Messages in this thread | | | Date | Wed, 29 Apr 2015 11:59:35 -0700 | Subject | Re: [Linux-nvdimm] [PATCH v2 10/20] pmem: use ida | From | Dan Williams <> |
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On Wed, Apr 29, 2015 at 11:25 AM, Toshi Kani <toshi.kani@hp.com> 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.
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