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

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Message-ID: <20160111225104.GO17997@ZenIV.linux.org.uk>
Date:	Mon, 11 Jan 2016 22:51:05 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	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, Chen Gang <gang.chen.5i5j@...il.com>
Subject: Re: [PATCH] fs: dcache: Use bool return value instead of int

On Tue, Jan 12, 2016 at 05:30:45AM +0800, chengang@...ndsoft.com.cn wrote:
> From: Chen Gang <gang.chen.5i5j@...il.com>
> 
> Use bool type for all functions which return boolean value. It will not
> only let code clearer, but also sometimes let gcc produce better code.

What's the point of this chunk?

>  static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
>  {
> -	int *ret = data;
> +	bool *ret = data;
>  	if (d_mountpoint(dentry)) {
> -		*ret = 1;
> +		*ret = true;
>  		return D_WALK_QUIT;
>  	}
>  	return D_WALK_CONTINUE;

You are replacing a 1-word store with 1-byte store; if anything, that's more
likely to yield _worse_ code, not better one.

> -static inline int d_unhashed(const struct dentry *dentry)
> +static inline bool d_unhashed(const struct dentry *dentry)
>  {
>  	return hlist_bl_unhashed(&dentry->d_hash);
>  }
>  
> -static inline int d_unlinked(const struct dentry *dentry)
> +static inline bool d_unlinked(const struct dentry *dentry)
>  {
>  	return d_unhashed(dentry) && !IS_ROOT(dentry);
>  }

> -static inline int simple_positive(struct dentry *dentry)
> +static inline bool simple_positive(struct dentry *dentry)
>  {
>  	return d_really_is_positive(dentry) && !d_unhashed(dentry);
>  }

And these three are harmless, but completely pointless...