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AJvYcCUsw5UqHaFd6uAaMx5B9wOQAr7grYTzEuA8uNAi6GRLl106C+LWWQkdkAL9yfKq5UCPvJ6IUups760CknvXxPvhBh8= X-Gm-Message-State: AOJu0YyRDPkur0J5id820mtmxr02yJ8RTvZklOXPkNGF/aMMX9praIV8 MvcWVsDhKyskJSAfBtg4aGt24+X+mNqJeZupxG4dDZ8bnxaA/Sv7TGYLH/Ed/kYbEDpJIH78QT7 9ZDGcoTj/ORvyt7j9GF7g5vciXRw6XWGKztE4 X-Google-Smtp-Source: AGHT+IFrmL3U1S+rpzBOdS5HfRHkuyTVNTg4EqoC10UJXSwLurGP5QVOWdVYxkQVIjwptFuwedEGKyhyn45M8GLcKU0= X-Received: by 2002:a5d:59a5:0:b0:367:9903:a91 with SMTP id ffacd0b85a97d-37177744793mr1608078f8f.11.1723624960494; Wed, 14 Aug 2024 01:42:40 -0700 (PDT) MIME-Version: 1.0 References: <20240812182355.11641-1-dakr@kernel.org> <20240812182355.11641-14-dakr@kernel.org> In-Reply-To: <20240812182355.11641-14-dakr@kernel.org> From: Alice Ryhl Date: Wed, 14 Aug 2024 10:42:28 +0200 Message-ID: Subject: Re: [PATCH v5 13/26] rust: alloc: implement kernel `Vec` type To: Danilo Krummrich Cc: ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, akpm@linux-foundation.org, daniel.almeida@collabora.com, faith.ekstrand@collabora.com, boris.brezillon@collabora.com, lina@asahilina.net, mcanal@igalia.com, zhiw@nvidia.com, cjia@nvidia.com, jhubbard@nvidia.com, airlied@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 6161A18000A X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: jpcbxota4ozy1d7o3u8sfoejr1hc6ybd X-HE-Tag: 1723624962-891024 X-HE-Meta: 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 2V4rdFsQ AEfXecdFPS3Eo+2qUaHLBfz04v19T25w6/yvGRGaqz5WG0ZqmifV+PMYR+0EBejsl0XKtMUm1rYtHbQzKoO83B99E6wtOAeLw9e93sQYiX3UTYMjVZeZ6GEGl8Fkz7XSjQUCEsoQ3U5nsFyr+s1NxuDHkQAV0BM5SbKAW0sezHyIYD54udr4POzqCpT+oReK45/MMrdvYx3f2N8uaLo5hYBCKOhmfgnlhF9tPXuZFhB7UuflkiKcpnKMvOwUL7A6be3Bfruz4KrbOVcgmeql2t6CJpG78/KGuQxDL4MYmplRLJgVv5PIbFnNzfg1OJYkwcRzcHFGfiZXcvPg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.386743, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 12, 2024 at 8:25=E2=80=AFPM Danilo Krummrich = wrote: > > `Vec` provides a contiguous growable array type (such as `Vec`) with > contents allocated with the kernel's allocators (e.g. `Kmalloc`, > `Vmalloc` or `KVmalloc`). > > In contrast to Rust's `Vec` type, the kernel `Vec` type considers the > kernel's GFP flags for all appropriate functions, always reports > allocation failures through `Result<_, AllocError>` and remains > independent from unstable features. > > Signed-off-by: Danilo Krummrich > [...] > +impl Box<[T; N], A> > +where > + A: Allocator, > +{ > + /// Convert a `Box<[T, N], A>` to a `Vec`. > + pub fn into_vec(b: Self) -> Vec { Nit: I would probably make this a From impl. > +#[macro_export] > +macro_rules! kvec { > + () =3D> ( > + { > + $crate::alloc::KVec::new() > + } > + ); > + ($elem:expr; $n:expr) =3D> ( > + { > + $crate::alloc::KVec::from_elem($elem, $n, GFP_KERNEL) > + } > + ); > + ($($x:expr),+ $(,)?) =3D> ( > + { > + match $crate::alloc::KBox::new([$($x),+], GFP_KERNEL) { > + Ok(b) =3D> Ok($crate::alloc::KBox::into_vec(b)), > + Err(e) =3D> Err(e), Hmm. This currently generates code that: 1. Creates the array. 2. Allocates the memory. 3. Moves the array into the box. Whereas the stdlib macro swaps step 1 and 2. You can do the same by utilizing new_uninit. A sketch: match KBox::<[_; _]>::new_uninit(GFP_KERNEL) { Ok(b) =3D> Ok(KVec::from(KBox::write(b, [$($x),+]))), Err(e) =3D> Err(e), } > +// SAFETY: `Vec` is `Send` if `T` is `Send` because the data referenced = by `self.ptr` is unaliased. > +unsafe impl Send for Vec > +where > + T: Send, > + A: Allocator, > +{ > +} > + > +// SAFETY: `Vec` is `Sync` if `T` is `Sync` because the data referenced = by `self.ptr` is unaliased. > +unsafe impl Sync for Vec > +where > + T: Send, > + A: Allocator, Same comment as Box. Ditto about "unaliased". Needs `T: Sync` instead. > +impl Vec { > + /// Extend the vector by `n` clones of value. > + pub fn extend_with(&mut self, n: usize, value: T, flags: Flags) -> R= esult<(), AllocError> { > + self.reserve(n, flags)?; > + > + let spare =3D self.spare_capacity_mut(); > + > + for item in spare.iter_mut().take(n - 1) { You need to handle `n =3D=3D 0` here. Alice