Messages in this thread | | | Date | Tue, 30 Mar 2021 10:43:15 -0500 | From | Tyler Hicks <> | Subject | Re: [PATCH] libnvdimm/region: Allow setting align attribute on regions without mappings |
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On 2021-03-30 16:32:10, Aneesh Kumar K.V wrote: > Tyler Hicks <tyhicks@linux.microsoft.com> writes: > > > The alignment constraint for namespace creation in a region was > > increased, from 2M to 16M, for non-PowerPC architectures in v5.7 with > > commit 2522afb86a8c ("libnvdimm/region: Introduce an 'align' > > attribute"). The thought behind the change was that region alignment > > should be uniform across all architectures and, since PowerPC had the > > largest alignment constraint of 16M, all architectures should conform to > > that alignment. > > > > The change regressed namespace creation in pre-defined regions that > > relied on 2M alignment but a workaround was provided in the form of a > > sysfs attribute, named 'align', that could be adjusted to a non-default > > alignment value. > > > > However, the sysfs attribute's store function returned an error (-ENXIO) > > when userspace attempted to change the alignment of a region that had no > > mappings. This affected 2M aligned regions of volatile memory that were > > defined in a device tree using "pmem-region" and created by the > > of_pmem_region_driver, since those regions do not contain mappings > > (ndr_mappings is 0). > > > > Allow userspace to set the align attribute on pre-existing regions that > > do not have mappings so that namespaces can still be within those > > regions, despite not being aligned to 16M. > > > > Fixes: 2522afb86a8c ("libnvdimm/region: Introduce an 'align' attribute") > > Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com> > > --- > > drivers/nvdimm/region_devs.c | 33 ++++++++++++++++++--------------- > > 1 file changed, 18 insertions(+), 15 deletions(-) > > > > diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c > > index ef23119db574..09cff8aa6b40 100644 > > --- a/drivers/nvdimm/region_devs.c > > +++ b/drivers/nvdimm/region_devs.c > > @@ -545,29 +545,32 @@ static ssize_t align_store(struct device *dev, > > struct device_attribute *attr, const char *buf, size_t len) > > { > > struct nd_region *nd_region = to_nd_region(dev); > > - unsigned long val, dpa; > > - u32 remainder; > > + unsigned long val; > > int rc; > > > > rc = kstrtoul(buf, 0, &val); > > if (rc) > > return rc; > > > > - if (!nd_region->ndr_mappings) > > - return -ENXIO; > > - > > - /* > > - * Ensure space-align is evenly divisible by the region > > - * interleave-width because the kernel typically has no facility > > - * to determine which DIMM(s), dimm-physical-addresses, would > > - * contribute to the tail capacity in system-physical-address > > - * space for the namespace. > > - */ > > - dpa = div_u64_rem(val, nd_region->ndr_mappings, &remainder); > > - if (!is_power_of_2(dpa) || dpa < PAGE_SIZE > > - || val > region_size(nd_region) || remainder) > > + if (val > region_size(nd_region)) > > return -EINVAL; > > > > + if (nd_region->ndr_mappings) { > > + unsigned long dpa; > > + u32 remainder; > > + > > + /* > > + * Ensure space-align is evenly divisible by the region > > + * interleave-width because the kernel typically has no facility > > + * to determine which DIMM(s), dimm-physical-addresses, would > > + * contribute to the tail capacity in system-physical-address > > + * space for the namespace. > > + */ > > + dpa = div_u64_rem(val, nd_region->ndr_mappings, &remainder); > > + if (!is_power_of_2(dpa) || dpa < PAGE_SIZE || remainder) > > + return -EINVAL; > > + } > > We still want > > else { > > if (!is_power_of_2(val) || val < PAGE_SIZE) > return -EINVAL?
Yes, very good point. I'll send out a v2 that ensures val is a power of 2 and at least page size.
Tyler
> > } > > + > > /* > > * Given that space allocation consults this value multiple > > * times ensure it does not change for the duration of the > > -- > > 2.25.1 > > _______________________________________________ > > Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org > > To unsubscribe send an email to linux-nvdimm-leave@lists.01.org >
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