Re: [PATCH v3 00/10] Allocation APIs

[Danilo Krummrich <dakr@redhat.com>]

Hi all,

On 3/28/24 02:35, Wedson Almeida Filho wrote:
> From: Wedson Almeida Filho <walmeida@microsoft.com>
> 
> Revamp how we use the `alloc` crate.
> 
> We currently have a fork of the crate with changes to `Vec`; other
> changes have been upstreamed (to the Rust project). This series removes
> the fork and exposes all the functionality as extension traits.
> 
> Additionally, it also introduces allocation flag parameters to all
> functions that may result in allocations (e.g., `Box::new`, `Arc::new`,
> `Vec::push`, etc.) without the `try_` prefix -- the names are available
> because we build `alloc` with `no_global_oom_handling`.
> 
> Lastly, the series also removes our reliance on the `allocator_api`
> unstable feature.
> 
> Long term, we still want to make such functionality available in
> upstream Rust, but this allows us to make progress now and reduces our
> maintainance burden.
> 
> In summary:
> 1. Removes `alloc` fork
> 2. Removes use of `allocator_api` unstable feature
> 3. Introduces flags (e.g., GFP_KERNEL, GFP_ATOMIC) when allocating

With that series, how do we implement alternative allocators, such as
(k)vmalloc or DMA coherent?

For instance, I recently sketched up some firmware bindings we want to
use in Nova providing

fn copy<A: core::alloc::Allocator>(&self, alloc: A) -> Result<Vec<u8, 
A>> [1]

making use of Vec::try_with_capacity_in(). How would I implement
something similar now?

- Danilo

[1] 
https://gitlab.freedesktop.org/drm/nova/-/blob/topic/firmware/rust/kernel/firmware.rs?ref_type=heads#L63

> 
> ---
> 
> Changes in v3:
> - Rebased on top of the latest `rust-next` branch.
> - Updated `krealloc_aligned` to use `Flags` instead of `bindings::gfp_t`.
> - Added __GFP_ZERO to flags, as part of the previous change.
> - Avoiding temporary stack value in `Box::new_uninit`.
> - Implement `Box::new` using `Box::new_uninit` (so only one of them actually
>    allocates).
> - Added examples/tests to `VecExt` methods.
> - Fixed bug in length in `extend_from_slice`
> - Link to v2: https://lore.kernel.org/rust-for-linux/20240327023531.187880-1-wedsonaf@gmail.com/T/#t
> 
> Changes in v2:
> - Updated description of `alloc` crate.
> - Renamed vecext and boxext modules to vec_ext and box_ext.
> - Added derive directive to `AllocError`.
> - Updated safety comment in `BoxExt::new`.
> - Updated `VecExt::push` and `VecExt::extend_from_slice` to use
>    `spare_capacity_mut`
> - Added directive to not compile `destructure` and `rebuild` when `test` or
>    `testlib` are configured. Otherwise we have a warning because `push` and
>    `extend_from_slice` don't use them anymore.
> - Updated indentation in `Arc::new_uninit`
> - Moved the removal of `TryReserveError` convesion to `Error` to patch 7, where
>    usage of `TryReserveError` is actually removed.
> - Link to v1: https://lore.kernel.org/rust-for-linux/20240325195418.166013-1-wedsonaf@gmail.com/T/#t
> 
> Wedson Almeida Filho (10):
>    rust: kernel: move `allocator` module under `alloc`
>    rust: alloc: introduce the `VecExt` trait
>    kbuild: use the upstream `alloc` crate
>    rust: alloc: remove our fork of the `alloc` crate
>    rust: alloc: introduce allocation flags
>    rust: alloc: introduce the `BoxExt` trait
>    rust: alloc: update `VecExt` to take allocation flags
>    rust: sync: update `Arc` and `UniqueArc` to take allocation flags
>    rust: init: update `init` module to take allocation flags
>    rust: kernel: remove usage of `allocator_api` unstable feature
> 
>   rust/Makefile                        |   16 +-
>   rust/alloc/README.md                 |   36 -
>   rust/alloc/alloc.rs                  |  452 ----
>   rust/alloc/boxed.rs                  | 2463 -----------------
>   rust/alloc/collections/mod.rs        |  160 --
>   rust/alloc/lib.rs                    |  288 --
>   rust/alloc/raw_vec.rs                |  611 -----
>   rust/alloc/slice.rs                  |  890 -------
>   rust/alloc/vec/drain.rs              |  255 --
>   rust/alloc/vec/extract_if.rs         |  115 -
>   rust/alloc/vec/into_iter.rs          |  454 ----
>   rust/alloc/vec/is_zero.rs            |  204 --
>   rust/alloc/vec/mod.rs                | 3683 --------------------------
>   rust/alloc/vec/partial_eq.rs         |   49 -
>   rust/alloc/vec/set_len_on_drop.rs    |   35 -
>   rust/alloc/vec/spec_extend.rs        |  119 -
>   rust/bindings/bindings_helper.h      |    3 +
>   rust/kernel/alloc.rs                 |   74 +
>   rust/kernel/{ => alloc}/allocator.rs |   17 +-
>   rust/kernel/alloc/box_ext.rs         |   59 +
>   rust/kernel/alloc/vec_ext.rs         |  176 ++
>   rust/kernel/error.rs                 |   13 +-
>   rust/kernel/init.rs                  |   57 +-
>   rust/kernel/lib.rs                   |    5 +-
>   rust/kernel/prelude.rs               |    2 +
>   rust/kernel/str.rs                   |    6 +-
>   rust/kernel/sync/arc.rs              |   50 +-
>   rust/kernel/sync/condvar.rs          |    2 +-
>   rust/kernel/sync/lock/mutex.rs       |    2 +-
>   rust/kernel/sync/lock/spinlock.rs    |    2 +-
>   rust/kernel/types.rs                 |    4 +-
>   rust/kernel/workqueue.rs             |   14 +-
>   samples/rust/rust_minimal.rs         |    6 +-
>   samples/rust/rust_print.rs           |    4 +-
>   scripts/generate_rust_analyzer.py    |    2 +-
>   35 files changed, 405 insertions(+), 9923 deletions(-)
>   delete mode 100644 rust/alloc/README.md
>   delete mode 100644 rust/alloc/alloc.rs
>   delete mode 100644 rust/alloc/boxed.rs
>   delete mode 100644 rust/alloc/collections/mod.rs
>   delete mode 100644 rust/alloc/lib.rs
>   delete mode 100644 rust/alloc/raw_vec.rs
>   delete mode 100644 rust/alloc/slice.rs
>   delete mode 100644 rust/alloc/vec/drain.rs
>   delete mode 100644 rust/alloc/vec/extract_if.rs
>   delete mode 100644 rust/alloc/vec/into_iter.rs
>   delete mode 100644 rust/alloc/vec/is_zero.rs
>   delete mode 100644 rust/alloc/vec/mod.rs
>   delete mode 100644 rust/alloc/vec/partial_eq.rs
>   delete mode 100644 rust/alloc/vec/set_len_on_drop.rs
>   delete mode 100644 rust/alloc/vec/spec_extend.rs
>   create mode 100644 rust/kernel/alloc.rs
>   rename rust/kernel/{ => alloc}/allocator.rs (86%)
>   create mode 100644 rust/kernel/alloc/box_ext.rs
>   create mode 100644 rust/kernel/alloc/vec_ext.rs
> 
> 
> base-commit: 768409cff6cc89fe1194da880537a09857b6e4db