static struct mapped_device *alloc_dev(int minor)
{
	int r, numa_node_id = dm_get_numa_node();
	struct dax_device *dax_dev;
	struct mapped_device *md;
	void *old_md;

	md = kvzalloc_node(sizeof(*md), GFP_KERNEL, numa_node_id);
	if (!md) {
		DMWARN("unable to allocate device, out of memory.");
		return NULL;
	}

	if (!try_module_get(THIS_MODULE))
		goto bad_module_get;

	/* get a minor number for the dev */
	if (minor == DM_ANY_MINOR)
		r = next_free_minor(&minor);
	else
		r = specific_minor(minor);
	if (r < 0)
		goto bad_minor;

	r = init_srcu_struct(&md->io_barrier);
	if (r < 0)
		goto bad_io_barrier;

	md->numa_node_id = numa_node_id;
	md->use_blk_mq = dm_use_blk_mq_default();
	md->init_tio_pdu = false;
	md->type = DM_TYPE_NONE;
	mutex_init(&md->suspend_lock);
	mutex_init(&md->type_lock);
	mutex_init(&md->table_devices_lock);
	spin_lock_init(&md->deferred_lock);
	atomic_set(&md->holders, 1);
	atomic_set(&md->open_count, 0);
	atomic_set(&md->event_nr, 0);
	atomic_set(&md->uevent_seq, 0);
	INIT_LIST_HEAD(&md->uevent_list);
	INIT_LIST_HEAD(&md->table_devices);
	spin_lock_init(&md->uevent_lock);

	md->queue = blk_alloc_queue_node(GFP_KERNEL, numa_node_id);
	if (!md->queue)
		goto bad;

	dm_init_md_queue(md);

	md->disk = alloc_disk_node(1, numa_node_id);
	if (!md->disk)
		goto bad;

	atomic_set(&md->pending[0], 0);
	atomic_set(&md->pending[1], 0);
	init_waitqueue_head(&md->wait);
	INIT_WORK(&md->work, dm_wq_work);
	init_waitqueue_head(&md->eventq);
	init_completion(&md->kobj_holder.completion);
	md->kworker_task = NULL;

	md->disk->major = _major;
	md->disk->first_minor = minor;
	md->disk->fops = &dm_blk_dops;
	md->disk->queue = md->queue;
	md->disk->private_data = md;
	sprintf(md->disk->disk_name, "dm-%d", minor);

	dax_dev = alloc_dax(md, md->disk->disk_name, &dm_dax_ops);
	if (!dax_dev)
		goto bad;
	md->dax_dev = dax_dev;

	add_disk(md->disk);
	format_dev_t(md->name, MKDEV(_major, minor));

	md->wq = alloc_workqueue("kdmflush", WQ_MEM_RECLAIM, 0);
	if (!md->wq)
		goto bad;

	md->bdev = bdget_disk(md->disk, 0);
	if (!md->bdev)
		goto bad;

	bio_init(&md->flush_bio, NULL, 0);
	bio_set_dev(&md->flush_bio, md->bdev);
	md->flush_bio.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC;

	dm_stats_init(&md->stats);

	/* Populate the mapping, nobody knows we exist yet */
	spin_lock(&_minor_lock);
	old_md = idr_replace(&_minor_idr, md, minor);
	spin_unlock(&_minor_lock);

	BUG_ON(old_md != MINOR_ALLOCED);

	return md;

bad:
	cleanup_mapped_device(md);
bad_io_barrier:
	free_minor(minor);
bad_minor:
	module_put(THIS_MODULE);
bad_module_get:
	kvfree(md);
	return NULL;
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.