[PATCH v2] nvdimm, btt: add a size attribute for BTTs

[Vishal Verma]

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

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

v2:
- Use the correct locking in size_show (Dan)
- Use a typecast for 64b multiplication

 drivers/nvdimm/btt.c      |  1 +
 drivers/nvdimm/btt_devs.c | 20 ++++++++++++++++++++
 drivers/nvdimm/nd.h       |  1 +
 3 files changed, 22 insertions(+)

diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index 68a7c3c..e0084ae 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -1270,6 +1270,7 @@ 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 3fa7919..97dd292 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 4047639..8024a0e 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;
 };
-- 
2.7.4

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