drm/i915: Fix preallocated barrier list append

					    struct intel_engine_cs *engine)

{

	intel_engine_mask_t tmp, mask = engine->mask;

	struct llist_node *pos = NULL, *next;

	struct llist_node *first = NULL, *last = NULL;

	struct intel_gt *gt = engine->gt;

	int err;

	 */

	for_each_engine_masked(engine, gt, mask, tmp) {

		u64 idx = engine->kernel_context->timeline->fence_context;

		struct llist_node *prev = first;

		struct active_node *node;

		node = reuse_idle_barrier(ref, idx);

		GEM_BUG_ON(rcu_access_pointer(node->base.fence) != ERR_PTR(-EAGAIN));

		GEM_BUG_ON(barrier_to_engine(node) != engine);

		next = barrier_to_ll(node);

		next->next = pos;

		if (!pos)

			pos = next;

		first = barrier_to_ll(node);

		first->next = prev;

		if (!last)

			last = first;

		intel_engine_pm_get(engine);

	}

	GEM_BUG_ON(!llist_empty(&ref->preallocated_barriers));

	llist_add_batch(next, pos, &ref->preallocated_barriers);

	llist_add_batch(first, last, &ref->preallocated_barriers);

	return 0;

unwind:

	while (pos) {

		struct active_node *node = barrier_from_ll(pos);

	while (first) {

		struct active_node *node = barrier_from_ll(first);

		pos = pos->next;

		first = first->next;

		atomic_dec(&ref->count);

		intel_engine_pm_put(barrier_to_engine(node));