[PATCH] nvme: add 'iopolicy' module parameter

[Hannes Reinecke <hare@suse.de>]

While the 'iopolicy' sysfs attribute can be set at runtime, most
storage arrays prefer to use the 'round-robin' iopolicy per default.
We can use udev rules to set this, but is getting rather unwieldy
for rebranded arrays as we would have to update the udev rules
anytime a new array shows up, leading to the same mess we currently
have in multipathd for configuring the RDAC arrays.

Hence this patch adds a module parameter 'iopolicy' to allow the
admin to switch the default, and to do away with the need for a
udev rule here.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/nvme/host/core.c      |  4 +---
 drivers/nvme/host/multipath.c | 10 ++++++++++
 drivers/nvme/host/nvme.h      |  4 ++++
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 58f5e8f454e2..282459a163e0 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2782,9 +2782,7 @@ static struct nvme_subsystem *nvme_init_subsystem(struct nvme_ctrl *ctrl,
 		kfree(subsys);
 		return ERR_PTR(-EINVAL);
 	}
-#ifdef CONFIG_NVME_MULTIPATH
-	subsys->iopolicy = NVME_IOPOLICY_NUMA;
-#endif
+	nvme_mpath_default_iopolicy(subsys);
 
 	subsys->dev.class = nvme_subsys_class;
 	subsys->dev.release = nvme_release_subsystem;
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 63367a717805..8f4eea978af7 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -13,6 +13,16 @@ module_param(multipath, bool, 0444);
 MODULE_PARM_DESC(multipath,
 	"turn on native support for multiple controllers per subsystem");
 
+static int iopolicy = NVME_IOPOLICY_NUMA;
+module_param(iopolicy, int, 0444);
+MODULE_PARM_DESC(iopolicy,
+	"Default multipath I/O policy; 0 - NUMA (default), 1 - Round-robin");
+
+void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys)
+{
+	subsys->iopolicy = iopolicy;
+}
+
 void nvme_mpath_unfreeze(struct nvme_subsystem *subsys)
 {
 	struct nvme_ns_head *h;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 6c786ea4185b..ac158b8e825d 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -771,6 +771,7 @@ static inline bool nvme_ctrl_use_ana(struct nvme_ctrl *ctrl)
 void nvme_mpath_unfreeze(struct nvme_subsystem *subsys);
 void nvme_mpath_wait_freeze(struct nvme_subsystem *subsys);
 void nvme_mpath_start_freeze(struct nvme_subsystem *subsys);
+void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys);
 bool nvme_mpath_set_disk_name(struct nvme_ns *ns, char *disk_name, int *flags);
 void nvme_failover_req(struct request *req);
 void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl);
@@ -869,6 +870,9 @@ static inline void nvme_mpath_wait_freeze(struct nvme_subsystem *subsys)
 static inline void nvme_mpath_start_freeze(struct nvme_subsystem *subsys)
 {
 }
+static inline void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys)
+{
+}
 #endif /* CONFIG_NVME_MULTIPATH */
 
 int nvme_revalidate_zones(struct nvme_ns *ns);
-- 
2.29.2