dm-cache-target.c

	req.err = 0;
	init_waitqueue_head(&req.result_wait);

	spin_lock(&cache->invalidation_lock);
	list_add(&req.list, &cache->invalidation_requests);
	spin_unlock(&cache->invalidation_lock);
	wake_worker(cache);

	wait_event(req.result_wait, atomic_read(&req.complete));
	return req.err;
}

static int process_invalidate_cblocks_message(struct cache *cache, unsigned count,
					      const char **cblock_ranges)
{
	int r = 0;
	unsigned i;
	struct cblock_range range;

	if (!passthrough_mode(&cache->features)) {
		DMERR("cache has to be in passthrough mode for invalidation");
		return -EPERM;
	}

	for (i = 0; i < count; i++) {
		r = parse_cblock_range(cache, cblock_ranges[i], &range);
		if (r)
			break;

		r = validate_cblock_range(cache, &range);
		if (r)
			break;

		/*
		 * Pass begin and end origin blocks to the worker and wake it.
		 */
		r = request_invalidation(cache, &range);
		if (r)
			break;
	}

	return r;
}

/*
 * Supports
 *	"<key> <value>"
 * and
 *     "invalidate_cblocks [(<begin>)|(<begin>-<end>)]*
 *
 * The key migration_threshold is supported by the cache target core.
 */
static int cache_message(struct dm_target *ti, unsigned argc, char **argv)
{
	struct cache *cache = ti->private;

	if (!argc)
		return -EINVAL;

	if (!strcmp(argv[0], "invalidate_cblocks"))
		return process_invalidate_cblocks_message(cache, argc - 1, (const char **) argv + 1);

	if (argc != 2)
		return -EINVAL;

	return set_config_value(cache, argv[0], argv[1]);
}

static int cache_iterate_devices(struct dm_target *ti,
				 iterate_devices_callout_fn fn, void *data)
{
	int r = 0;
	struct cache *cache = ti->private;

	r = fn(ti, cache->cache_dev, 0, get_dev_size(cache->cache_dev), data);
	if (!r)
		r = fn(ti, cache->origin_dev, 0, ti->len, data);

	return r;
}

/*
 * We assume I/O is going to the origin (which is the volume
 * more likely to have restrictions e.g. by being striped).
 * (Looking up the exact location of the data would be expensive
 * and could always be out of date by the time the bio is submitted.)
 */
static int cache_bvec_merge(struct dm_target *ti,
			    struct bvec_merge_data *bvm,
			    struct bio_vec *biovec, int max_size)
{
	struct cache *cache = ti->private;
	struct request_queue *q = bdev_get_queue(cache->origin_dev->bdev);

	if (!q->merge_bvec_fn)
		return max_size;

	bvm->bi_bdev = cache->origin_dev->bdev;
	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}

static void set_discard_limits(struct cache *cache, struct queue_limits *limits)
{
	/*
	 * FIXME: these limits may be incompatible with the cache device
	 */
	limits->max_discard_sectors = cache->discard_block_size * 1024;
	limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;
}

static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
	struct cache *cache = ti->private;
	uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;

	/*
	 * If the system-determined stacked limits are compatible with the
	 * cache's blocksize (io_opt is a factor) do not override them.
	 */
	if (io_opt_sectors < cache->sectors_per_block ||
	    do_div(io_opt_sectors, cache->sectors_per_block)) {
		blk_limits_io_min(limits, 0);
		blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT);
	}
	set_discard_limits(cache, limits);
}

/*----------------------------------------------------------------*/

static struct target_type cache_target = {
	.name = "cache",
	.version = {1, 2, 0},
	.module = THIS_MODULE,
	.ctr = cache_ctr,
	.dtr = cache_dtr,
	.map = cache_map,
	.end_io = cache_end_io,
	.postsuspend = cache_postsuspend,
	.preresume = cache_preresume,
	.resume = cache_resume,
	.status = cache_status,
	.message = cache_message,
	.iterate_devices = cache_iterate_devices,
	.merge = cache_bvec_merge,
	.io_hints = cache_io_hints,
};

static int __init dm_cache_init(void)
{
	int r;

	r = dm_register_target(&cache_target);
	if (r) {
		DMERR("cache target registration failed: %d", r);
		return r;
	}

	migration_cache = KMEM_CACHE(dm_cache_migration, 0);
	if (!migration_cache) {
		dm_unregister_target(&cache_target);
		return -ENOMEM;
	}

	return 0;
}

static void __exit dm_cache_exit(void)
{
	dm_unregister_target(&cache_target);
	kmem_cache_destroy(migration_cache);
}

module_init(dm_cache_init);
module_exit(dm_cache_exit);

MODULE_DESCRIPTION(DM_NAME " cache target");
MODULE_AUTHOR("Joe Thornber <ejt@redhat.com>");
MODULE_LICENSE("GPL");