linux-kernel - Re: [PATCH v4 4/4] fs/proc/vmcore: Use iov_iter

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Message-ID: <YjSOExYBbpZ7Hw8Z@casper.infradead.org>
Date:   Fri, 18 Mar 2022 13:50:11 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     'Baoquan He' <bhe@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "yangtiezhu@...ngson.cn" <yangtiezhu@...ngson.cn>,
        "amit.kachhap@....com" <amit.kachhap@....com>,
        "hch@....de" <hch@....de>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v4 4/4] fs/proc/vmcore: Use iov_iter_count()

On Fri, Mar 18, 2022 at 01:48:07PM +0000, David Laight wrote:
> For some definition of 'cleaner' :-)
> 
> iter->count is clearly a simple, cheap structure member lookup.
> OTOH iov_iter_count(iter) might be an expensive traversal of
> the vector (or worse).
> 
> So a quick read of the code by someone who isn't an expert
> in the iov functions leaves them wondering what is going on
> or having to spend time locating the definition ...

Thank you for having an opinion.  Al's opinion, as the iov_iter
maintainer, trumps yours.