linux-kernel - Re: [RFC v3 3/3] file, epoll: Implement do_replace() and eventpoll

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Message-ID: <ZB00Cvib+jyqCR5C@casper.infradead.org>
Date:   Fri, 24 Mar 2023 05:24:26 +0000
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 Andersen <tycho@...ho.pizza>
Subject: Re: [RFC v3 3/3] file, epoll: Implement do_replace() and
 eventpoll_replace()

On Fri, Mar 24, 2023 at 05:15:26AM +0000, aloktiagi wrote:
> diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
> index 3337745d81bd..38904fce3840 100644
> --- a/include/linux/eventpoll.h
> +++ b/include/linux/eventpoll.h
> @@ -25,6 +25,8 @@ 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);
>  
> +void eventpoll_replace_file(struct file *toreplace, struct file *file);
> +
>  /*
>   * This is called from inside fs/file_table.c:__fput() to unlink files
>   * from the eventpoll interface. We need to have this facility to cleanup
> @@ -53,6 +55,22 @@ static inline void eventpoll_release(struct file *file)
>  	eventpoll_release_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
> + */
> +static inline void eventpoll_replace(struct file *toreplace, struct file *file)
> +{
> +	/*
> +	 * toreplace is the file being replaced. Install the new file for the
> +	 * existing one that is linked in the epoll interface
> +	 */
> +	eventpoll_replace_file(toreplace, file);
> +}

Why do we have both eventpoll_replace() and eventpoll_replace_file()?
They seem identical?

> diff --git a/include/linux/file.h b/include/linux/file.h
> index 39704eae83e2..80e56b2b44fb 100644
> --- a/include/linux/file.h
> +++ b/include/linux/file.h
> @@ -36,6 +36,7 @@ struct fd {
>  	struct file *file;
>  	unsigned int flags;
>  };
> +
>  #define FDPUT_FPUT       1
>  #define FDPUT_POS_UNLOCK 2
>  

You should drop this hunk of the patch.