[PATCH] NVMe: Expose namespace unique identifier to sysfs
Matthew Wilcox
willy at linux.intel.com
Tue Dec 8 10:53:25 PST 2015
On Tue, Dec 08, 2015 at 10:26:45AM -0700, Keith Busch wrote:
> A controller namespace supporting 1.1 or 1.2 capabilities uniquely
> identifies itself with either the 64-bit EUI or 128-bit NGUID.
>
> This patch determines which the device supports and reports the unique
> identifier in new sysfs binary attribute "uuid". The attribute group is
> added to the gendisk's kobject directory.
I don't understand why we want to produce a binary attribute here instead
of a text attribute? We already have nicely-formatted UUIDs in sysfs
(see the %pU specifier to printk)
I don't think we should have one attribute that might be an eui64 or might
be a uuid. Maybe we should produce either an eui64 or a uuid attribute,
depending on which one the device reports?
> + if (ns->ctrl->vs >= NVME_VS(1, 1)) {
> + u8 *identifier = id->eui64;
> + int len = sizeof(id->eui64);
> +
> + if (bitmap_empty((void *)identifier, len * 8) &&
> + ns->ctrl->vs >= NVME_VS(1, 2)) {
> + identifier = id->nguid;
> + len = sizeof(id->nguid);
> + }
I'm a bit reluctant to use bitmap_empty here, because it's not actually
a bitmap. We almost want the inverse of memchr ("find me the first
byte that is non-zero"). Maybe somebody else knows a better functoin
to call here?
> + add_disk(ns->disk);
> + if (sysfs_create_group(&disk_to_dev(ns->disk)->kobj,
> + &nvme_ns_attrs_group)) {
> + del_gendisk(ns->disk);
> + nvme_put_ctrl(ctrl);
> + goto out_free_queue;
> + }
> return;
> out_free_disk:
> kfree(disk);
An interesting philosophical point ... if creating the group fails,
should we really refuse to use the namespace? It seems to me that we
can use it just fine.
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