From: Alice Ryhl <aliceryhl@google.com>
To: brauner@kernel.org
Cc: a.hindborg@samsung.com, alex.gaynor@gmail.com, arve@android.com,
benno.lossin@proton.me, bjorn3_gh@protonmail.com,
boqun.feng@gmail.com, cmllamas@google.com,
dan.j.williams@intel.com, dxu@dxuuu.xyz, gary@garyguo.net,
gregkh@linuxfoundation.org, joel@joelfernandes.org,
keescook@chromium.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, maco@android.com,
ojeda@kernel.org, peterz@infradead.org,
rust-for-linux@vger.kernel.org, surenb@google.com,
tglx@linutronix.de, tkjos@android.com, viro@zeniv.linux.org.uk,
wedsonaf@gmail.com, willy@infradead.org
Subject: Re: [PATCH 4/7] rust: file: add `FileDescriptorReservation`
Date: Wed, 29 Nov 2023 18:14:24 +0100 [thread overview]
Message-ID: <CAH5fLgi6n6WiueLkzvZ7ywt5hXWAJFAyseRr3O=KRAHUQ=hNrQ@mail.gmail.com> (raw)
In-Reply-To: <20231129165551.3476910-1-aliceryhl@google.com>
On Wed, Nov 29, 2023 at 5:55 PM Alice Ryhl <aliceryhl@google.com> wrote:
> >> + pub fn commit(self, file: ARef<File>) {
> >> + // SAFETY: `self.fd` was previously returned by `get_unused_fd_flags`, and `file.ptr` is
> >> + // guaranteed to have an owned ref count by its type invariants.
> >> + unsafe { bindings::fd_install(self.fd, file.0.get()) };
> >
> > Why file.0.get()? Where did that come from?
>
> This gets a raw pointer to the C type.
>
> The `.0` part is a field access. `ARef` struct is a tuple struct, so its
> fields are unnamed. However, the fields can still be accessed by index.
Oh, sorry, this is wrong. Let me try again:
This gets a raw pointer to the C type. The `.0` part accesses the
field of type `Opaque<bindings::file>` in the Rust wrapper. Recall
that File is defined like this:
pub struct File(Opaque<bindings::file>);
The above syntax defines a tuple struct, which means that the fields
are unnamed. The `.0` syntax accesses the first field of a tuple
struct [1].
The `.get()` method is from the `Opaque` struct, which returns a raw
pointer to the C type being wrapped.
Alice
[1]: https://doc.rust-lang.org/std/keyword.struct.html#:~:text=Tuple%20structs%20are%20similar%20to,with%20regular%20tuples%2C%20namely%20foo.
next prev parent reply other threads:[~2023-11-29 17:14 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-29 12:51 [PATCH 0/7] File abstractions needed by Rust Binder Alice Ryhl
2023-11-29 12:51 ` [PATCH 1/7] rust: file: add Rust abstraction for `struct file` Alice Ryhl
2023-11-29 15:13 ` Matthew Wilcox
2023-11-29 15:23 ` Peter Zijlstra
2023-11-29 17:08 ` Boqun Feng
2023-11-30 10:42 ` Peter Zijlstra
2023-11-30 15:25 ` Boqun Feng
2023-12-01 8:53 ` Peter Zijlstra
2023-12-01 9:19 ` Boqun Feng
2023-12-01 9:40 ` Peter Zijlstra
2023-12-01 10:36 ` Boqun Feng
2023-12-01 11:05 ` Peter Zijlstra
2023-12-01 9:00 ` Peter Zijlstra
2023-12-01 9:52 ` Boqun Feng
2023-11-29 16:42 ` Alice Ryhl
2023-11-29 16:45 ` Peter Zijlstra
2023-11-30 15:02 ` Benno Lossin
2023-11-29 17:06 ` Christian Brauner
2023-11-29 21:27 ` Alice Ryhl
