nvme-fabrics: only reserve a single tag

Fabrics drivers currently reserve two tags on the admin queue.  But
given that the connect command is only run on a freshly created queue
or after all commands have been force aborted we only need to reserve
a single tag.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Daniel Wagner <dwagner@suse.de>

drivers/nvme/host/fabrics.h

@@ -18,6 +18,13 @@
 /* default is -1: the fail fast mechanism is disabled  */
 #define NVMF_DEF_FAIL_FAST_TMO		-1
 
+/*
+ * Reserved one command for internal usage.  This command is used for sending
+ * the connect command, as well as for the keep alive command on the admin
+ * queue once live.
+ */
+#define NVMF_RESERVED_TAGS	1
+
 /*
  * Define a host as seen by the target.  We allocate one at boot, but also
  * allow the override it when creating controllers.  This is both to provide

drivers/nvme/host/fc.c

@@ -2863,7 +2863,7 @@ nvme_fc_create_io_queues(struct nvme_fc_ctrl *ctrl)
 	memset(&ctrl->tag_set, 0, sizeof(ctrl->tag_set));
 	ctrl->tag_set.ops = &nvme_fc_mq_ops;
 	ctrl->tag_set.queue_depth = ctrl->ctrl.opts->queue_size;
-	ctrl->tag_set.reserved_tags = 1; /* fabric connect */
+	ctrl->tag_set.reserved_tags = NVMF_RESERVED_TAGS;
 	ctrl->tag_set.numa_node = ctrl->ctrl.numa_node;
 	ctrl->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	ctrl->tag_set.cmd_size =
@@ -3485,7 +3485,7 @@ nvme_fc_init_ctrl(struct device *dev, struct nvmf_ctrl_options *opts,
 	memset(&ctrl->admin_tag_set, 0, sizeof(ctrl->admin_tag_set));
 	ctrl->admin_tag_set.ops = &nvme_fc_admin_mq_ops;
 	ctrl->admin_tag_set.queue_depth = NVME_AQ_MQ_TAG_DEPTH;
-	ctrl->admin_tag_set.reserved_tags = 2; /* fabric connect + Keep-Alive */
+	ctrl->admin_tag_set.reserved_tags = NVMF_RESERVED_TAGS;
 	ctrl->admin_tag_set.numa_node = ctrl->ctrl.numa_node;
 	ctrl->admin_tag_set.cmd_size =
 		struct_size((struct nvme_fcp_op_w_sgl *)NULL, priv,

drivers/nvme/host/rdma.c

@@ -798,7 +798,7 @@ static struct blk_mq_tag_set *nvme_rdma_alloc_tagset(struct nvme_ctrl *nctrl,
 		memset(set, 0, sizeof(*set));
 		set->ops = &nvme_rdma_admin_mq_ops;
 		set->queue_depth = NVME_AQ_MQ_TAG_DEPTH;
-		set->reserved_tags = 2; /* connect + keep-alive */
+		set->reserved_tags = NVMF_RESERVED_TAGS;
 		set->numa_node = nctrl->numa_node;
 		set->cmd_size = sizeof(struct nvme_rdma_request) +
 				NVME_RDMA_DATA_SGL_SIZE;
@@ -811,7 +811,7 @@ static struct blk_mq_tag_set *nvme_rdma_alloc_tagset(struct nvme_ctrl *nctrl,
 		memset(set, 0, sizeof(*set));
 		set->ops = &nvme_rdma_mq_ops;
 		set->queue_depth = nctrl->sqsize + 1;
-		set->reserved_tags = 1; /* fabric connect */
+		set->reserved_tags = NVMF_RESERVED_TAGS;
 		set->numa_node = nctrl->numa_node;
 		set->flags = BLK_MQ_F_SHOULD_MERGE;
 		set->cmd_size = sizeof(struct nvme_rdma_request) +

drivers/nvme/host/tcp.c

@@ -1575,7 +1575,7 @@ static struct blk_mq_tag_set *nvme_tcp_alloc_tagset(struct nvme_ctrl *nctrl,
 		memset(set, 0, sizeof(*set));
 		set->ops = &nvme_tcp_admin_mq_ops;
 		set->queue_depth = NVME_AQ_MQ_TAG_DEPTH;
-		set->reserved_tags = 2; /* connect + keep-alive */
+		set->reserved_tags = NVMF_RESERVED_TAGS;
 		set->numa_node = nctrl->numa_node;
 		set->flags = BLK_MQ_F_BLOCKING;
 		set->cmd_size = sizeof(struct nvme_tcp_request);
@@ -1587,7 +1587,7 @@ static struct blk_mq_tag_set *nvme_tcp_alloc_tagset(struct nvme_ctrl *nctrl,
 		memset(set, 0, sizeof(*set));
 		set->ops = &nvme_tcp_mq_ops;
 		set->queue_depth = nctrl->sqsize + 1;
-		set->reserved_tags = 1; /* fabric connect */
+		set->reserved_tags = NVMF_RESERVED_TAGS;
 		set->numa_node = nctrl->numa_node;
 		set->flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_BLOCKING;
 		set->cmd_size = sizeof(struct nvme_tcp_request);

drivers/nvme/target/loop.c

@@ -349,7 +349,7 @@ static int nvme_loop_configure_admin_queue(struct nvme_loop_ctrl *ctrl)
 	memset(&ctrl->admin_tag_set, 0, sizeof(ctrl->admin_tag_set));
 	ctrl->admin_tag_set.ops = &nvme_loop_admin_mq_ops;
 	ctrl->admin_tag_set.queue_depth = NVME_AQ_MQ_TAG_DEPTH;
-	ctrl->admin_tag_set.reserved_tags = 2; /* connect + keep-alive */
+	ctrl->admin_tag_set.reserved_tags = NVMF_RESERVED_TAGS;
 	ctrl->admin_tag_set.numa_node = ctrl->ctrl.numa_node;
 	ctrl->admin_tag_set.cmd_size = sizeof(struct nvme_loop_iod) +
 		NVME_INLINE_SG_CNT * sizeof(struct scatterlist);
@@ -520,7 +520,7 @@ static int nvme_loop_create_io_queues(struct nvme_loop_ctrl *ctrl)
 	memset(&ctrl->tag_set, 0, sizeof(ctrl->tag_set));
 	ctrl->tag_set.ops = &nvme_loop_mq_ops;
 	ctrl->tag_set.queue_depth = ctrl->ctrl.opts->queue_size;
-	ctrl->tag_set.reserved_tags = 1; /* fabric connect */
+	ctrl->tag_set.reserved_tags = NVMF_RESERVED_TAGS;
 	ctrl->tag_set.numa_node = ctrl->ctrl.numa_node;
 	ctrl->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 	ctrl->tag_set.cmd_size = sizeof(struct nvme_loop_iod) +