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Date: Wed, 3 Apr 2024 13:01:46 +0200
From: Jan Kara <jack@suse.cz>
To: linke li <lilinke99@qq.com>
Cc: xujianhao01@gmail.com, Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fs/dcache: Re-use value stored to dentry->d_flags
 instead of re-reading
Message-ID: <20240403110146.axoxzqr4zwoeyyas@quack3>
References: <tencent_5E187BD0A61BA28605E85405F15228254D0A@qq.com>
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In-Reply-To: <tencent_5E187BD0A61BA28605E85405F15228254D0A@qq.com>

On Wed 03-04-24 10:10:08, linke li wrote:
> Currently, the __d_clear_type_and_inode() writes the value flags to
> dentry->d_flags, then immediately re-reads it in order to use it in a if
> statement. This re-read is useless because no other update to 
> dentry->d_flags can occur at this point.
> 
> This commit therefore re-use flags in the if statement instead of
> re-reading dentry->d_flags.
> 
> Signed-off-by: linke li <lilinke99@qq.com>

Indeed, this seems pointless and actually a bit confusing. Feel free to
add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/dcache.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/dcache.c b/fs/dcache.c
> index b813528fb147..79da415d7995 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -355,7 +355,7 @@ static inline void __d_clear_type_and_inode(struct dentry *dentry)
>  	flags &= ~DCACHE_ENTRY_TYPE;
>  	WRITE_ONCE(dentry->d_flags, flags);
>  	dentry->d_inode = NULL;
> -	if (dentry->d_flags & DCACHE_LRU_LIST)
> +	if (flags & DCACHE_LRU_LIST)
>  		this_cpu_inc(nr_dentry_negative);
>  }
>  
> -- 
> 2.39.3 (Apple Git-146)
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR