nvme: don't intialize hwmon for discovery controllers

Discovery controllers usually don't support smart log page command.
So when we connect to the discovery controller we see this warning:
nvme nvme0: Failed to read smart log (error 24577)
nvme nvme0: new ctrl: NQN "nqn.2014-08.org.nvmexpress.discovery", addr 192.168.123.1:8009
nvme nvme0: Removing ctrl: NQN "nqn.2014-08.org.nvmexpress.discovery"

Introduce a new helper to understand if the controller is a discovery
controller and use this helper to skip nvme_init_hwmon (also use it in
other places that we check if the controller is a discovery controller).

Fixes: 400b6a7 ("nvme: Add hardware monitoring support")
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Author: sagigrimberg

drivers/nvme/host/core.c

@@ -2856,6 +2856,11 @@ static const struct attribute_group *nvme_subsys_attrs_groups[] = {
 	NULL,
 };
 
+static inline bool nvme_discovery_ctrl(struct nvme_ctrl *ctrl)
+{
+	return ctrl->opts && ctrl->opts->discovery_nqn;
+}
+
 static bool nvme_validate_cntlid(struct nvme_subsystem *subsys,
 		struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
 {
@@ -2875,7 +2880,7 @@ static bool nvme_validate_cntlid(struct nvme_subsystem *subsys,
 		}
 
 		if ((id->cmic & NVME_CTRL_CMIC_MULTI_CTRL) ||
-		    (ctrl->opts && ctrl->opts->discovery_nqn))
+		    nvme_discovery_ctrl(ctrl))
 			continue;
 
 		dev_err(ctrl->device,
@@ -3144,7 +3149,7 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 			goto out_free;
 		}
 
-		if (!ctrl->opts->discovery_nqn && !ctrl->kas) {
+		if (!nvme_discovery_ctrl(ctrl) && !ctrl->kas) {
 			dev_err(ctrl->device,
 				"keep-alive support is mandatory for fabrics\n");
 			ret = -EINVAL;
@@ -3184,7 +3189,7 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
 	if (ret < 0)
 		return ret;
 
-	if (!ctrl->identified) {
+	if (!ctrl->identified && !nvme_discovery_ctrl(ctrl)) {
 		ret = nvme_hwmon_init(ctrl);
 		if (ret < 0)
 			return ret;