On Mon, Nov 18, 2019 at 1:52 AM Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com> wrote: > > Dan Williams <dan.j.willi...@intel.com> writes: > > > On Sat, Nov 16, 2019 at 4:15 AM Aneesh Kumar K.V > > <aneesh.ku...@linux.ibm.com> wrote: > >> > > .... > > > >> > >> Considering the direct-map map size is not going to be user selectable, > >> do you agree that we can skip the above step 0 configuration you > >> suggested. > >> > >> The changes proposed in the patch series essentially does the rest. > >> > >> 1) It validate the size against the arch specific limit during > >> namespace creation. (part of step 1) > > > > This validation is a surprise failure to ndctl. > > > >> 2) It also disable initializing a region if it find the size not > >> correctly aligned as per the platform requirement. > > > > There needs to be a way for the user to discover the correct alignment > > that the kernel will accept. > > > >> 3) Direct map mapping size is different from supported_alignment for a > >> namespace. The supported alignment controls what possible PAGE SIZE user > >> want the > >> namespace to be mapped to user space. > > > > No, the namespace alignment is different than the page mapping size. > > The alignment is only interpreted as a mapping size at the device-dax > > level, otherwise at the raw namespace level it's just an arbitrary > > alignment. > > > >> With the above do you think the current patch series is good? > > > > I don't think we've quite converged on a solution. > > How about we make it a property of seed device. ie, > we add `supported_size_align` RO attribute to the seed device. ndctl can > use this to validate the size value. So this now becomes step0 > > sys/bus/nd/devices/region0> cat btt0.0/supported_size_align > 16777216 > /sys/bus/nd/devices/region0> cat pfn0.0/supported_size_align > 16777216 > /sys/bus/nd/devices/region0> cat dax0.0/supported_size_align > 16777216
Why on those devices and not namespace0.0? > We follow that up with validating the size value written to size > attribute(step 1). > > While initializing the namespaces already present in a region we again > validate the size and if not properly aligned we mark the region > disabled. The region might have a mix of namespaces, some aligned and some not, only the misaligned namespaces should fail to enable. The region should otherwise enable successfully.
