static int virtio_mem_memory_notifier_cb()

in virtio_mem.c [950:1079]

• 93 lines of code
• 24 McCabe index (conditional complexity)

static int virtio_mem_memory_notifier_cb(struct notifier_block *nb,
					 unsigned long action, void *arg)
{
	struct virtio_mem *vm = container_of(nb, struct virtio_mem,
					     memory_notifier);
	struct memory_notify *mhp = arg;
	const unsigned long start = PFN_PHYS(mhp->start_pfn);
	const unsigned long size = PFN_PHYS(mhp->nr_pages);
	int rc = NOTIFY_OK;
	unsigned long id;

	if (!virtio_mem_overlaps_range(vm, start, size))
		return NOTIFY_DONE;

	if (vm->in_sbm) {
		id = virtio_mem_phys_to_mb_id(start);
		/*
		 * In SBM, we add memory in separate memory blocks - we expect
		 * it to be onlined/offlined in the same granularity. Bail out
		 * if this ever changes.
		 */
		if (WARN_ON_ONCE(size != memory_block_size_bytes() ||
				 !IS_ALIGNED(start, memory_block_size_bytes())))
			return NOTIFY_BAD;
	} else {
		id = virtio_mem_phys_to_bb_id(vm, start);
		/*
		 * In BBM, we only care about onlining/offlining happening
		 * within a single big block, we don't care about the
		 * actual granularity as we don't track individual Linux
		 * memory blocks.
		 */
		if (WARN_ON_ONCE(id != virtio_mem_phys_to_bb_id(vm, start + size - 1)))
			return NOTIFY_BAD;
	}

	/*
	 * Avoid circular locking lockdep warnings. We lock the mutex
	 * e.g., in MEM_GOING_ONLINE and unlock it in MEM_ONLINE. The
	 * blocking_notifier_call_chain() has it's own lock, which gets unlocked
	 * between both notifier calls and will bail out. False positive.
	 */
	lockdep_off();

	switch (action) {
	case MEM_GOING_OFFLINE:
		mutex_lock(&vm->hotplug_mutex);
		if (vm->removing) {
			rc = notifier_from_errno(-EBUSY);
			mutex_unlock(&vm->hotplug_mutex);
			break;
		}
		vm->hotplug_active = true;
		if (vm->in_sbm)
			virtio_mem_sbm_notify_going_offline(vm, id);
		else
			virtio_mem_bbm_notify_going_offline(vm, id,
							    mhp->start_pfn,
							    mhp->nr_pages);
		break;
	case MEM_GOING_ONLINE:
		mutex_lock(&vm->hotplug_mutex);
		if (vm->removing) {
			rc = notifier_from_errno(-EBUSY);
			mutex_unlock(&vm->hotplug_mutex);
			break;
		}
		vm->hotplug_active = true;
		if (vm->in_sbm)
			rc = virtio_mem_sbm_notify_going_online(vm, id);
		break;
	case MEM_OFFLINE:
		if (vm->in_sbm)
			virtio_mem_sbm_notify_offline(vm, id);

		atomic64_add(size, &vm->offline_size);
		/*
		 * Trigger the workqueue. Now that we have some offline memory,
		 * maybe we can handle pending unplug requests.
		 */
		if (!unplug_online)
			virtio_mem_retry(vm);

		vm->hotplug_active = false;
		mutex_unlock(&vm->hotplug_mutex);
		break;
	case MEM_ONLINE:
		if (vm->in_sbm)
			virtio_mem_sbm_notify_online(vm, id, mhp->start_pfn);

		atomic64_sub(size, &vm->offline_size);
		/*
		 * Start adding more memory once we onlined half of our
		 * threshold. Don't trigger if it's possibly due to our actipn
		 * (e.g., us adding memory which gets onlined immediately from
		 * the core).
		 */
		if (!atomic_read(&vm->wq_active) &&
		    virtio_mem_could_add_memory(vm, vm->offline_threshold / 2))
			virtio_mem_retry(vm);

		vm->hotplug_active = false;
		mutex_unlock(&vm->hotplug_mutex);
		break;
	case MEM_CANCEL_OFFLINE:
		if (!vm->hotplug_active)
			break;
		if (vm->in_sbm)
			virtio_mem_sbm_notify_cancel_offline(vm, id);
		else
			virtio_mem_bbm_notify_cancel_offline(vm, id,
							     mhp->start_pfn,
							     mhp->nr_pages);
		vm->hotplug_active = false;
		mutex_unlock(&vm->hotplug_mutex);
		break;
	case MEM_CANCEL_ONLINE:
		if (!vm->hotplug_active)
			break;
		vm->hotplug_active = false;
		mutex_unlock(&vm->hotplug_mutex);
		break;
	default:
		break;
	}

	lockdep_on();

	return rc;
}