linux-kernel - Re: [PATCH v2 2/7] rust: cred: add Rust abstraction for `struct cred`

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Date:   Mon, 11 Dec 2023 15:34:29 +0000
From:   Alice Ryhl <aliceryhl@...gle.com>
To:     boqun.feng@...il.com
Cc:     a.hindborg@...sung.com, alex.gaynor@...il.com,
        aliceryhl@...gle.com, arve@...roid.com, benno.lossin@...ton.me,
        bjorn3_gh@...tonmail.com, brauner@...nel.org, cmllamas@...gle.com,
        dan.j.williams@...el.com, dxu@...uu.xyz, gary@...yguo.net,
        gregkh@...uxfoundation.org, joel@...lfernandes.org,
        keescook@...omium.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, maco@...roid.com, ojeda@...nel.org,
        peterz@...radead.org, rust-for-linux@...r.kernel.org,
        surenb@...gle.com, tglx@...utronix.de, tkjos@...roid.com,
        viro@...iv.linux.org.uk, wedsonaf@...il.com, willy@...radead.org
Subject: Re: [PATCH v2 2/7] rust: cred: add Rust abstraction for `struct cred`

Boqun Feng <boqun.feng@...il.com> writes:
> On Wed, Dec 06, 2023 at 11:59:47AM +0000, Alice Ryhl wrote:
> [...]
> > @@ -151,6 +152,21 @@ pub fn as_ptr(&self) -> *mut bindings::file {
> >          self.0.get()
> >      }
> >  
> > +    /// Returns the credentials of the task that originally opened the file.
> > +    pub fn cred(&self) -> &Credential {
> 
> I wonder whether it would be helpful if we use explicit lifetime here:
> 
>     pub fn cred<'file>(&'file self) -> &'file Credential
> 
> It might be easier for people to get. For example, the lifetime of the
> returned Credential reference is constrainted by 'file, the lifetime of
> the file reference.
> 
> But yes, maybe need to hear others' feedback first.
> 
> Regards,
> Boqun

That would trigger a compiler warning because the lifetime is
unnecessary.

The safety comment explains what the signature means. I think that
should be enough.

Alice