linux-kernel - Re: [PATCH v5 00/26] Generic `Allocator` support for Rust

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Message-ID: <e428c15c-f11b-4bbd-9cef-1ad252b206bb@kernel.org>
Date: Wed, 14 Aug 2024 22:53:41 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Boqun Feng <boqun.feng@...il.com>
Cc: ojeda@...nel.org, alex.gaynor@...il.com, wedsonaf@...il.com,
 gary@...yguo.net, bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
 a.hindborg@...sung.com, aliceryhl@...gle.com, akpm@...ux-foundation.org,
 daniel.almeida@...labora.com, faith.ekstrand@...labora.com,
 boris.brezillon@...labora.com, lina@...hilina.net, mcanal@...lia.com,
 zhiw@...dia.com, cjia@...dia.com, jhubbard@...dia.com, airlied@...hat.com,
 ajanulgu@...hat.com, lyude@...hat.com, linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v5 00/26] Generic `Allocator` support for Rust

On 8/14/24 9:32 PM, Boqun Feng wrote:
> Hi Danilo,
> 
> On Mon, Aug 12, 2024 at 08:22:46PM +0200, Danilo Krummrich wrote:
>> Hi,
>>
>> This patch series adds generic kernel allocator support for Rust, which so far
>> is limited to `kmalloc` allocations.
>>
>> In order to abstain from (re-)adding unstable Rust features to the kernel, this
>> patch series does not extend the `Allocator` trait from Rust's `alloc` crate,
>> nor does it extend the `BoxExt` and `VecExt` extensions.
>>
>> Instead, this series introduces a kernel specific `Allocator` trait, which is
>> implemented by the `Kmalloc`, `Vmalloc` and `KVmalloc` allocators, also
>> implemented in the context of this series.
>>
>> As a consequence we need our own kernel `Box<T, A>` and `Vec<T, A>` types.
>> Additionally, this series adds the following type aliases:
>>
>> ```
>> pub type KBox<T> = Box<T, Kmalloc>;
>> pub type VBox<T> = Box<T, Vmalloc>;
>> pub type KVBox<T> = Box<T, KVmalloc>;
>>
>>
>> pub type KVec<T> = Vec<T, Kmalloc>;
>> pub type VVec<T> = Vec<T, Vmalloc>;
>> pub type KVVec<T> = Vec<T, KVmalloc>;
>> ```
>>
>> With that, we can start using the kernel `Box` and `Vec` types throughout the
>> tree and remove the now obolete extensions `BoxExt` and `VecExt`.
>>
>> For a final cleanup, this series removes the last minor dependencies to Rust's
>> `alloc` crate and removes it from the entire kernel build.
>>
>> The series ensures not to break the `rusttest` make target by implementing the
>> `allocator_test` module providing a stub implementation for all kernel
>> `Allocator`s.
>>
>> This patch series passes all KUnit tests, including the ones added by this
>> series. Additionally, the tests were run with `kmemleak` and `KASAN` enabled,
>> without any issues.
>>
>> This series is based on [1], which hit -mm/mm-unstable, and is also available
>> in [2].
>>
>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=mm/krealloc
>> [2] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=rust/mm
>>
>> Changes in v5:
>>   - (safety) comment / documentation fixes suggested by Alice, Benno and Gary
>>   - remove `Unique<T>` and implement `Send` and `Sync` for `Box` and `Vec`
>>   - use `KMALLOC_MAX_SIZE` for `KVmalloc` test and add a `Kmalloc` test that
>>     expects to fail for `KMALLOC_MAX_SIZE`
>>   - create use constants `KREALLOC`, `VREALLOC` and `KVREALLOC` for
>>     `ReallocFuncs`
>>   - drop `Box::drop_contents` for now, will add it again, once I actually rebase
>>     on the original patch that introduces it
> 
> I'm trying to put your series on rust-dev, but I hit a few conflicts due
> to the conflict with `Box::drop_contents`, which has been in rust-dev
> for a while. And the conflict is not that trivial for me to resolve.
> So just a head-up, that's a requirement for me to put it on rust-dev for
> more tests from my end ;-)

I'll rebase later on and send you a branch.

> 
> Regards,
> Boqun
> 
>>   - improve usage of `size_of_val` in `Box`
>>   - move `InPlaceInit` and `ForeignOwnable` impls into kbox.rs
>>   - fix missing `Box` conversions in rnull.rs
>>   - reworked `Cmalloc` to keep track of the size of memory allocations itself
>>   - remove `GlobalAlloc` together with the `alloc` crate to avoid a linker error
>>   - remove `alloc` from scripts/generate_rust_analyzer.py
>>
> [...]
>