linux-ext4 - Re: [PATCH 12/29] cramfs: use bdev_nr_sectors instead of open coding it

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Date:   Tue, 12 Oct 2021 23:16:11 -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 12/29] cramfs: use bdev_nr_sectors instead of open coding
 it

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@....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