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. _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
