drbd: use bdev_nr_sectors instead of open coding it

Use the proper helper to read the block device size.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20211018101130.1838532-5-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/drbd/drbd_int.h

@@ -1826,8 +1826,7 @@ static inline sector_t drbd_md_last_sector(struct drbd_backing_dev *bdev)
 /* Returns the number of 512 byte sectors of the device */
 static inline sector_t drbd_get_capacity(struct block_device *bdev)
 {
-	/* return bdev ? get_capacity(bdev->bd_disk) : 0; */
-	return bdev ? i_size_read(bdev->bd_inode) >> 9 : 0;
+	return bdev ? bdev_nr_sectors(bdev) : 0;
 }
 
 /**