Re: [PATCH 05/10] rust: xarray: use `xas_load` instead of `xa_load` in `Guard::load`

[Andreas Hindborg <a.hindborg@kernel.org>]

Tamir Duberstein <tamird@gmail.com> writes:

> On Wed, Dec 3, 2025 at 5:27 PM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>>
>> Replace the call to `xa_load` with `xas_load` in `Guard::load`. The
>> `xa_load` function takes the XArray lock internally, which would cause
>> a double lock since the `Guard` already holds the lock.
>
> This is not correct. `xa_load` takes and releases the RCU lock only,
> not the XArray lock.

You are right. However, we do not need to take the RCU lock either in
this case, right?

>
>> The `xas_load`
>> function operates on XArray state and assumes the lock is already held,
>> which is the correct API to use when holding a `Guard`.
>>
>> This change also removes the `#[expect(dead_code)]` annotation from
>> `XArrayState` and its constructor, as they are now in use.
>>
>> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
>> ---
>>  rust/kernel/xarray.rs | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
>> index f6e610b059625..0f69a523b72bf 100644
>> --- a/rust/kernel/xarray.rs
>> +++ b/rust/kernel/xarray.rs
>> @@ -215,8 +215,10 @@ fn load<F, U>(&self, index: usize, f: F) -> Option<U>
>>      where
>>          F: FnOnce(NonNull<c_void>) -> U,
>>      {
>> -        // SAFETY: `self.xa.xa` is always valid by the type invariant.
>> -        let ptr = unsafe { bindings::xa_load(self.xa.xa.get(), index) };
>> +        let mut state = XArrayState::new(self, index);
>> +        // SAFETY: `state.state` is always valid by the type invariant of
>> +        // `XArrayState`.
>> +        let ptr = unsafe { bindings::xas_load(&raw mut state.state) };
>
> Can this be a method on XArrayState?

OK.


Best regards,
Andreas Hindborg