Messages in this thread | | | From | Dan Williams <> | Date | Mon, 21 Jan 2019 17:00:47 -0800 | Subject | Re: [PATCH] libnvdimm: Clarify nd_pfn_init() flow |
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On Mon, Jan 21, 2019 at 4:47 PM Wei Yang <richardw.yang@linux.intel.com> wrote: > > On Mon, Jan 21, 2019 at 04:29:08PM -0800, Dan Williams wrote: > >On Mon, Jan 21, 2019 at 4:26 PM Wei Yang <richardw.yang@linux.intel.com> wrote: > >[..] > >> >@@ -706,6 +711,22 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn) > >> > sig = DAX_SIG; > >> > else > >> > sig = PFN_SIG; > >> >+ > >> >+ /* > >> >+ * Check for an existing 'pfn' superblock before writing a new > >> >+ * one. The intended flow is that on the first probe of an > >> >+ * nd_{pfn,dax} device the superblock is calculated and written > >> >+ * to the namespace. In this case nd_pfn_validate() returns > >> >+ * -ENODEV because no valid superblock exists currently. > >> > >> As you replied in following mail: > >> > >> 3/ If present, nd_pfn_validate() returns 0 and nd_dax_probe() > >> registers the dax0.1 device (this is a libnvdimm 'personality device). > >> > >> So at this point, nd_pfn_validate() return 0 or -ENODEV? > > > >In this case 0, because the configuration was successfully validated. > > > >-ENODEV, is only returned for the initial case where we want the > >kernel to write the configuration. > > > >All other error codes are an actual failure and the probe procedure stops. > > To be honest, this maybe crystal clear for you. But I still feel a little > confused. Especially on differentiating those cases. How many cases we have?
There are 4 cases:
1/ namespace probed, no personality info-block found, namespace results in 'raw' mode
2/ namespace probed, {pfn,btt,dax} info-block found, {pfn,btt,dax} device created and attached to the corresponding personality driver
3/ namespace probing ends in failure like -ENOMEM, or a -EIO error reading namespace capacity, for example due to a bad block.
4/ namespace force assigned to a {pfn,btt,dax} device instance, {pfn,btt,dax} device force enabled leading to the info-block being written out to the device
> And what's your first probe mean? This the nd_btt/pfn/dax_probe()? or the > linux driver probe?
The first probe is always nd_pmem_probe(). nd_{pfn,btt,dax}_probe() are secondary.
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