Re: [PATCH v4 02/11] rust: mm: add `task_size` helper

[Alice Ryhl <aliceryhl@google.com>]

On Thu, Oct 22, 2026 at 04:53:07PM -0700, Deborah Brouwer wrote:
> On Tue, Oct 20, 2026 at 04:25:19PM +0800, Ke Sun wrote:
> > From: Alvin Sun <alvin.sun@linux.dev>
> 
> I was testing Tyr's auto allocation for the user va range,
> and was surprised to see that mm.task_size() is always returning 0.
> It seems like it should work since it uses the task_size from
> struct mm_struct, but it doesn't, at least for me. 
> 
> If you look at tyr-dev, I think it would be better to use Sami's approach:
>   428d71932b6f rust: task: add task_size()
> 
> Sami creates a task_size() method for CurrentTask which is our equivalent
> to the `current` global and then you can see that task_size becomes much
> more clearly the equivalent of "TASK_SIZE_OF" used by panthor.
> 
> This approach also correctly returns a user va range when Tyr has to
> assign it in my tests, so let's switch over.

+1 to switching to CurrentTask::task_size(&self) backed by a C helper
calling TASK_SIZE_OF(current). Please also include `<linux/mm.h>` in
`rust/helpers/task.c`, as on some architectures (e.g. riscv) `TASK_SIZE` is
defined in `<asm/pgtable.h>` rather than `<linux/sched/task.h>`.

Alice