On Thu, Jan 17, 2019 at 09:05:54PM -0800, Dan Williams wrote: >On Thu, Jan 17, 2019 at 9:03 PM Wei Yang <richardw.y...@linux.intel.com> wrote: >> >> On Thu, Jan 17, 2019 at 08:31:56PM -0800, Dan Williams wrote: >> >On Thu, Jan 17, 2019 at 7:36 PM Wei Yang <richardw.y...@linux.intel.com> >> >wrote: >> >> >> >> In current implementation, we might re-allocate nd_pfn->pfn_sb. >> >> >> >> For example: >> >> >> >> nd_dax_probe() >> >> nd_pfn->pfn_sb = devm_kzalloc() >> >> >> >> dax_pmem_probe() >> >> nvdimm_setup_pfn() >> >> nd_pfn_init() >> >> nd_pfn->pfn_sb = devm_kzalloc() >> >> >> >> This patch checks nd_pfn->pfn_sb before allocating it in nd_pfn_init(). >> > >> >Ugh, this patch is unfortunately uncovering a deeper problem. >> >nvdimm_setup_pfn() should not be calling nd_pfn_init(). This >> >effectively is always re-initializing the info-block, benign but >> >unnecessary. Instead it needs to be using nd_pfn_validate() followed >> >by an __nvdimm_setup_pfn() in the dax_pmem_probe() path. >> > >> >Good find! >> >> So we should fix this like: >> >> dax_pmem_probe() >> nd_pfn_validate() >> __nvdimm_setup_pfn() >> >> Is my understanding correct? > >Yes, at first glance, but it would need a deeper review and testing. >The usage of nvdimm_setup_pfn() in drivers/nvdimm/pmem.c needs a >similar fixup.
I went through the code again and found I may remove the allocation in nd_pfn_init(). Below is my analysis. nvdimm_setup_pfn() is invoked in two places: * dax_pmem_probe() * pmem_attach_disk(), when it is_nd_pfn() And before these two function called, corresponding device should be allocated and created. And we can see these two corresponding places to create the devices are: * nd_dax_probe() * nd_pfn_probe() Both of them allocate pfn_sb. This means it is not necessary to allocate it again when we do the probe function. Do you think it looks good to you? -- Wei Yang Help you, Help me _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm
