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>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 6f0a58e7613d..6f9b7534928e 100644
--- 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;
 }