linux-kernel - Re: [PATCH] fs/ext4: replace ternary operator with min() and max()

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Date:   Tue, 9 Aug 2022 09:52:25 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     Jiangshan Yi <13667453960@....com>
Cc:     tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jiangshan Yi <yijiangshan@...inos.cn>
Subject: Re: [PATCH] fs/ext4: replace ternary operator with min() and max()

On Tue, Aug 09, 2022 at 02:10:31PM +0800, Jiangshan Yi wrote:
> From: Jiangshan Yi <yijiangshan@...inos.cn>
> 
> Fix the following coccicheck warning:
> 
> fs/ext4/extents.c:2631: WARNING opportunity for max().
> fs/ext4/extents.c:2632: WARNING opportunity for min().
> 
> min() and max() macro is defined in include/linux/minmax.h. It avoids
> multiple evaluations of the arguments when non-constant and performs
> strict type-checking.
> 
> Signed-off-by: Jiangshan Yi <yijiangshan@...inos.cn>
> ---
>  fs/ext4/extents.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index c148bb97b527..3a74d0961024 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -2628,9 +2628,8 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
>  			  unwritten, ex_ee_len);
>  		path[depth].p_ext = ex;
>  
> -		a = ex_ee_block > start ? ex_ee_block : start;
> -		b = ex_ee_block+ex_ee_len - 1 < end ?
> -			ex_ee_block+ex_ee_len - 1 : end;
> +		a = max(ex_ee_block, start);
> +		b = min(ex_ee_block+ex_ee_len - 1, end);

You could add spaces around the + sign, but other than that the patch
looks good. Thanks!

Reviewed-by: Lukas Czerner <lczerner@...hat.com>

Also note that a quick grep on ext4 tree reveals that there are likely
many more opportunities for using min/max.

-Lukas

>  
>  		ext_debug(inode, "  border %u:%u\n", a, b);
>  
> -- 
> 2.25.1
> 
> 
> No virus found
> 		Checked by Hillstone Network AntiVirus
>