From 2e5021cc42ba26c98fe83b973d774a999fa4f219 Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Tue, 30 Aug 2022 00:45:05 -0500 Subject: [PATCH] libnvdimm/region: Allow setting align attribute on regions without mappings 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. Link: https://lore.kernel.org/lkml/CA+CK2bDJ3hrWoE91L2wpAk+Yu0_=GtYw=4gLDDD7mxs321b_aA@mail.gmail.com Fixes: 2522afb86a8c ("libnvdimm/region: Introduce an 'align' attribute") Signed-off-by: Tyler Hicks Link: https://lore.kernel.org/r/20220830054505.1159488-1-tyhicks@linux.microsoft.com Signed-off-by: Dan Williams --- drivers/nvdimm/region_devs.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c index 70f1a23..e0875d36 100644 --- a/drivers/nvdimm/region_devs.c +++ b/drivers/nvdimm/region_devs.c @@ -509,16 +509,13 @@ static ssize_t align_store(struct device *dev, { struct nd_region *nd_region = to_nd_region(dev); unsigned long val, dpa; - u32 remainder; + u32 mappings, remainder; 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 @@ -526,7 +523,8 @@ static ssize_t align_store(struct device *dev, * contribute to the tail capacity in system-physical-address * space for the namespace. */ - dpa = div_u64_rem(val, nd_region->ndr_mappings, &remainder); + mappings = max_t(u32, 1, nd_region->ndr_mappings); + dpa = div_u64_rem(val, mappings, &remainder); if (!is_power_of_2(dpa) || dpa < PAGE_SIZE || val > region_size(nd_region) || remainder) return -EINVAL; -- 2.7.4