Index: null_subr.c
===================================================================
--- null_subr.c	(revision 245340)
+++ null_subr.c	(working copy)
@@ -36,6 +36,7 @@
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/fnv_hash.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
@@ -46,8 +47,7 @@
 
 #include <fs/nullfs/null.h>
 
-#define LOG2_SIZEVNODE 8		/* log2(sizeof struct vnode) */
-#define	NNULLNODECACHE 16
+#define	NNULLNODECACHE 32767
 
 /*
  * Null layer cache:
@@ -57,8 +57,7 @@
  * alias is removed the lower vnode is vrele'd.
  */
 
-#define	NULL_NHASH(vp) \
-	(&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash])
+#define	NULL_NHASH(hash) (&null_node_hashtbl[(hash) & null_node_hash])
 
 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
 static u_long null_node_hash;
@@ -105,6 +104,7 @@
 	struct null_node_hashhead *hd;
 	struct null_node *a;
 	struct vnode *vp;
+	uint32_t hash;
 
 	ASSERT_VOP_LOCKED(lowervp, "null_hashget");
 
@@ -114,7 +114,8 @@
 	 * the lower vnode.  If found, the increment the null_node
 	 * reference count (but NOT the lower vnode's VREF counter).
 	 */
-	hd = NULL_NHASH(lowervp);
+	hash = fnv_32_buf(&lowervp, sizeof(lowervp), FNV1_32_INIT);
+	hd = NULL_NHASH(hash);
 	mtx_lock(&null_hashmtx);
 	LIST_FOREACH(a, hd, null_hash) {
 		if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
@@ -146,8 +147,10 @@
 	struct null_node_hashhead *hd;
 	struct null_node *oxp;
 	struct vnode *ovp;
+	uint32_t hash;
 
-	hd = NULL_NHASH(xp->null_lowervp);
+	hash = fnv_32_buf(&(xp->null_lowervp), sizeof(xp->null_lowervp), FNV1_32_INIT);
+	hd = NULL_NHASH(hash);
 	mtx_lock(&null_hashmtx);
 	LIST_FOREACH(oxp, hd, null_hash) {
 		if (oxp->null_lowervp == xp->null_lowervp &&