nvdimm/region: Fix default alignment for small regions

In preparation for removing BLK aperture support the NVDIMM unit tests
discovered that the default alignment can be set higher than the
capacity of the region. Fall back to PAGE_SIZE in that case.

Given this has not been seen in the wild, elide notifying -stable.

Fixes: 2522afb86a8c ("libnvdimm/region: Introduce an 'align' attribute")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/164688416128.2879318.17890707310125575258.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index 9ccf3d608799311820cc4a58abd7d56777767cdd..70ad891a76bae3cbdaf690d2a615babd2063deb1 100644 (file)
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1025,6 +1025,9 @@ static unsigned long default_align(struct nd_region *nd_region)
                }
        }
 
+       if (nd_region->ndr_size < MEMREMAP_COMPAT_ALIGN_MAX)
+               align = PAGE_SIZE;
+
        mappings = max_t(u16, 1, nd_region->ndr_mappings);
        div_u64_rem(align, mappings, &remainder);
        if (remainder)