linux-kernel - Re: [PATCH] fs: dcache: Use bool return value instead of int

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Message-ID: <20160112222105.GT17997@ZenIV.linux.org.uk>
Date:	Tue, 12 Jan 2016 22:21:05 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Chen Gang <chengang@...ndsoft.com.cn>
Cc:	dhowells@...hat.com, akpm@...ux-foundation.org,
	nicolas.iooss_linux@....org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] fs: dcache: Use bool return value instead of int

On Wed, Jan 13, 2016 at 05:42:20AM +0800, Chen Gang wrote:

> For me, it really generates a little better code:
> 
>  - Both 1-word store and 1-byte store are 1 instruction, normally, they
>    have the same execution speed (although it is not quite precise).
> 
>  - But 1-byte store instruction has short length under CISC archs, which
>    can generate a little better code globally.
> 
>  - For most of archs, 1-word store can process bytes nonalignment cases,
>    for check_mount() individually, the parameter data may be not word
>    alignment, which may cause the 1-word store slower than 1-byte store.

What the hell do you mean, unaligned?  It's given an address of local
variable of type int; it _will_ be aligned, or the compiler is FUBAR.

As for the inlines... frankly, if gcc generates a different code from having
replaced int with bool in those, it's time to do something very nasty to
gcc developers.