From 9cbe5da9d536a29f6f9605fe8a87ffa680dc2406 Mon Sep 17 00:00:00 2001
From: Jeff Roberson <jeff@FreeBSD.org>
Date: Sun, 13 Mar 2005 12:04:12 +0000
Subject: [PATCH]  - It is not legal to access v_data without the vnode lock or
 interlock    held.  Grab the vnode interlock if LK_INTERLOCK has not been
 passed in    so that we can inspect v_data in ffs_lock().

Sponsored by:	Isilon Systems, Inc.
---
 sys/ufs/ffs/ffs_vnops.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/sys/ufs/ffs/ffs_vnops.c b/sys/ufs/ffs/ffs_vnops.c
index 9b3a440133c..03628767843 100644
--- a/sys/ufs/ffs/ffs_vnops.c
+++ b/sys/ufs/ffs/ffs_vnops.c
@@ -343,7 +343,17 @@ ffs_lock(ap)
 {
 	struct vnode *vp = ap->a_vp;
 
-	if ((VTOI(vp)->i_flags & SF_SNAPSHOT) &&
+	/*
+	 * v_data could be NULL if a thread attempts to lock a
+	 * vnode that is being recycled.  Just hit the normal
+	 * vnode lock in this case.  Grab the interlock so we may
+	 * safely inspect the vnode.
+	 */
+	if ((ap->a_flags & LK_INTERLOCK) == 0) {
+		VI_LOCK(vp);
+		ap->a_flags |= LK_INTERLOCK;
+	}
+	if (vp->v_data && (VTOI(vp)->i_flags & SF_SNAPSHOT) &&
 	    ((ap->a_flags & LK_TYPE_MASK) == LK_SHARED)) {
 		ap->a_flags &= ~LK_TYPE_MASK;
 		ap->a_flags |= LK_EXCLUSIVE;