[PATCH] nvme: make providing NGUID as UUID usage less scary

[AlanCui4080 <me@alancui.cc>]

Hi, 

> From: Keith Busch <kbusch@kernel.org>
> 
> The warning is a bit alarming, and it only prints for the very first
> non-sgl capable device that receives a passthrough command. Just log an
> informational message on initial discovery for every device.

Since we decide to show this warning at device initial discovery stage,
here are some similar warnings that I think are essentially the same.

grep -C3 -rn "dev_warn_once" ./drivers/nvme/*
```
./drivers/nvme/host/sysfs.c-147-         * we have no UUID set
./drivers/nvme/host/sysfs.c-148-         */
./drivers/nvme/host/sysfs.c-149-        if (uuid_is_null(&ids->uuid)) {
./drivers/nvme/host/sysfs.c:150:                dev_warn_once(dev,
./drivers/nvme/host/sysfs.c-151-                        "No UUID available providing old NGUID\n");
./drivers/nvme/host/sysfs.c-152-                return sysfs_emit(buf, "%pU\n", ids->nguid);
./drivers/nvme/host/sysfs.c-153-        }
```

This warning will only complain for the first partition of the first device also.
And for NVMe devices, according to the NVM-Express-1_4 specification p.175 Figure 251:
"Bit 9 (UUID List): ...", UUID is not mandatory i guess. So let's degrade it into a
informational message on initial discovery for every device.

Signed-off-by: Alan Cui <me@alancui.cc>
---
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 3fdcd73b9546..c432d8bc7b62 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4296,6 +4296,10 @@ static void nvme_validate_ns(struct nvme_ns *ns, struct nvme_ns_info *info)
                goto out;
        }
 
+       if (uuid_is_null(&info->ids.uuid)) {
+               dev_info(ns->ctrl->device, "No UUID available, uuid_show providing old NGUID\n");
+       }
+
        ret = nvme_update_ns_info(ns, info);
 out:
        /*
diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
index 29430949ce2f..839a36c22ebf 100644
--- a/drivers/nvme/host/sysfs.c
+++ b/drivers/nvme/host/sysfs.c
@@ -147,8 +147,6 @@ static ssize_t uuid_show(struct device *dev, struct device_attribute *attr,
         * we have no UUID set
         */
        if (uuid_is_null(&ids->uuid)) {
-               dev_warn_once(dev,
-                       "No UUID available providing old NGUID\n");
                return sysfs_emit(buf, "%pU\n", ids->nguid);
        }
        return sysfs_emit(buf, "%pU\n", &ids->uuid);

--
2.54.0