[lkml]   [2019]   [Jan]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] libnvdimm: Clarify nd_pfn_init() flow
On Sun, Jan 20, 2019 at 11:51 PM Wei Yang <> wrote:
> On Fri, Jan 18, 2019 at 04:47:23PM -0800, Dan Williams wrote:
> Also, I have one confusion about your saying: two probes.
> If the two probes are:
> * for dax%d.%d: 1. nd_dax_probe 2. dax_pmem_probe
> * for pfn%d.%d: 1. nd_pfn_probe 2. nd_pmem_probe
> Then, if the first probe fails, the device itself would be destroyed. How the
> second probe do its job?
> > rc = nd_pfn_validate(nd_pfn, sig);
> > if (rc != -ENODEV)
> > return rc;

Here is an example path for a device-dax instance:


In this case the order of events is:

1/ region0 discovers it contains a pmem namespace and registers namespace0.0
2/ The pmem namespace driver calls nd_dax_probe() to check for the
presence of a device-dax configuration
3/ If present, nd_pfn_validate() returns 0 and nd_dax_probe()
registers the dax0.1 device (this is a libnvdimm 'personality device).
4/ When nd_pmem_probe() sees nd_dax_probe() return 0 it in turn fails
the probe of namespace0.0 with -ENXIO. All devm allocations during the
probe of namespace0.0 are released.
5/ Meanwhile the created dax0.1 device is recognized by the dax_pmem device.
6/ dax_pmem_probe() uses nd_pfn_init() to validate the configuration
and ultimately creates the dax0.0 character device

The pmem namepsace driver is effectively a router to other personality
drivers that may be layered on top of the base namespace capacity.

 \ /
  Last update: 2019-01-21 19:05    [W:0.092 / U:25.900 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site