On Fri, Jan 18, 2019 at 12:38 AM Dan Williams <[email protected]> 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.
I was wrong, thankfully! nd_pfn_init() *does* call nd_pfn_validate(), I was just overlooking it. I also don't see that this fix is needed. nd_dax_probe() devm-allocates pfn_sb and performs a validation. If the validation succeeds nd_dax_probe() returns 0 which creates a new device and then causes nd_pmem_probe() to fail. At that point devm frees the pfn_sb allocation. The allocation is also freed if the validation step failed. _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
