On Fri, Jan 18, 2019 at 12:38:18AM -0800, Dan Williams wrote: >On Thu, Jan 17, 2019 at 11:31 PM Wei Yang <[email protected]> >wrote: >> >> On Thu, Jan 17, 2019 at 09:05:54PM -0800, Dan Williams wrote: >> >On Thu, Jan 17, 2019 at 9:03 PM Wei Yang <[email protected]> >> >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 <[email protected]> >> >> >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? >> > >No it doesn't because the real issue is that we should not be >recreating the info block. So the fix is not avoiding the allocation, >the fix is avoiding nd_pfn_init() in the probe path altogether.
Hmm... I may lost here. Which info block we recreated? For one particular device type, nvdimm_setup_pfn() is just called once. By preventing re-allocation here is enough to me. I may not get your point here. Would you mind share some light on this place? -- Wei Yang Help you, Help me _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
