linux-kernel - Re: [PATCH v4 2/2] rust: zpool: add abstraction for zpool drivers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <DFA3B588-3650-42DA-8875-7AB7D20A2BCA@konsulko.se>
Date: Wed, 27 Aug 2025 16:24:08 +0200
From: Vitaly Wool <vitaly.wool@...sulko.se>
To: Benno Lossin <lossin@...nel.org>
Cc: rust-for-linux <rust-for-linux@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>,
 Uladzislau Rezki <urezki@...il.com>,
 Danilo Krummrich <dakr@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>,
 Vlastimil Babka <vbabka@...e.cz>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 "Liam R . Howlett" <Liam.Howlett@...cle.com>,
 Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>,
 Gary Guo <gary@...yguo.net>,
 Bjorn Roy Baron <bjorn3_gh@...tonmail.com>,
 Andreas Hindborg <a.hindborg@...nel.org>,
 Trevor Gross <tmgross@...ch.edu>,
 Johannes Weiner <hannes@...xchg.org>,
 Yosry Ahmed <yosry.ahmed@...ux.dev>,
 Nhat Pham <nphamcs@...il.com>,
 linux-mm@...ck.org
Subject: Re: [PATCH v4 2/2] rust: zpool: add abstraction for zpool drivers

> On Aug 26, 2025, at 7:02 PM, Benno Lossin <lossin@...nel.org> wrote:
> 
> On Sat Aug 23, 2025 at 3:05 PM CEST, Vitaly Wool wrote:
>> +pub trait ZpoolDriver {
>> +    /// Opaque Rust representation of `struct zpool`.
>> +    type Pool: ForeignOwnable;
> 
> I think this is the same question that Danilo asked a few versions ago,
> but why do we need this? Why can't we just use `Self` instead?

It’s convenient to use it in the backend implementation, like in the toy example supplied in the documentation part:

+/// struct MyZpool {
+///     name: &'static CStr,
+///     bytes_used: AtomicU64,
+/// }
…
+/// impl ZpoolDriver for MyZpoolDriver {
+///     type Pool = KBox<MyZpool>;

Does that make sense?

> 
>> +
>> +    /// Create a pool.
>> +    fn create(name: &'static CStr, gfp: Flags) -> Result<Self::Pool>;
>> +
>> +    /// Destroy the pool.
>> +    fn destroy(pool: Self::Pool);
> 
> This should just be done via the normal `Drop` trait?

Let me check if I’m getting you right here. I take what you are suggesting is that we require that Pool implements Drop trait and then just do something like:

    extern "C" fn destroy_(pool: *mut c_void) {
        // SAFETY: The pointer originates from an `into_foreign` call.
        unsafe { drop(T::Pool::from_foreign(pool)) }
    }

Is that understanding correct?

~Vitaly

> 
> ---
> Cheers,
> Benno
> 
>> +
>> +    /// Allocate an object of size `size` bytes from `pool`, with the allocation flags `gfp` and
>> +    /// preferred NUMA node `nid`. If the allocation is successful, an opaque handle is returned.
>> +    fn malloc(
>> +        pool: <Self::Pool as ForeignOwnable>::BorrowedMut<'_>,
>> +        size: usize,
>> +        gfp: Flags,
>> +        nid: NumaNode,
>> +    ) -> Result<usize>;
>