linux-kernel - Re: [PATCH bpf-next] bpf: remove unnecessary loop in task_file_seq_get

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Message-ID: <ZocaRENGH-HFLo4p@krava>
Date: Thu, 4 Jul 2024 23:55:16 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Yonghong Song <yonghong.song@...ux.dev>,
	Christian Brauner <brauner@...nel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH bpf-next] bpf: remove unnecessary loop in
 task_file_seq_get_next()

On Thu, Jul 04, 2024 at 10:19:19AM -0500, Dan Carpenter wrote:
> After commit 0ede61d8589c ("file: convert to SLAB_TYPESAFE_BY_RCU") this
> loop always iterates exactly one time.  Delete the for statement and pull
> the code in a tab.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>

lgtm

Acked-by: Jiri Olsa <jolsa@...nel.org>

jirka

> ---
>  kernel/bpf/task_iter.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
> index ec4e97c61eef..02aa9db8d796 100644
> --- a/kernel/bpf/task_iter.c
> +++ b/kernel/bpf/task_iter.c
> @@ -261,6 +261,7 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info)
>  	u32 saved_tid = info->tid;
>  	struct task_struct *curr_task;
>  	unsigned int curr_fd = info->fd;
> +	struct file *f;
>  
>  	/* If this function returns a non-NULL file object,
>  	 * it held a reference to the task/file.
> @@ -286,12 +287,8 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info)
>  	}
>  
>  	rcu_read_lock();
> -	for (;; curr_fd++) {
> -		struct file *f;
> -		f = task_lookup_next_fdget_rcu(curr_task, &curr_fd);
> -		if (!f)
> -			break;
> -
> +	f = task_lookup_next_fdget_rcu(curr_task, &curr_fd);
> +	if (f) {
>  		/* set info->fd */
>  		info->fd = curr_fd;
>  		rcu_read_unlock();
> -- 
> 2.43.0
>