linux-ext4 - Re: [PATCH 24/29] block: add a sb_bdev_nr

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Date:   Tue, 12 Oct 2021 23:27:42 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>, Coly Li <colyli@...e.de>,
        Mike Snitzer <snitzer@...hat.com>, Song Liu <song@...nel.org>,
        David Sterba <dsterba@...e.com>,
        Josef Bacik <josef@...icpanda.com>,
        Theodore Ts'o <tytso@....edu>,
        OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        Dave Kleikamp <shaggy@...nel.org>,
        Ryusuke Konishi <konishi.ryusuke@...il.com>,
        Anton Altaparmakov <anton@...era.com>,
        Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
        Phillip Lougher <phillip@...ashfs.org.uk>,
        Jan Kara <jack@...e.com>, linux-block@...r.kernel.org,
        dm-devel@...hat.com, drbd-dev@...ts.linbit.com,
        linux-bcache@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-mtd@...ts.infradead.org, linux-nvme@...ts.infradead.org,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, jfs-discussion@...ts.sourceforge.net,
        linux-nfs@...r.kernel.org, linux-nilfs@...r.kernel.org,
        linux-ntfs-dev@...ts.sourceforge.net, ntfs3@...ts.linux.dev,
        reiserfs-devel@...r.kernel.org
Subject: Re: [PATCH 24/29] block: add a sb_bdev_nr_blocks helper

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@....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