[PATCH v6 08/10] nvme: provide UUID value to userspace

[Johannes Thumshirn]

Now that we have a way for getting the UUID from a target, provide it
to userspace as well.

Unfortunately there is already a sysfs attribute called UUID which is
a misnomer as it holds the NGUID value. So instead of creating yet
another wrong name, create a new 'nguid' sysfs attribute for the
NGUID. For the UUID attribute add a check wheter the namespace has a
UUID assigned to it and return this or return the NGUID to maintain
backwards compatibility. This should give userspace a chance to catch
up.

Signed-off-by: Johannes Thumshirn <jthumsh...@suse.de>
Reviewed-by: Christoph Hellwig <h...@lst.de>
Reviewed-by: Hannes Reinecke <h...@suse.com>
Reviewed-by: Sagi Grimberg <s...@rimberg.me>
---
 drivers/nvme/host/core.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 34857191c8bd..462187a4047b 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1879,11 +1879,28 @@ static ssize_t wwid_show(struct device *dev, struct 
device_attribute *attr,
 }
 static DEVICE_ATTR(wwid, S_IRUGO, wwid_show, NULL);
 
+static ssize_t nguid_show(struct device *dev, struct device_attribute *attr,
+                         char *buf)
+{
+       struct nvme_ns *ns = nvme_get_ns_from_dev(dev);
+       return sprintf(buf, "%pU\n", ns->nguid);
+}
+static DEVICE_ATTR(nguid, S_IRUGO, nguid_show, NULL);
+
 static ssize_t uuid_show(struct device *dev, struct device_attribute *attr,
                                                                char *buf)
 {
        struct nvme_ns *ns = nvme_get_ns_from_dev(dev);
-       return sprintf(buf, "%pU\n", ns->nguid);
+
+       /* For backward compatibility expose the NGUID to userspace if
+        * we have no UUID set
+        */
+       if (!memchr_inv(ns->uuid, 0, sizeof(ns->uuid))) {
+               printk_ratelimited(KERN_WARNING
+                                  "No UUID available providing old NGUID\n");
+               return sprintf(buf, "%pU\n", ns->nguid);
+       }
+       return sprintf(buf, "%pU\n", ns->uuid);
 }
 static DEVICE_ATTR(uuid, S_IRUGO, uuid_show, NULL);
 
@@ -1906,6 +1923,7 @@ static DEVICE_ATTR(nsid, S_IRUGO, nsid_show, NULL);
 static struct attribute *nvme_ns_attrs[] = {
        &dev_attr_wwid.attr,
        &dev_attr_uuid.attr,
+       &dev_attr_nguid.attr,
        &dev_attr_eui.attr,
        &dev_attr_nsid.attr,
        NULL,
@@ -1918,6 +1936,11 @@ static umode_t nvme_ns_attrs_are_visible(struct kobject 
*kobj,
        struct nvme_ns *ns = nvme_get_ns_from_dev(dev);
 
        if (a == &dev_attr_uuid.attr) {
+               if (!memchr_inv(ns->uuid, 0, sizeof(ns->uuid)) ||
+                   !memchr_inv(ns->nguid, 0, sizeof(ns->nguid)))
+                       return 0;
+       }
+       if (a == &dev_attr_nguid.attr) {
                if (!memchr_inv(ns->nguid, 0, sizeof(ns->nguid)))
                        return 0;
        }
-- 
2.12.3