On Wed, 2015-04-29 at 11:59 -0700, Dan Williams wrote: > On Wed, Apr 29, 2015 at 11:25 AM, Toshi Kani <[email protected]> wrote: > > 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. Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
