linux-kernel - Re: [RFC v6 1/2] epoll: Implement eventpoll_replace

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Message-ID: <ZGzATlGu7mh6EFUi@casper.infradead.org>
Date:   Tue, 23 May 2023 14:31:58 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     aloktiagi <aloktiagi@...il.com>
Cc:     viro@...iv.linux.org.uk, brauner@...nel.org,
        David.Laight@...lab.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, keescook@...omium.org,
        hch@...radead.org, tycho@...ho.pizza
Subject: Re: [RFC v6 1/2] epoll: Implement eventpoll_replace_file()

On Tue, May 23, 2023 at 06:58:01AM +0000, aloktiagi wrote:
> +/*
> + * This is called from eventpoll_replace() to replace a linked file in the epoll
> + * interface with a new file received from another process. This is useful in
> + * cases where a process is trying to install a new file for an existing one
> + * that is linked in the epoll interface
> + */
> +int eventpoll_replace_file(struct file *toreplace, struct file *file, int tfd)

Functions do not control where they are called from.  Just take that
clause out:

/*
 * Replace a linked file in the epoll interface with a new file received
 * from another process. This allows a process to
 * install a new file for an existing one that is linked in the epoll
 * interface
 */

But, erm, aren't those two sentences basically saying the same thing?
So simplify again:

/*
 * Replace a linked file in the epoll interface with a new file
 */

> diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
> index 3337745d81bd..2a6c8f52f272 100644
> --- a/include/linux/eventpoll.h
> +++ b/include/linux/eventpoll.h
> @@ -25,6 +25,14 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long t
>  /* Used to release the epoll bits inside the "struct file" */
>  void eventpoll_release_file(struct file *file);
>  
> +/*
> + * This is called from fs/file.c:do_replace() to replace a linked file in the
> + * epoll interface with a new file received from another process. This is useful
> + * in cases where a process is trying to install a new file for an existing one
> + * that is linked in the epoll interface
> + */
> +int eventpoll_replace_file(struct file *toreplace, struct file *file, int tfd);

No need to repeat the comment again.  Just delete it here.