On Fri, Mar 26, 2021 at 11:27 AM Tyler Hicks
<tyhi...@linux.microsoft.com> wrote:
>
> 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 <tyhi...@linux.microsoft.com>This solves the problem that I had in this thread: https://lore.kernel.org/lkml/ca+ck2bcd13jblmxn2mauryvqgkbs5ic2uqyssxxtccszxcm...@mail.gmail.com/ Thank you Tyler for root causing and finding a proper fix. Reviewed-by: Pavel Tatashin <pasha.tatas...@soleen.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; > + } > + > /* > * Given that space allocation consults this value multiple > * times ensure it does not change for the duration of the > -- > 2.25.1 >
