Re: [PATCH v4] rust: xarray: Add an abstraction for XArray

[Boqun Feng <boqun.feng@gmail.com>]

On Sun, Nov 26, 2023 at 10:01:40AM -0300, Maíra Canal wrote:
> From: Asahi Lina <lina@asahilina.net>
> 
> The XArray is an abstract data type which behaves like a very large
> array of pointers. Add a Rust abstraction for this data type.
> 
> The initial implementation uses explicit locking on get operations and
> returns a guard which blocks mutation, ensuring that the referenced
> object remains alive. To avoid excessive serialization, users are
> expected to use an inner type that can be efficiently cloned (such as
> Arc<T>), and eagerly clone and drop the guard to unblock other users
> after a lookup.
> 
> Future variants may support using RCU instead to avoid mutex locking.
> 
> This abstraction also introduces a reservation mechanism, which can be
> used by alloc-capable XArrays to reserve a free slot without immediately
> filling it, and then do so at a later time. If the reservation is
> dropped without being filled, the slot is freed again for other users,
> which eliminates the need for explicit cleanup code.
> 
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> Signed-off-by: Maíra Canal <mcanal@igalia.com>
> ---
> 
> This abstraction is part of the set of dependencies I need to upstream
> rustgem, a virtual GEM provider driver in the DRM [1]. Also, this
> abstraction will be useful for the upstreaming process of the drm/asahi
> driver.
> 
> This patch was authored by Asahi Lina and I rebased on top of rust-next,
> fixing small conflicts. I'll try to take care of possible iterations
> that this patch might have and I'll try to address the feedback.
> 

Thank you! Among anything else, since we now have the ability to convert
a Rust code example in doc to actual tests, do you mind add a few
```rust ``` blocks in the comments of the functions to 1) demonstrate
the usage and 2) serve as unit tests. Below is the command I run for
testing:

	./tools/testing/kunit/kunit.py run --make_options LLVM=1 --arch x86_64 --kconfig_add CONFIG_RUST=y	

Regards,
Boqun

> Best Regards,
> - Maíra
> 
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