nvdimm, btt: add a size attribute for BTTs

To be consistent with other namespaces, expose a 'size' attribute for
BTT devices also.

Cc: Dan Williams <dan.j.williams@intel.com>
Reported-by: Linda Knippers <linda.knippers@hpe.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

3 files changed, 22 insertions, 0 deletions

diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index 88e91666f145..368795aad5c9 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -1269,6 +1269,7 @@ static int btt_blk_init(struct btt *btt)
                 }
         }
         set_capacity(btt->btt_disk, btt->nlba * btt->sector_size >> 9);
+        btt->nd_btt->size = btt->nlba * (u64)btt->sector_size;
         revalidate_disk(btt->btt_disk);
 
         return 0;
diff --git a/drivers/nvdimm/btt_devs.c b/drivers/nvdimm/btt_devs.c
index 3fa7919f94a8..97dd2925ed6e 100644
--- a/drivers/nvdimm/btt_devs.c
+++ b/drivers/nvdimm/btt_devs.c
@@ -140,10 +140,30 @@ static ssize_t namespace_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(namespace);
 
+static ssize_t size_show(struct device *dev,
+                struct device_attribute *attr, char *buf)
+{
+        struct nd_btt *nd_btt = to_nd_btt(dev);
+        ssize_t rc;
+
+        device_lock(dev);
+        if (dev->driver)
+                rc = sprintf(buf, "%llu\n", nd_btt->size);
+        else {
+                /* no size to convey if the btt instance is disabled */
+                rc = -ENXIO;
+        }
+        device_unlock(dev);
+
+        return rc;
+}
+static DEVICE_ATTR_RO(size);
+
 static struct attribute *nd_btt_attributes[] = {
         &dev_attr_sector_size.attr,
         &dev_attr_namespace.attr,
         &dev_attr_uuid.attr,
+        &dev_attr_size.attr,
         NULL,
 };
 
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 40476399d227..8024a0ef86d3 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -143,6 +143,7 @@ struct nd_btt {
         struct nd_namespace_common *ndns;
         struct btt *btt;
         unsigned long lbasize;
+        u64 size;
         u8 *uuid;
         int id;
 };