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Date:   Sat, 21 Nov 2020 21:19:33 +0300
From:   Cyrill Gorcunov <gorcunov@gmail.com>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        criu@openvz.org, bpf@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Miklos Szeredi <miklos@szeredi.hu>,
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        "J. Bruce Fields" <bfields@fieldses.org>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
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        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>
Subject: Re: [PATCH v2 11/24] file: Implement task_lookup_fd_rcu
Message-ID: <20201121181933.GH875895@grain>
References: <87r1on1v62.fsf@x220.int.ebiederm.org>
 <20201120231441.29911-11-ebiederm@xmission.com>
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On Fri, Nov 20, 2020 at 05:14:28PM -0600, Eric W. Biederman wrote:
> 
> diff --git a/fs/file.c b/fs/file.c
> index 5861c4f89419..6448523ca29e 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -865,6 +865,21 @@ struct file *fget_task(struct task_struct *task, unsigned int fd)
>  	return file;
>  }
>  
> +struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)
> +{
> +	/* Must be called with rcu_read_lock held */

Eric, maybe worth to have something like

	RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
			 "suspicious task_lookup_fd_rcu() usage");

here?