linux-kernel - Re: [PATCH v4 1/3] random: convert to using fops->read

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Message-ID: <35a5ff9f-79d7-feb5-dfa7-a775b9352416@kernel.dk>
Date:   Fri, 20 May 2022 08:36:17 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>, Christoph Hellwig <hch@....de>,
        LKML <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v4 1/3] random: convert to using fops->read_iter()

On 5/20/22 7:37 AM, Jason A. Donenfeld wrote:
> On Fri, May 20, 2022 at 11:44:57AM +0200, Jason A. Donenfeld wrote:
>>  const struct file_operations urandom_fops = {
>> -	.read = urandom_read,
>> +	.read_iter = urandom_read_iter,
> 
> One thing I noticed is that drivers/char/mem.c has both the .read and
> the .read_iter functions for /dev/zero and /dev/null and such. I wonder
> if the .read ones can be removed?

I'm not sure if we have a clear "always use this if available" set of
rules for this. Ideally we'd want it to be:

1) Use ->read_iter() if available
2) If not, use ->read()

Might require a bit of auditing to ensure that's the case, and if we
can say that it is, then we could clean that up too.

-- 
Jens Axboe