unsigned long nr_lock_classes;
 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 
+static inline struct lock_class *hlock_class(struct held_lock *hlock)
+{
+       if (!hlock->class_idx) {
+               DEBUG_LOCKS_WARN_ON(1);
+               return NULL;
+       }
+       return lock_classes + hlock->class_idx - 1;
+}
+
 #ifdef CONFIG_LOCK_STAT
 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
 
 
        holdtime = sched_clock() - hlock->holdtime_stamp;
 
-       stats = get_lock_stats(hlock->class);
+       stats = get_lock_stats(hlock_class(hlock));
        if (hlock->read)
                lock_time_inc(&stats->read_holdtime, holdtime);
        else
 
 static void print_lock(struct held_lock *hlock)
 {
-       print_lock_name(hlock->class);
+       print_lock_name(hlock_class(hlock));
        printk(", at: ");
        print_ip_sym(hlock->acquire_ip);
 }
        if (debug_locks_silent)
                return 0;
 
-       this.class = check_source->class;
+       this.class = hlock_class(check_source);
        if (!save_trace(&this.trace))
                return 0;
 
         * Check this lock's dependency list:
         */
        list_for_each_entry(entry, &source->locks_after, entry) {
-               if (entry->class == check_target->class)
+               if (entry->class == hlock_class(check_target))
                        return print_circular_bug_header(entry, depth+1);
                debug_atomic_inc(&nr_cyclic_checks);
                if (!check_noncircular(entry->class, depth+1))
                return 2;
        }
 
+       if (!source && debug_locks_off_graph_unlock()) {
+               WARN_ON(1);
+               return 0;
+       }
+
        /*
         * Check this lock's dependency list:
         */
        printk("\nand this task is already holding:\n");
        print_lock(prev);
        printk("which would create a new lock dependency:\n");
-       print_lock_name(prev->class);
+       print_lock_name(hlock_class(prev));
        printk(" ->");
-       print_lock_name(next->class);
+       print_lock_name(hlock_class(next));
        printk("\n");
 
        printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
 
        find_usage_bit = bit_backwards;
        /* fills in <backwards_match> */
-       ret = find_usage_backwards(prev->class, 0);
+       ret = find_usage_backwards(hlock_class(prev), 0);
        if (!ret || ret == 1)
                return ret;
 
        find_usage_bit = bit_forwards;
-       ret = find_usage_forwards(next->class, 0);
+       ret = find_usage_forwards(hlock_class(next), 0);
        if (!ret || ret == 1)
                return ret;
        /* ret == 2 */
 
        for (i = 0; i < curr->lockdep_depth; i++) {
                prev = curr->held_locks + i;
-               if (prev->class != next->class)
+               if (hlock_class(prev) != hlock_class(next))
                        continue;
                /*
                 * Allow read-after-read recursion of the same
         */
        check_source = next;
        check_target = prev;
-       if (!(check_noncircular(next->class, 0)))
+       if (!(check_noncircular(hlock_class(next), 0)))
                return print_circular_bug_tail();
 
        if (!check_prev_add_irq(curr, prev, next))
         *  chains - the second one will be new, but L1 already has
         *  L2 added to its dependency list, due to the first chain.)
         */
-       list_for_each_entry(entry, &prev->class->locks_after, entry) {
-               if (entry->class == next->class) {
+       list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
+               if (entry->class == hlock_class(next)) {
                        if (distance == 1)
                                entry->distance = 1;
                        return 2;
         * Ok, all validations passed, add the new lock
         * to the previous lock's dependency list:
         */
-       ret = add_lock_to_list(prev->class, next->class,
-                              &prev->class->locks_after, next->acquire_ip, distance);
+       ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
+                              &hlock_class(prev)->locks_after,
+                              next->acquire_ip, distance);
 
        if (!ret)
                return 0;
 
-       ret = add_lock_to_list(next->class, prev->class,
-                              &next->class->locks_before, next->acquire_ip, distance);
+       ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
+                              &hlock_class(next)->locks_before,
+                              next->acquire_ip, distance);
        if (!ret)
                return 0;
 
