[PATCH] NVMe: Re-attach waitqueue following device reset

[Sam Bradshaw]

Bios queued to sq_cong prior to and during a device reset may not 
get re-issued or may get issued very slowly following the completion 
of the reset sequence.  The waitqueue was detached as part of the 
sequence and never re-attached, forcing all new make_request() bios 
to be queued and the queue to be flushed out without the help of the 
completion path waking the kthread.

This patch re-attaches the waitqueue as part of the reset process.

Signed-off-by: Sam Bradshaw <sbradshaw at micron.com>
---
diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
index b85a2a0..8133ee8 100644
--- a/drivers/block/nvme-core.c
+++ b/drivers/block/nvme-core.c
@@ -2329,6 +2329,23 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
 	nvme_free_queues(dev, nr_io_queues + 1);
 	nvme_assign_io_queues(dev);
 
+	/* Re-attach the waitqueue */
+	for (i = dev->queue_count - 1; i >= 1; i--) {
+		struct nvme_queue *nvmeq = raw_nvmeq(dev, i);
+
+		if (nvmeq) {
+			spin_lock_irq(&nvmeq->q_lock);
+			init_waitqueue_head(&nvmeq->sq_full);
+			init_waitqueue_entry(&nvmeq->sq_cong_wait,
+								nvme_thread);
+			if (bio_list_peek(&nvmeq->sq_cong) ||
+						!list_empty(&nvmeq->iod_bio))
+				add_wait_queue(&nvmeq->sq_full,
+							&nvmeq->sq_cong_wait);
+			spin_unlock_irq(&nvmeq->q_lock);
+		}
+	}
+
 	return 0;
 
  free_queues: