linux-kernel - Re: [PATCH 1/8] cfq-iosched: simplify control flow in cfq_get

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Message-ID: <x49vbeyhwsb.fsf@segfault.boston.devel.redhat.com>
Date:	Mon, 08 Jun 2015 14:36:52 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	axboe@...nel.dk, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, vgoyal@...hat.com,
	avanzini.arianna@...il.com
Subject: Re: [PATCH 1/8] cfq-iosched: simplify control flow in cfq_get_queue()

Tejun Heo <tj@...nel.org> writes:

> cfq_get_queue()'s control flow looks like the following.
>
> 	async_cfqq = NULL;
> 	cfqq = NULL;
>
> 	if (!is_sync) {
> 		...
> 		async_cfqq = ...;
> 		cfqq = *async_cfqq;
> 	}
>
> 	if (!cfqq)
> 		cfqq = ...;
>
> 	if (!is_sync && !(*async_cfqq))
> 		...;
>
> The only thing the local variable init, the second if, and the
> async_cfqq test in the third if achieves is to skip cfqq creation and
> installation if *async_cfqq was already non-NULL.  This is needlessly
> complicated with different tests examining the same condition.
> Simplify it to the following.
>
> 	if (!is_sync) {
> 		...
> 		async_cfqq = ...;
> 		cfqq = *async_cfqq;
> 		if (cfqq)
> 			goto out;
> 	}
>
> 	cfqq = ...;
>
> 	if (!is_sync)
> 		...;
>  out:
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: Arianna Avanzini <avanzini.arianna@...il.com>

Acked-by: Jeff Moyer <jmoyer@...hat.com>
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