Messages in this thread | | | From | Dan Williams <> | Date | Mon, 21 Jan 2019 10:04:40 -0800 | Subject | Re: [PATCH] libnvdimm: Clarify nd_pfn_init() flow |
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On Sun, Jan 20, 2019 at 11:51 PM Wei Yang <richardw.yang@linux.intel.com> 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:
/sys/devices/platform/e820_pmem/ndbus0/region0/dax0.1/dax0.0
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.
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