linux-kernel - Re: [PATCH v7] iomap: make inline data support more flexible

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Message-ID: <20210726121702.GA528@lst.de>
Date:   Mon, 26 Jul 2021 14:17:02 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andreas Gruenbacher <agruenba@...hat.com>
Cc:     Gao Xiang <hsiangkao@...ux.alibaba.com>,
        Christoph Hellwig <hch@....de>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Huang Jianan <huangjianan@...o.com>,
        linux-erofs@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Andreas Gruenbacher <andreas.gruenbacher@...il.com>
Subject: Re: [PATCH v7] iomap: make inline data support more flexible

> Subject: iomap: Support tail packing

I can't say I like this "tail packing" language here when we have the
perfectly fine inline wording.  Same for various comments in the actual
code.

> +	/* inline and tail-packed data must start page aligned in the file */
> +	if (WARN_ON_ONCE(offset_in_page(iomap->offset)))
> +		return -EIO;
> +	if (WARN_ON_ONCE(size > PAGE_SIZE - offset_in_page(iomap->inline_data)))
> +		return -EIO;

Why can't we use iomap_inline_data_size_valid here? That is how can
size be different from iomap->legth?

Shouldn't the offset_in_page also go into iomap_inline_data_size_valid,
which should probably be called iomap_inline_data_valid then?

>  	if (iomap->type == IOMAP_INLINE) {
> +		int ret = iomap_read_inline_data(inode, page, iomap);
> +		return ret ?: PAGE_SIZE;

The ?: expression without the first leg is really confuing.  Especially
if a good old if is much more readable here.

		int ret = iomap_read_inline_data(inode, page, iomap);

		if (ret)
			return ret;
		return PAGE_SIZE;

> +		copied = copy_from_iter(iomap_inline_data(iomap, pos), length, iter);


> +		copied = copy_to_iter(iomap_inline_data(iomap, pos), length, iter);

Pleae avoid the overly long lines.