linux-kernel - Re: [PATCH v9 02/13] exfat: add super block operations

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Date:   Wed, 8 Jan 2020 18:21:35 +0100
From:   Christoph Hellwig <hch@....de>
To:     Namjae Jeon <namjae.jeon@...sung.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        gregkh@...uxfoundation.org, valdis.kletnieks@...edu, hch@....de,
        sj1557.seo@...sung.com, linkinjeon@...il.com, pali.rohar@...il.com
Subject: Re: [PATCH v9 02/13] exfat: add super block operations

Looks good, modulo a few nitpicks below:

Reviewed-by: Christoph Hellwig <hch@....de>

On Thu, Jan 02, 2020 at 04:20:25PM +0800, Namjae Jeon wrote:
> +static int exfat_statfs(struct dentry *dentry, struct kstatfs *buf)
> +{
> +	struct super_block *sb = dentry->d_sb;
> +	struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +	unsigned long long id = huge_encode_dev(sb->s_bdev->bd_dev);

> +	if (sbi->used_clusters == ~0u) {

Various other places use UINT_MAX here instead.  Maybe it makes sense
to add a EXFAT_CLUSTERS_UNTRACKED or similar define and use that in all
places?

> +	if ((new_flag == VOL_DIRTY) && (!buffer_dirty(sbi->pbr_bh)))

No need for both sets of inner braces.

> +static bool is_exfat(struct pbr *pbr)
> +{
> +	int i = MUST_BE_ZERO_LEN;
> +
> +	do {
> +		if (pbr->bpb.f64.res_zero[i - 1])
> +			break;
> +	} while (--i);
> +	return i ? false : true;
> +}

I find the MUST_BE_ZERO_LEN a little weird here.  Maybe that should
be something like PBP64_RESERVED_LEN?

Also I think this could be simplified by just using memchr_inv in the
caller

	if (memchr_inv(pbr->bpb.f64.res_zero, 0,
			sizeof(pbr->bpb.f64.res_zero)))
		ret = -EINVAL;
		goto free_bh;
	}

> +	/* set maximum file size for exFAT */
> +	sb->s_maxbytes = 0x7fffffffffffffffLL;

That this is setting the max size is pretty obvious.  Maybe the comment
should be updated to mention how this max file size is calculated?