linux-ext4 - Re: [PATCH 25/29] ext4: use sb_bdev_nr

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Message-ID: <202110122328.92B4FC41F4@keescook>
Date:   Tue, 12 Oct 2021 23:29:39 -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 25/29] ext4: use sb_bdev_nr_blocks

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@....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