# Re: \[PATCH 25/29\] ext4: use sb\_bdev\_nr\_blocks

- From: Kees Cook \<hidden\>
- Date: 2021-10-13 06:29:45 
- List: linux-block
- Page: https://ratatoskr.run/linux-block/2021/10/215862
- Thread: https://ratatoskr.run/linux-block/2021/10/215820/t.md

```text
On Wed, Oct 13, 2021 at 07:10:38AM +0200, Christoph Hellwig wrote:
> Use the sb_bdev_nr_blocks helper instead of open coding it.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/ext4/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 0775950ee84e3..3dde8be5df490 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4468,7 +4468,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  		goto cantfind_ext4;
>  
>  	/* check blocks count against device size */
> -	blocks_count = sb->s_bdev->bd_inode->i_size >> sb->s_blocksize_bits;
> +	blocks_count = sb_bdev_nr_blocks(sb);

Is s_blocksize_bits always 9 here? If not, this isn't equivalent.

-Kees

>  	if (blocks_count && ext4_blocks_count(es) > blocks_count) {
>  		ext4_msg(sb, KERN_WARNING, "bad geometry: block count %llu "
>  		       "exceeds size of device (%llu blocks)",
> -- 
> 2.30.2
> 

-- 
Kees Cook
```