2023-11-29 23:17 ` Benno Lossin
2023-11-30 10:48 ` Christian Brauner
2023-11-30 12:10 ` Alice Ryhl
2023-11-30 12:36 ` Christian Brauner
2023-11-30 14:53 ` Benno Lossin
2023-11-30 14:59 ` Greg Kroah-Hartman
2023-11-30 15:46 ` Benno Lossin
2023-11-30 15:56 ` Greg Kroah-Hartman
2023-11-30 15:58 ` Theodore Ts'o
2023-11-30 16:12 ` Benno Lossin
2023-12-01 1:16 ` Theodore Ts'o
2023-12-01 12:11 ` David Laight
2023-12-01 12:27 ` Alice Ryhl
2023-12-01 15:04 ` Theodore Ts'o
2023-12-01 15:14 ` Benno Lossin
2023-12-01 17:25 ` David Laight
2023-12-01 17:37 ` Benno Lossin
2023-11-29 12:51 ` [PATCH 2/7] rust: cred: add Rust abstraction for `struct cred` Alice Ryhl
2023-11-30 16:17 ` Benno Lossin
2023-12-01 9:06 ` Alice Ryhl
2023-12-01 10:27 ` Christian Brauner
2023-12-04 15:42 ` Alice Ryhl
2023-11-29 13:11 ` [PATCH 3/7] rust: security: add abstraction for secctx Alice Ryhl
2023-11-30 16:26 ` Benno Lossin
2023-12-01 10:48 ` Alice Ryhl
2023-12-02 10:03 ` Benno Lossin
2023-11-29 13:11 ` [PATCH 4/7] rust: file: add `FileDescriptorReservation` Alice Ryhl
2023-11-29 16:14 ` Christian Brauner
2023-11-29 16:55 ` Alice Ryhl
2023-11-29 17:14 ` Alice Ryhl [this message]
2023-11-30 9:12 ` Christian Brauner
2023-11-30 9:23 ` Alice Ryhl
2023-11-30 9:09 ` Christian Brauner
2023-11-30 9:17 ` Alice Ryhl
2023-11-30 10:51 ` Christian Brauner
2023-11-30 11:54 ` Alice Ryhl
2023-11-30 12:17 ` Benno Lossin
2023-11-30 12:33 ` Christian Brauner
2023-11-30 16:40 ` Benno Lossin
2023-12-01 11:32 ` Alice Ryhl
2023-11-29 13:12 ` [PATCH 5/7] rust: file: add `Kuid` wrapper Alice Ryhl
2023-11-29 16:28 ` Christian Brauner
2023-11-29 16:48 ` Peter Zijlstra
2023-11-30 12:46 ` Christian Brauner
2023-12-06 19:59 ` Kent Overstreet
2023-12-08 16:26 ` Peter Zijlstra
2023-12-08 19:58 ` Kent Overstreet
2023-12-08 5:28 ` comex
2023-12-08 16:19 ` Miguel Ojeda
2023-12-08 17:08 ` Nick Desaulniers
2023-12-08 17:37 ` Miguel Ojeda
2023-12-08 17:43 ` Boqun Feng
2023-12-08 20:43 ` Matthew Wilcox
2023-12-09 7:24 ` comex
2023-11-30 9:36 ` Alice Ryhl
2023-11-30 10:52 ` Christian Brauner
2023-11-30 10:36 ` Peter Zijlstra
2023-12-06 20:02 ` Kent Overstreet
2023-12-07 7:18 ` Greg Kroah-Hartman
2023-12-07 7:46 ` Kent Overstreet
2023-11-30 16:48 ` Benno Lossin
2023-11-29 13:12 ` [PATCH 6/7] rust: file: add `DeferredFdCloser` Alice Ryhl
2023-11-30 17:12 ` Benno Lossin
2023-12-01 11:35 ` Alice Ryhl
2023-12-02 10:16 ` Benno Lossin
2023-12-05 14:43 ` Alice Ryhl
2023-12-05 18:16 ` Alice Ryhl
2023-11-29 13:12 ` [PATCH 7/7] rust: file: add abstraction for `poll_table` Alice Ryhl
2023-11-30 17:42 ` Benno Lossin
2023-12-01 11:47 ` Alice Ryhl
2023-11-30 22:39 ` Boqun Feng
2023-12-01 11:50 ` Alice Ryhl
2023-11-30 22:50 ` Boqun Feng
2023-11-29 16:31 ` [PATCH 0/7] File abstractions needed by Rust Binder Christian Brauner
2023-11-29 16:48 ` Miguel Ojeda
2023-12-06 20:05 ` Kent Overstreet
2023-12-08 16:59 ` Miguel Ojeda
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