nvmet-rdma: avoid circular locking dependency on install_queue()

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 check for pending queue in disconnecting status,
and return 'controller busy' when we reached a certain threshold.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>

diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index 4597bca43a6d87269f557dfa3b35d47da8031ff1..667f9c04f35d538bb361f733e50c62bb7c52d9c3 100644 (file)
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -37,6 +37,8 @@
 #define NVMET_RDMA_MAX_MDTS                    8
 #define NVMET_RDMA_MAX_METADATA_MDTS           5
 
+#define NVMET_RDMA_BACKLOG 128
+
 struct nvmet_rdma_srq;
 
 struct nvmet_rdma_cmd {
@@ -1583,8 +1585,19 @@ static int nvmet_rdma_queue_connect(struct rdma_cm_id *cm_id,
        }
 
        if (queue->host_qid == 0) {
-               /* Let inflight controller teardown complete */
-               flush_workqueue(nvmet_wq);
+               struct nvmet_rdma_queue *q;
+               int pending = 0;
+
+               /* Check for pending controller teardown */
+               mutex_lock(&nvmet_rdma_queue_mutex);
+               list_for_each_entry(q, &nvmet_rdma_queue_list, queue_list) {
+                       if (q->nvme_sq.ctrl == queue->nvme_sq.ctrl &&
+                           q->state == NVMET_RDMA_Q_DISCONNECTING)
+                               pending++;
+               }
+               mutex_unlock(&nvmet_rdma_queue_mutex);
+               if (pending > NVMET_RDMA_BACKLOG)
+                       return NVME_SC_CONNECT_CTRL_BUSY;
        }
 
        ret = nvmet_rdma_cm_accept(cm_id, queue, &event->param.conn);
@@ -1880,7 +1893,7 @@ static int nvmet_rdma_enable_port(struct nvmet_rdma_port *port)
                goto out_destroy_id;
        }
 
-       ret = rdma_listen(cm_id, 128);
+       ret = rdma_listen(cm_id, NVMET_RDMA_BACKLOG);
        if (ret) {
                pr_err("listening to %pISpcs failed (%d)\n", addr, ret);
                goto out_destroy_id;