# Re: \[PATCH 12/29\] cramfs: use bdev\_nr\_sectors instead of open coding it

- From: Kees Cook \<hidden\>
- Date: 2021-10-13 06:16:16 
- List: linux-ext4
- Page: https://ratatoskr.run/linux-ext4/2021/10/215857
- Thread: https://ratatoskr.run/linux-block/2021/10/215820/t.md

```text
On Wed, Oct 13, 2021 at 07:10:25AM +0200, Christoph Hellwig wrote:
> Use the proper helper to read the block device size.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/cramfs/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> index 2be65269a987c..3e44cc3ed0543 100644
> --- a/fs/cramfs/inode.c
> +++ b/fs/cramfs/inode.c
> @@ -209,7 +209,7 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
>  		return read_buffers[i] + blk_offset;
>  	}
>  
> -	devsize = mapping->host->i_size >> PAGE_SHIFT;
> +	devsize = bdev_nr_sectors(sb->s_bdev) >> (PAGE_SHIFT - SECTOR_SHIFT);

I find this less readable than "bytes >> PAGE_SHIFT". I'd suggest this
use a new bdev_nr_bytes() helper.

-- 
Kees Cook
```