- old_head = device->pending_bios;
- device->pending_bios = pending;
- if (device->pending_bio_tail)
- tail->bi_next = old_head;
- else
- device->pending_bio_tail = tail;
- device->running_pending = 0;
+ /*
+ * the main goal here is that we don't want to
+ * block if we're going to be able to submit
+ * more requests without blocking.
+ *
+ * This code does two great things, it pokes into
+ * the elevator code from a filesystem _and_
+ * it makes assumptions about how batching works.
+ */
+ if (ioc && ioc->nr_batch_requests > 0 &&
+ time_before(jiffies, ioc->last_waited + HZ/50UL) &&
+ (last_waited == 0 ||
+ ioc->last_waited == last_waited)) {
+ /*
+ * we want to go through our batch of
+ * requests and stop. So, we copy out
+ * the ioc->last_waited time and test
+ * against it before looping
+ */
+ last_waited = ioc->last_waited;
+ if (need_resched()) {
+ if (num_sync_run) {
+ blk_run_backing_dev(bdi, NULL);
+ num_sync_run = 0;
+ }
+ cond_resched();
+ }
+ continue;
+ }
+ spin_lock(&device->io_lock);
+ requeue_list(pending_bios, pending, tail);
+ device->running_pending = 1;