linux-kernel - Re: [PATCH] splice: direct call for default_file

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Message-ID: <239aacf6-5f8b-39f4-b4f0-e22de4c46b88@gmail.com>
Date:   Fri, 31 Jan 2020 12:52:27 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] splice: direct call for default_file_splice*()

On 1/30/2020 7:54 PM, Christoph Hellwig wrote:
> On Mon, Jan 20, 2020 at 11:49:46PM +0300, Pavel Begunkov wrote:
>> Indirect calls could be very expensive nowadays, so try to use direct calls
>> whenever possible.
> 
> ... and independent of that your new version is much shorter and easier
> to read.  But it could be improved a tiny little bit further:
> 
>>  	if (out->f_op->splice_write)
>> -		splice_write = out->f_op->splice_write;
>> +		return out->f_op->splice_write(pipe, out, ppos, len, flags);
>>  	else
>> -		splice_write = default_file_splice_write;
>> -
>> -	return splice_write(pipe, out, ppos, len, flags);
>> +		return default_file_splice_write(pipe, out, ppos, len, flags);
> 
> No need for the else after an return.

It generates identical binary. For this to not look sloppy, I'd add new
line between, so the same 4 lines. And this looks better for me, but
that's rather subjective.

I don't think it's worth of changing. What's the benefit?

> 
>>  	if (in->f_op->splice_read)
>> -		splice_read = in->f_op->splice_read;
>> +		return in->f_op->splice_read(in, ppos, pipe, len, flags);
>>  	else
>> -		splice_read = default_file_splice_read;
>> -
>> -	return splice_read(in, ppos, pipe, len, flags);
>> +		return default_file_splice_read(in, ppos, pipe, len, flags);
> 
> Same here.
> 

-- 
Pavel Begunkov