[PATCH 1/2] nvmet-rdma: avoid circular locking dependency on install_queue()

[Hannes Reinecke]

nvmet_rdma_install_queue() is driven from the ->io_work workqueue
function, but will call flush_workqueue() which might trigger
->release_work() which in itself calls flush_work on ->io_work.

To avoid that move the check for any pending queue disconnects
to the 'install_queue()' callback. This replicates what the tcp
code is already doing, and also allows us to return a
'controller busy' connect response until all disconnects
are completed.

Signed-off-by: Hannes Reinecke <hare at suse.de>
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki at wdc.com>
---
 drivers/nvme/target/rdma.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index 4597bca43a6d..8e011bdec3b0 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -1582,11 +1582,6 @@ static int nvmet_rdma_queue_connect(struct rdma_cm_id *cm_id,
 		goto put_device;
 	}
 
-	if (queue->host_qid == 0) {
-		/* Let inflight controller teardown complete */
-		flush_workqueue(nvmet_wq);
-	}
-
 	ret = nvmet_rdma_cm_accept(cm_id, queue, &event->param.conn);
 	if (ret) {
 		/*
@@ -1975,6 +1970,24 @@ static void nvmet_rdma_remove_port(struct nvmet_port *nport)
 	kfree(port);
 }
 
+static u16 nvmet_rdma_install_queue(struct nvmet_sq *sq)
+{
+	if (sq->qid == 0) {
+		struct nvmet_rdma_queue *q;
+
+		mutex_lock(&nvmet_rdma_queue_mutex);
+		list_for_each_entry(q, &nvmet_rdma_queue_list, queue_list) {
+			if (q->state == NVMET_RDMA_Q_DISCONNECTING) {
+				mutex_unlock(&nvmet_rdma_queue_mutex);
+				/* Retry for pending controller teardown */
+				return NVME_SC_CONNECT_CTRL_BUSY;
+			}
+		}
+		mutex_unlock(&nvmet_rdma_queue_mutex);
+	}
+	return 0;
+}
+
 static void nvmet_rdma_disc_port_addr(struct nvmet_req *req,
 		struct nvmet_port *nport, char *traddr)
 {
@@ -2014,6 +2027,7 @@ static const struct nvmet_fabrics_ops nvmet_rdma_ops = {
 	.remove_port		= nvmet_rdma_remove_port,
 	.queue_response		= nvmet_rdma_queue_response,
 	.delete_ctrl		= nvmet_rdma_delete_ctrl,
+	.install_queue		= nvmet_rdma_install_queue,
 	.disc_traddr		= nvmet_rdma_disc_port_addr,
 	.get_mdts		= nvmet_rdma_get_mdts,
 	.get_max_queue_size	= nvmet_rdma_get_max_queue_size,
-- 
2.35.3