EDU>
Date: Sun, 24 Apr 1994 15:46:47 -0800
Subject: [PATCH] detect root node and set VROOT flag

SCCS-vsn: sys/miscfs/union/union_subr.c 8.5
---
 usr/src/sys/miscfs/union/union_subr.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/usr/src/sys/miscfs/union/union_subr.c b/usr/src/sys/miscfs/union/union_subr.c
index 9e444c77ef..f0cd58e1d5 100644
--- a/usr/src/sys/miscfs/union/union_subr.c
+++ b/usr/src/sys/miscfs/union/union_subr.c
@@ -8,7 +8,7 @@
  *
  * %sccs.include.redist.c%
  *
- *	@(#)union_subr.c	8.4 (Berkeley) %G%
+ *	@(#)union_subr.c	8.5 (Berkeley) %G%
  */
 
 #include <sys/param.h>
@@ -21,6 +21,7 @@
 #include <sys/file.h>
 #include <sys/filedesc.h>
 #include <sys/queue.h>
+#include <sys/mount.h>
 #include <miscfs/union/union.h>
 
 #ifdef DIAGNOSTIC
@@ -200,7 +201,9 @@ union_allocvp(vpp, mp, undvp, dvp, cnp, uppervp, lowervp)
 	struct union_node *un;
 	struct union_node **pp;
 	struct vnode *xlowervp = NULLVP;
+	struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
 	int hash;
+	int vflag;
 	int try;
 
 	if (uppervp == NULLVP && lowervp == NULLVP)
@@ -211,6 +214,17 @@ union_allocvp(vpp, mp, undvp, dvp, cnp, uppervp, lowervp)
 		lowervp = NULLVP;
 	}
 
+	/* detect the root vnode (and aliases) */
+	vflag = 0;
+	if ((uppervp == um->um_uppervp) &&
+	    ((lowervp == NULLVP) || lowervp == um->um_lowervp)) {
+		if (lowervp == NULLVP) {
+			lowervp = um->um_lowervp;
+			VREF(lowervp);
+		}
+		vflag = VROOT;
+	}
+
 loop:
 	for (try = 0; try < 3; try++) {
 		switch (try) {
@@ -370,6 +384,7 @@ loop:
 	MALLOC((*vpp)->v_data, void *, sizeof(struct union_node),
 		M_TEMP, M_WAITOK);
 
+	(*vpp)->v_flag |= vflag;
 	if (uppervp)
 		(*vpp)->v_type = uppervp->v_type;
 	else
-- 
2.20.1