diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c
index 0affad5..d4b5d38 100644
--- a/sys/kern/kern_lock.c
+++ b/sys/kern/kern_lock.c
@@ -54,6 +54,8 @@ __FBSDID("$FreeBSD$");
 #include <ddb/ddb.h>
 #endif
 
+#undef KTR_LOCK
+#define	KTR_LOCK	KTR_SUBSYS
 CTASSERT(((LK_ADAPTIVE | LK_NOSHARE) & LO_CLASSFLAGS) ==
     (LK_ADAPTIVE | LK_NOSHARE));
 CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
diff --git a/sys/nfsclient/nfs_subs.c b/sys/nfsclient/nfs_subs.c
index 6f4ef7b..5e12327 100644
--- a/sys/nfsclient/nfs_subs.c
+++ b/sys/nfsclient/nfs_subs.c
@@ -409,28 +409,25 @@ int
 nfs_upgrade_vnlock(struct vnode *vp)
 {
 	int old_lock;
-	
- 	if ((old_lock = VOP_ISLOCKED(vp)) != LK_EXCLUSIVE) {
- 		if (old_lock == LK_SHARED) {
- 			/* Upgrade to exclusive lock, this might block */
- 			vn_lock(vp, LK_UPGRADE | LK_RETRY);
- 		} else {
- 			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
- 		}
+
+	ASSERT_VOP_LOCKED(vp, "nfs_upgrade_vnlock");
+ 	old_lock = VOP_ISLOCKED(vp);
+	if (old_lock != LK_EXCLUSIVE) {
+ 		KASSERT(old_lock == LK_SHARED,
+		    ("nfs_upgrade_lock: wrong old_lock %d", old_lock));
+		/* Upgrade to exclusive lock, this might block */
+		vn_lock(vp, LK_UPGRADE | LK_RETRY);
   	}
-	return old_lock;
+	return (old_lock);
 }
 
 void
 nfs_downgrade_vnlock(struct vnode *vp, int old_lock)
 {
 	if (old_lock != LK_EXCLUSIVE) {
- 		if (old_lock == LK_SHARED) {
- 			/* Downgrade from exclusive lock, this might block */
- 			vn_lock(vp, LK_DOWNGRADE);
- 		} else {
- 			VOP_UNLOCK(vp, 0);
- 		}
+		KASSERT(old_lock == LK_SHARED, ("wrong old_lock %d", old_lock));
+		/* Downgrade from exclusive lock. */
+		vn_lock(vp, LK_DOWNGRADE);
   	}
 }
 
diff --git a/sys/sys/lock.h b/sys/sys/lock.h
index 9e47ab4..89c0d09 100644
--- a/sys/sys/lock.h
+++ b/sys/sys/lock.h
@@ -155,16 +155,16 @@ struct lock_class {
 
 #define	LOCK_LOG_LOCK(opname, lo, flags, recurse, file, line) do {	\
 	if (LOCK_LOG_TEST((lo), (flags)))				\
-		CTR5(KTR_LOCK, opname " (%s) %s r = %d at %s:%d",	\
+		CTR6(KTR_LOCK, opname " (%s) %s %p r = %d at %s:%d",	\
 		    LOCK_CLASS(lo)->lc_name, (lo)->lo_name,		\
-		    (u_int)(recurse), (file), (line));			\
+		    lo, (u_int)(recurse), (file), (line));		\
 } while (0)
 
 #define	LOCK_LOG_TRY(opname, lo, flags, result, file, line) do {	\
 	if (LOCK_LOG_TEST((lo), (flags)))				\
-		CTR5(KTR_LOCK, "TRY_" opname " (%s) %s result=%d at %s:%d",\
+		CTR6(KTR_LOCK, "TRY_" opname " (%s) %s %p result=%d at %s:%d",\
 		    LOCK_CLASS(lo)->lc_name, (lo)->lo_name,		\
-		    (u_int)(result), (file), (line));			\
+		    lo, (u_int)(result), (file), (line));		\
 } while (0)
 
 #define	LOCK_LOG_INIT(lo, flags) do {					\