        /*
         * Debugging printouts:
         */
-       if (verbose(prev->class) || verbose(next->class)) {
+       if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
                graph_unlock();
                printk("\n new dependency: ");
-               print_lock_name(prev->class);
+               print_lock_name(hlock_class(prev));
                printk(" => ");
-               print_lock_name(next->class);
+               print_lock_name(hlock_class(next));
                printk("\n");
                dump_stack();
                return graph_lock();
                                     struct held_lock *hlock,
                                     u64 chain_key)
 {
-       struct lock_class *class = hlock->class;
+       struct lock_class *class = hlock_class(hlock);
        struct list_head *hash_head = chainhashentry(chain_key);
        struct lock_chain *chain;
        struct held_lock *hlock_curr, *hlock_next;
        if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
                chain->base = cn;
                for (j = 0; j < chain->depth - 1; j++, i++) {
-                       int lock_id = curr->held_locks[i].class - lock_classes;
+                       int lock_id = curr->held_locks[i].class_idx - 1;
                        chain_hlocks[chain->base + j] = lock_id;
                }
                chain_hlocks[chain->base + j] = class - lock_classes;
                        WARN_ON(1);
                        return;
                }
-               id = hlock->class - lock_classes;
+               id = hlock->class_idx - 1;
                if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
                        return;
 
        print_lock(this);
 
        printk("{%s} state was registered at:\n", usage_str[prev_bit]);
-       print_stack_trace(this->class->usage_traces + prev_bit, 1);
+       print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
 
        print_irqtrace_events(curr);
        printk("\nother info that might help us debug this:\n");
 valid_state(struct task_struct *curr, struct held_lock *this,
            enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
 {
-       if (unlikely(this->class->usage_mask & (1 << bad_bit)))
+       if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
                return print_usage_bug(curr, this, bad_bit, new_bit);
        return 1;
 }
        lockdep_print_held_locks(curr);
 
        printk("\nthe first lock's dependencies:\n");
-       print_lock_dependencies(this->class, 0);
+       print_lock_dependencies(hlock_class(this), 0);
 
        printk("\nthe second lock's dependencies:\n");
        print_lock_dependencies(other, 0);
 
        find_usage_bit = bit;
        /* fills in <forwards_match> */
-       ret = find_usage_forwards(this->class, 0);
+       ret = find_usage_forwards(hlock_class(this), 0);
        if (!ret || ret == 1)
                return ret;
 
 
        find_usage_bit = bit;
        /* fills in <backwards_match> */
-       ret = find_usage_backwards(this->class, 0);
+       ret = find_usage_backwards(hlock_class(this), 0);
        if (!ret || ret == 1)
                return ret;
 
                                LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
                        return 0;
 #endif
-               if (hardirq_verbose(this->class))
+               if (hardirq_verbose(hlock_class(this)))
                        ret = 2;
                break;
        case LOCK_USED_IN_SOFTIRQ:
                                LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
                        return 0;
 #endif
-               if (softirq_verbose(this->class))
+               if (softirq_verbose(hlock_class(this)))
                        ret = 2;
                break;
        case LOCK_USED_IN_HARDIRQ_READ:
                if (!check_usage_forwards(curr, this,
                                          LOCK_ENABLED_HARDIRQS, "hard"))
                        return 0;
-               if (hardirq_verbose(this->class))
+               if (hardirq_verbose(hlock_class(this)))
                        ret = 2;
                break;
        case LOCK_USED_IN_SOFTIRQ_READ:
                if (!check_usage_forwards(curr, this,
                                          LOCK_ENABLED_SOFTIRQS, "soft"))
                        return 0;
-               if (softirq_verbose(this->class))
+               if (softirq_verbose(hlock_class(this)))
                        ret = 2;
                break;
        case LOCK_ENABLED_HARDIRQS:
                                   LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
                        return 0;
 #endif
-               if (hardirq_verbose(this->class))
+               if (hardirq_verbose(hlock_class(this)))
                        ret = 2;
                break;
        case LOCK_ENABLED_SOFTIRQS:
                                   LOCK_USED_IN_SOFTIRQ_READ, "soft-read"))
                        return 0;
 #endif
-               if (softirq_verbose(this->class))
+               if (softirq_verbose(hlock_class(this)))
                        ret = 2;
                break;
        case LOCK_ENABLED_HARDIRQS_READ:
                                           LOCK_USED_IN_HARDIRQ, "hard"))
                        return 0;
 #endif
-               if (hardirq_verbose(this->class))
+               if (hardirq_verbose(hlock_class(this)))
                        ret = 2;
                break;
        case LOCK_ENABLED_SOFTIRQS_READ:
                                           LOCK_USED_IN_SOFTIRQ, "soft"))
                        return 0;
 #endif
-               if (softirq_verbose(this->class))
+               if (softirq_verbose(hlock_class(this)))
                        ret = 2;
                break;
        default:
         * If already set then do not dirty the cacheline,
         * nor do any checks:
         */
-       if (likely(this->class->usage_mask & new_mask))
+       if (likely(hlock_class(this)->usage_mask & new_mask))
                return 1;
 
