On Wed, 2015-04-29 at 11:59 -0700, Dan Williams wrote:
On Wed, Apr 29, 2015 at 11:25 AM, Toshi Kani
> Hi Dan,
> Thanks for the update. This version of the patchset enumerates our NFIT
> table properly. :-)
> On Tue, 2015-04-28 at 14:25 -0400, Dan Williams wrote:
>> In preparation for the pmem driver attaching to pmem-namespaces emitted
>> by libnd, convert it to use an ida instead of an always increasing
>> atomic index. This provides a bit of stability to pmem device names in
>> the presence of driver re-bind events.
>> @@ -122,20 +123,26 @@ static struct pmem_device *pmem_alloc(struct device *dev,
struct resource *res)
>> struct pmem_device *pmem;
>> struct gendisk *disk;
>> - int idx, err;
>> + int err;
>> err = -ENOMEM;
>> pmem = kzalloc(sizeof(*pmem), GFP_KERNEL);
>> if (!pmem)
>> goto out;
>> + pmem->id = ida_simple_get(&pmem_ida, 0, 0, GFP_KERNEL);
> nd_pmem_probe() is called asynchronously via async_schedule_domain
> (). We have seen a case that the region#->pmem# binding becomes
> inconsistent across a reboot when there are 8 NVDIMM cards (reported by
> Robert Elliott). This leads user to access a wrong device.
> I think pmem id needs to be assigned before async_schedule_domain(), and
> cascaded to nd_pmem_probe().
I'll take a look at making this better, but it will never be
bulletproof. For the same reason that root=UUID=<uuid> is preferred
over root=/dev/sda userspace should never rely on consistent pmem
device names from boot to boot.
I agree that constant unique IDs, such as UUIDs, are necessary to
guarantee their consistent numbering regardless of configuration
changes. For now, /dev/pmem%d should have consistent numbering while
NFIT table entries are consistent.