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From:   Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date:   Thu, 20 Jul 2023 20:22:34 +0200
Message-ID: <CANiq72=44YaQ--QV7+H5cQUY4o9i6hbz3OD_F_u0JGV4PzV-OQ@mail.gmail.com>
Subject: Re: [RFC PATCH v1 5/5] rust: file: add `DeferredFdCloser`
To:     Alice Ryhl <aliceryhl@google.com>
Cc:     rust-for-linux@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Miguel Ojeda <ojeda@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>,
        Benno Lossin <benno.lossin@proton.me>,
        linux-kernel@vger.kernel.org, patches@lists.linux.dev
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Hi Alice,

A quick comment on referencing commits:

On Thu, Jul 20, 2023 at 5:29=E2=80=AFPM Alice Ryhl <aliceryhl@google.com> w=
rote:
>
> See comments on `binder_do_fd_close` and commit `80cd795630d65` for
> motivation.

The convention is to write these commit references like this:

    commit 80cd795630d6 ("binder: fix use-after-free due to
ksys_close() during fdget()")

I recommend generating them with a Git pretty format -- see the config
in the bottom part of the section at
https://docs.kernel.org/process/submitting-patches.html#describe-your-chang=
es.

Also, given it is a kernel convention, please avoid the Markdown
backticks in this case.

> +/// See comments on `binder_do_fd_close` and commit `80cd795630d65`.

Same here, i.e. in comments and documentation too (and emails too,
especially if not referenced elsewhere).

While I am at it, a few other notes below too I noticed:

> +    /// Create a new `DeferredFdCloser`.

[`DeferredFdCloser`]

> +    /// Schedule a task work that closes the file descriptor when this t=
ask returns to userspace.
> +    pub fn close_fd(mut self, fd: u32) {
> +        let file =3D unsafe { bindings::close_fd_get_file(fd) };
> +        if !file.is_null() {

Please use the early return style here, if possible, to unindent all this.

> +            // SAFETY: Since DeferredFdCloserInner is `#[repr(C)]`, cast=
ing the pointers gives a

`DeferredFdCloserInner`

> +            // Note: fl_owner_t is currently a void pointer.

`fl_owner_t`

> +            // SAFETY: The `inner` pointer is compatible with the `do_cl=
ose_fd` method.
> +            //
> +            // The call to `task_work_add` can't fail, because we are sc=
heduling the task work to
> +            // the current task.
> +            unsafe {
> +                bindings::init_task_work(inner, Some(Self::do_close_fd))=
;
> +                bindings::task_work_add(current, inner, bindings::task_w=
ork_notify_mode_TWA_RESUME);
> +            }

Should this block be split?

>  /// Represents the EBADF error code.
>  ///
>  /// Used for methods that can only fail with EBADF.

Doclink them if possible; otherwise `EBADF`.

Cheers,
Miguel