block: add block polling support

[cascardo/linux.git] / block / blk-core.c

diff --git a/block/blk-core.c b/block/blk-core.c
index e93df6d..fa36b4f 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3312,6 +3312,47 @@ void blk_finish_plug(struct blk_plug *plug)
 }
 EXPORT_SYMBOL(blk_finish_plug);
 
+bool blk_poll(struct request_queue *q, blk_qc_t cookie)
+{
+       struct blk_plug *plug;
+       long state;
+
+       if (!q->mq_ops || !q->mq_ops->poll || !blk_qc_t_valid(cookie) ||
+           !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
+               return false;
+
+       plug = current->plug;
+       if (plug)
+               blk_flush_plug_list(plug, false);
+
+       state = current->state;
+       while (!need_resched()) {
+               unsigned int queue_num = blk_qc_t_to_queue_num(cookie);
+               struct blk_mq_hw_ctx *hctx = q->queue_hw_ctx[queue_num];
+               int ret;
+
+               hctx->poll_invoked++;
+
+               ret = q->mq_ops->poll(hctx, blk_qc_t_to_tag(cookie));
+               if (ret > 0) {
+                       hctx->poll_success++;
+                       set_current_state(TASK_RUNNING);
+                       return true;
+               }
+
+               if (signal_pending_state(state, current))
+                       set_current_state(TASK_RUNNING);
+
+               if (current->state == TASK_RUNNING)
+                       return true;
+               if (ret < 0)
+                       break;
+               cpu_relax();
+       }
+
+       return false;
+}
+
 #ifdef CONFIG_PM
 /**
  * blk_pm_runtime_init - Block layer runtime PM initialization routine