null_blk: restart request processing on completion handler

When irqmode=2 (IRQ completion handler is timer) and queue_mode=1
(Block interface to use is rq), the completion handler should restart
request handling for any pending requests on a queue because request
processing stops when the number of commands are queued more than
hw_queue_depth (null_rq_prep_fn returns BLKPREP_DEFER).

Without this change, the following command cannot finish.

	# modprobe null_blk irqmode=2 queue_mode=1 hw_queue_depth=1
	# fio --name=t --rw=read --size=1g --direct=1 \
	  --ioengine=libaio --iodepth=64 --filename=/dev/nullb0

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 6f0a58e7613db5e499e70c7b5f7ffec804d429bf..6f9b7534928e2a8db2d35732d6e3511a1c4455bc 100644 (file)
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -243,6 +243,17 @@ static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
                        cmd = container_of(entry, struct nullb_cmd, ll_list);
                        entry = entry->next;
                        end_cmd(cmd);
+
+                       if (cmd->rq) {
+                               struct request_queue *q = cmd->rq->q;
+
+                               if (!q->mq_ops && blk_queue_stopped(q)) {
+                                       spin_lock(q->queue_lock);
+                                       if (blk_queue_stopped(q))
+                                               blk_start_queue(q);
+                                       spin_unlock(q->queue_lock);
+                               }
+                       }
                } while (entry);
        }
 
@@ -334,6 +345,7 @@ static int null_rq_prep_fn(struct request_queue *q, struct request *req)
                req->special = cmd;
                return BLKPREP_OK;
        }
+       blk_stop_queue(q);
 
        return BLKPREP_DEFER;
 }