Re: [PATCH 24/29] block: add a sb_bdev_nr_blocks helper

[Kees Cook <keescook@chromium.org>]

On Wed, Oct 13, 2021 at 07:10:37AM +0200, Christoph Hellwig wrote:
> Add a helper to return the size of sb->s_bdev in sb->s_blocksize_bits
> based unites.  Note that SECTOR_SHIFT has to be open coded due to
> include dependency issues for now, but I have a plan to sort that out
> eventually.

Wouldn't that just need a quick lift into a new header file to be
included by genhd.h, blkev.h, and:

drivers/mtd/ssfdc.c:#define SECTOR_SHIFT                9
fs/hfsplus/hfsplus_raw.h:#define HFSPLUS_SECTOR_SHIFT         9

I think that's worth doing at some point in this series since genhd.h
already has existing open-coded "9"s. And, really, a *lot* of other
places too:

$ git grep -E '(<<|>>) 9' | grep -E '\b(block|blk|sector|bdev)\b' | wc -l
240

> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  include/linux/genhd.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
> index 082a3e5fd8fa1..6eaef8fa78bcd 100644
> --- a/include/linux/genhd.h
> +++ b/include/linux/genhd.h
> @@ -245,6 +245,12 @@ static inline sector_t get_capacity(struct gendisk *disk)
>  	return bdev_nr_sectors(disk->part0);
>  }
>  
> +static inline u64 sb_bdev_nr_blocks(struct super_block *sb)
> +{
> +	return bdev_nr_sectors(sb->s_bdev) >>
> +		(sb->s_blocksize_bits - 9 /* SECTOR_SHIFT */);
> +}
> +
>  int bdev_disk_changed(struct gendisk *disk, bool invalidate);
>  void blk_drop_partitions(struct gendisk *disk);
>  
> -- 
> 2.30.2
> 

-- 
Kees Cook