libnvdimm, dax: record the specified alignment of a dax-device instance

We want to use the alignment as the allocation and mapping unit.
Previously this information was only useful for establishing the data
offset, but now it is important to remember the granularity for the
later use.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

2 files changed, 9 insertions, 3 deletions

diff --git a/drivers/nvdimm/pfn.h b/drivers/nvdimm/pfn.h
index 8e343a3ca873..9d2704c83fa7 100644
--- a/drivers/nvdimm/pfn.h
+++ b/drivers/nvdimm/pfn.h
@@ -33,7 +33,9 @@ struct nd_pfn_sb {
         /* minor-version-1 additions for section alignment */
         __le32 start_pad;
         __le32 end_trunc;
-        u8 padding[4004];
+        /* minor-version-2 record the base alignment of the mapping */
+        __le32 align;
+        u8 padding[4000];
         __le64 checksum;
 };
 
diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index ca396c8f2cd5..58740d7ce81b 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -394,6 +394,9 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn)
                 pfn_sb->end_trunc = 0;
         }
 
+        if (__le16_to_cpu(pfn_sb->version_minor) < 2)
+                pfn_sb->align = 0;
+
         switch (le32_to_cpu(pfn_sb->mode)) {
         case PFN_MODE_RAM:
         case PFN_MODE_PMEM:
@@ -433,7 +436,7 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn)
                 return -EBUSY;
         }
 
-        nd_pfn->align = 1UL << ilog2(offset);
+        nd_pfn->align = le32_to_cpu(pfn_sb->align);
         if (!is_power_of_2(offset) || offset < PAGE_SIZE) {
                 dev_err(&nd_pfn->dev, "bad offset: %#llx dax disabled\n",
                                 offset);
@@ -629,9 +632,10 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
         memcpy(pfn_sb->uuid, nd_pfn->uuid, 16);
         memcpy(pfn_sb->parent_uuid, nd_dev_to_uuid(&ndns->dev), 16);
         pfn_sb->version_major = cpu_to_le16(1);
-        pfn_sb->version_minor = cpu_to_le16(1);
+        pfn_sb->version_minor = cpu_to_le16(2);
         pfn_sb->start_pad = cpu_to_le32(start_pad);
         pfn_sb->end_trunc = cpu_to_le32(end_trunc);
+        pfn_sb->align = cpu_to_le32(nd_pfn->align);
         checksum = nd_sb_checksum((struct nd_gen_sb *) pfn_sb);
         pfn_sb->checksum = cpu_to_le64(checksum);