        if (!graph_lock())
        /*
         * Make sure we didnt race:
         */
-       if (unlikely(this->class->usage_mask & new_mask)) {
+       if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
                graph_unlock();
                return 1;
        }
 
-       this->class->usage_mask |= new_mask;
+       hlock_class(this)->usage_mask |= new_mask;
 
-       if (!save_trace(this->class->usage_traces + new_bit))
+       if (!save_trace(hlock_class(this)->usage_traces + new_bit))
                return 0;
 
        switch (new_bit) {
                return 0;
 
        hlock = curr->held_locks + depth;
-
-       hlock->class = class;
+       if (DEBUG_LOCKS_WARN_ON(!class))
+               return 0;
+       hlock->class_idx = class - lock_classes + 1;
        hlock->acquire_ip = ip;
        hlock->instance = lock;
        hlock->trylock = trylock;
 
 found_it:
        class = register_lock_class(lock, subclass, 0);
-       hlock->class = class;
+       hlock->class_idx = class - lock_classes + 1;
 
        curr->lockdep_depth = i;
        curr->curr_chain_key = hlock->prev_chain_key;
        for (; i < depth; i++) {
                hlock = curr->held_locks + i;
                if (!__lock_acquire(hlock->instance,
-                       hlock->class->subclass, hlock->trylock,
+                       hlock_class(hlock)->subclass, hlock->trylock,
                                hlock->read, hlock->check, hlock->hardirqs_off,
                                hlock->acquire_ip))
                        return 0;
        for (i++; i < depth; i++) {
                hlock = curr->held_locks + i;
                if (!__lock_acquire(hlock->instance,
-                       hlock->class->subclass, hlock->trylock,
+                       hlock_class(hlock)->subclass, hlock->trylock,
                                hlock->read, hlock->check, hlock->hardirqs_off,
                                hlock->acquire_ip))
                        return 0;
 
 #ifdef CONFIG_DEBUG_LOCKDEP
        hlock->prev_chain_key = 0;
-       hlock->class = NULL;
+       hlock->class_idx = 0;
        hlock->acquire_ip = 0;
        hlock->irq_context = 0;
 #endif
 found_it:
        hlock->waittime_stamp = sched_clock();
 
-       point = lock_contention_point(hlock->class, ip);
+       point = lock_contention_point(hlock_class(hlock), ip);
 
-       stats = get_lock_stats(hlock->class);
+       stats = get_lock_stats(hlock_class(hlock));
        if (point < ARRAY_SIZE(stats->contention_point))
                stats->contention_point[i]++;
        if (lock->cpu != smp_processor_id())
                hlock->holdtime_stamp = now;
        }
 
-       stats = get_lock_stats(hlock->class);
+       stats = get_lock_stats(hlock_class(hlock));
        if (waittime) {
                if (hlock->read)
                        lock_time_inc(&stats->read_waittime, waittime);