libnvdimm, dax: fix alignment validation

Testing the dax-device autodetect support revealed a probe failure with
the following result:

    dax0.1: bad offset: 0x8200000 dax disabled

The original pfn-device implementation inferred the alignment from
ilog2(offset), now that the alignment is explicit the is_power_of_2()
needs replacing with a real sanity check against the recorded alignment.
Otherwise the alignment check is useless in the implicit case and only
the minimum size of the offset matters.

This self-consistency check is further validated by the probe path that
will re-check that the offset is large enough to contain all the
metadata required to enable the device.

Cc: <stable@vger.kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 816cd9828ca5..04f71d6d304d 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -416,6 +416,8 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
                         return -ENODEV;
         }
 
+        if (nd_pfn->align == 0)
+                nd_pfn->align = le32_to_cpu(pfn_sb->align);
         if (nd_pfn->align > nvdimm_namespace_capacity(ndns)) {
                 dev_err(&nd_pfn->dev, "alignment: %lx exceeds capacity %llx\n",
                                 nd_pfn->align, nvdimm_namespace_capacity(ndns));
@@ -436,8 +438,8 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
                 return -EBUSY;
         }
 
-        nd_pfn->align = le32_to_cpu(pfn_sb->align);
-        if (!is_power_of_2(offset) || offset < PAGE_SIZE) {
+        if ((nd_pfn->align && !IS_ALIGNED(offset, nd_pfn->align))
+                        || !IS_ALIGNED(offset, PAGE_SIZE)) {
                 dev_err(&nd_pfn->dev, "bad offset: %#llx dax disabled\n",
                                 offset);
                 return -ENXIO;