linux-kernel - Re: [PATCH v2 2/7] erofs: some marcos are much more readable as a function

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Message-ID: <20190830154551.GA11571@infradead.org>
Date:   Fri, 30 Aug 2019 08:45:51 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Gao Xiang <gaoxiang25@...wei.com>, Chao Yu <yuchao0@...wei.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, LKML <linux-kernel@...r.kernel.org>,
        linux-erofs@...ts.ozlabs.org, Chao Yu <chao@...nel.org>,
        Miao Xie <miaoxie@...wei.com>, weidu.du@...wei.com,
        Fang Wei <fangwei1@...wei.com>
Subject: Re: [PATCH v2 2/7] erofs: some marcos are much more readable as a
 function

On Thu, Aug 29, 2019 at 08:16:27PM -0700, Joe Perches wrote:
> > -		sizeof(__u32) * ((__count) - 1); })
> > +static inline unsigned int erofs_xattr_ibody_size(__le16 d_icount)
> > +{
> > +	unsigned int icount = le16_to_cpu(d_icount);
> > +
> > +	if (!icount)
> > +		return 0;
> > +
> > +	return sizeof(struct erofs_xattr_ibody_header) +
> > +		sizeof(__u32) * (icount - 1);
> 
> Maybe use struct_size()?

Declaring a variable that is only used for struct_size is rather ugly.
But while we are nitpicking: you don't need to byteswap to check for 0,
so the local variable could be avoided.

Also what is that magic -1 for?  Normally we use that for the
deprecated style where a variable size array is declared using
varname[1], but that doesn't seem to be the case for erofs.