static int snapshot_ctr()

in dm-snap.c [1252:1442]

• 155 lines of code
• 23 McCabe index (conditional complexity)

static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
	struct dm_snapshot *s;
	struct dm_arg_set as;
	int i;
	int r = -EINVAL;
	char *origin_path, *cow_path;
	dev_t origin_dev, cow_dev;
	unsigned args_used, num_flush_bios = 1;
	fmode_t origin_mode = FMODE_READ;

	if (argc < 4) {
		ti->error = "requires 4 or more arguments";
		r = -EINVAL;
		goto bad;
	}

	if (dm_target_is_snapshot_merge(ti)) {
		num_flush_bios = 2;
		origin_mode = FMODE_WRITE;
	}

	s = kzalloc(sizeof(*s), GFP_KERNEL);
	if (!s) {
		ti->error = "Cannot allocate private snapshot structure";
		r = -ENOMEM;
		goto bad;
	}

	as.argc = argc;
	as.argv = argv;
	dm_consume_args(&as, 4);
	r = parse_snapshot_features(&as, s, ti);
	if (r)
		goto bad_features;

	origin_path = argv[0];
	argv++;
	argc--;

	r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
	if (r) {
		ti->error = "Cannot get origin device";
		goto bad_origin;
	}
	origin_dev = s->origin->bdev->bd_dev;

	cow_path = argv[0];
	argv++;
	argc--;

	cow_dev = dm_get_dev_t(cow_path);
	if (cow_dev && cow_dev == origin_dev) {
		ti->error = "COW device cannot be the same as origin device";
		r = -EINVAL;
		goto bad_cow;
	}

	r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
	if (r) {
		ti->error = "Cannot get COW device";
		goto bad_cow;
	}

	r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
	if (r) {
		ti->error = "Couldn't create exception store";
		r = -EINVAL;
		goto bad_store;
	}

	argv += args_used;
	argc -= args_used;

	s->ti = ti;
	s->valid = 1;
	s->snapshot_overflowed = 0;
	s->active = 0;
	atomic_set(&s->pending_exceptions_count, 0);
	spin_lock_init(&s->pe_allocation_lock);
	s->exception_start_sequence = 0;
	s->exception_complete_sequence = 0;
	s->out_of_order_tree = RB_ROOT;
	init_rwsem(&s->lock);
	INIT_LIST_HEAD(&s->list);
	spin_lock_init(&s->pe_lock);
	s->state_bits = 0;
	s->merge_failed = false;
	s->first_merging_chunk = 0;
	s->num_merging_chunks = 0;
	bio_list_init(&s->bios_queued_during_merge);
	bio_init(&s->flush_bio, NULL, 0);

	/* Allocate hash table for COW data */
	if (init_hash_tables(s)) {
		ti->error = "Unable to allocate hash table space";
		r = -ENOMEM;
		goto bad_hash_tables;
	}

	init_waitqueue_head(&s->in_progress_wait);

	s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
	if (IS_ERR(s->kcopyd_client)) {
		r = PTR_ERR(s->kcopyd_client);
		ti->error = "Could not create kcopyd client";
		goto bad_kcopyd;
	}

	r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);
	if (r) {
		ti->error = "Could not allocate mempool for pending exceptions";
		goto bad_pending_pool;
	}

	for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
		INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);

	spin_lock_init(&s->tracked_chunk_lock);

	ti->private = s;
	ti->num_flush_bios = num_flush_bios;
	if (s->discard_zeroes_cow)
		ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1);
	ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);

	/* Add snapshot to the list of snapshots for this origin */
	/* Exceptions aren't triggered till snapshot_resume() is called */
	r = register_snapshot(s);
	if (r == -ENOMEM) {
		ti->error = "Snapshot origin struct allocation failed";
		goto bad_load_and_register;
	} else if (r < 0) {
		/* invalid handover, register_snapshot has set ti->error */
		goto bad_load_and_register;
	}

	/*
	 * Metadata must only be loaded into one table at once, so skip this
	 * if metadata will be handed over during resume.
	 * Chunk size will be set during the handover - set it to zero to
	 * ensure it's ignored.
	 */
	if (r > 0) {
		s->store->chunk_size = 0;
		return 0;
	}

	r = s->store->type->read_metadata(s->store, dm_add_exception,
					  (void *)s);
	if (r < 0) {
		ti->error = "Failed to read snapshot metadata";
		goto bad_read_metadata;
	} else if (r > 0) {
		s->valid = 0;
		DMWARN("Snapshot is marked invalid.");
	}

	if (!s->store->chunk_size) {
		ti->error = "Chunk size not set";
		r = -EINVAL;
		goto bad_read_metadata;
	}

	r = dm_set_target_max_io_len(ti, s->store->chunk_size);
	if (r)
		goto bad_read_metadata;

	return 0;

bad_read_metadata:
	unregister_snapshot(s);
bad_load_and_register:
	mempool_exit(&s->pending_pool);
bad_pending_pool:
	dm_kcopyd_client_destroy(s->kcopyd_client);
bad_kcopyd:
	dm_exception_table_exit(&s->pending, pending_cache);
	dm_exception_table_exit(&s->complete, exception_cache);
bad_hash_tables:
	dm_exception_store_destroy(s->store);
bad_store:
	dm_put_device(ti, s->cow);
bad_cow:
	dm_put_device(ti, s->origin);
bad_origin:
bad_features:
	kfree(s);
bad:
	return r;
}