linux-kernel - Re: [PATCH 2/6] iov_iter: new iov_iter_pin_pages*(), for FOLL

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Message-ID: <db3b5263-864e-dbb8-b3d9-075b6283e5bf@nvidia.com>
Date:   Sun, 27 Feb 2022 14:09:39 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Jens Axboe <axboe@...nel.dk>, jhubbard.send.patches@...il.com,
        Jan Kara <jack@...e.cz>, Christoph Hellwig <hch@...radead.org>,
        Dave Chinner <dchinner@...hat.com>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Theodore Ts'o <tytso@....edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Miklos Szeredi <miklos@...redi.hu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Chaitanya Kulkarni <kch@...dia.com>
Cc:     linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] iov_iter: new iov_iter_pin_pages*(), for FOLL_PIN
 pages

On 2/27/22 13:57, Jens Axboe wrote:
...
>> +			return res;
>> +		return (res == n ? len : res * PAGE_SIZE) - *start;
> 
> Trying to be clever like that just makes the code a lot less readable. I
> should not have to reason about a return value. Same in the other
> function.
> 

No argument there. This was shamelessly lifted from
iov_iter_get_pages(), and I initially calculated that keeping it
identical to that known-good code, where possible, was better than
fixing it up.

However, I'll go ahead and simplify it--with pleasure--based on this
feedback.


thanks,
-- 
John Hubbard
NVIDIA