Re: [PATCH v3 3/3] rust: alloc: move `NumaNode` to the `numa` module

[Andreas Hindborg]

"Gary Guo" <gary@xxxxxxxxxxx> writes:

> On Tue Sep 29, 2026 at 6:56 PM BST, Andreas Hindborg wrote:
>> `NumaNode` identifies a NUMA node and is not specific to the allocator API.
>> Move it from the `alloc` module to the `numa` module so that NUMA related
>> items live together.
>>
>> No functional change.
>>
>> Suggested-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
>> Link: https://lore.kernel.org/all/aiZvKPFCkqJUsP0a@xxxxxxxxxx/
>> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
>> ---
>>  rust/kernel/alloc.rs           | 30 ++++--------------------------
>>  rust/kernel/alloc/allocator.rs |  6 +++---
>>  rust/kernel/alloc/kbox.rs      |  4 ++--
>>  rust/kernel/alloc/kvec.rs      |  4 ++--
>>  rust/kernel/numa.rs            | 35 ++++++++++++++++++++++++++++++++++-
>>  5 files changed, 45 insertions(+), 34 deletions(-)
>>
>> diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
>> index 21067bde6860..9daddf540e7d 100644
>> --- a/rust/kernel/alloc.rs
>> +++ b/rust/kernel/alloc.rs
>> @@ -22,7 +22,10 @@
>>  #[derive(Copy, Clone, PartialEq, Eq, Debug)]
>>  pub struct AllocError;
>>  
>> -use crate::prelude::*;
>> +use crate::{
>> +    numa::NumaNode,
>> +    prelude::*, //
>> +};
>>  
>>  use core::{
>>      alloc::Layout,
>> @@ -114,31 +117,6 @@ pub mod flags {
>>      pub const __GFP_NOWARN: Flags = Flags(bindings::__GFP_NOWARN);
>>  }
>>  
>> -/// Non Uniform Memory Access (NUMA) node identifier.
>> -#[derive(Clone, Copy, PartialEq)]
>> -pub struct NumaNode(i32);
>> -
>> -impl NumaNode {
>> -    /// Create a new NUMA node identifier (non-negative integer).
>> -    ///
>> -    /// Returns [`EINVAL`] if a negative id or an id exceeding [`bindings::MAX_NUMNODES`] is
>> -    /// specified.
>> -    pub fn new(node: i32) -> Result<Self> {
>> -        // MAX_NUMNODES never exceeds 2**10 because NODES_SHIFT is 0..10.
>> -        if node < 0 || node >= bindings::MAX_NUMNODES as i32 {
>> -            return Err(EINVAL);
>> -        }
>> -        Ok(Self(node))
>> -    }
>> -}
>> -
>> -/// Specify necessary constant to pass the information to Allocator that the caller doesn't care
>> -/// about the NUMA node to allocate memory from.
>> -impl NumaNode {
>> -    /// No node preference.
>> -    pub const NO_NODE: NumaNode = NumaNode(bindings::NUMA_NO_NODE);
>> -}
>> -
>>  /// The kernel's [`Allocator`] trait.
>>  ///
>>  /// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffers described
>> diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
>> index cd4203f27aed..4af50e20933b 100644
>> --- a/rust/kernel/alloc/allocator.rs
>> +++ b/rust/kernel/alloc/allocator.rs
>> @@ -11,12 +11,12 @@
>>  use super::{
>>      AllocError,
>>      Allocator,
>> -    Flags,
>> -    NumaNode, //
>> +    Flags, //
>>  };
>>  
>>  use crate::{
>>      bindings,
>> +    numa::NumaNode,
>>      page, //
>>  };
>>  
>> @@ -122,7 +122,7 @@ unsafe fn call(
>>          // - Those functions provide the guarantees of this function.
>>          let raw_ptr = unsafe {
>>              // If `size == 0` and `ptr != NULL` the memory behind the pointer is freed.
>> -            self.0(ptr.cast(), size, layout.align(), flags.0, nid.0).cast()
>> +            self.0(ptr.cast(), size, layout.align(), flags.0, nid.as_raw()).cast()
>>          };
>>  
>>          let ptr = if size == 0 {
>> diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
>> index c63d6acdbb6f..0fa736c81287 100644
>> --- a/rust/kernel/alloc/kbox.rs
>> +++ b/rust/kernel/alloc/kbox.rs
>> @@ -13,12 +13,12 @@
>>  use super::{
>>      AllocError,
>>      Allocator,
>> -    Flags,
>> -    NumaNode, //
>> +    Flags, //
>>  };
>>  
>>  use crate::{
>>      fmt,
>> +    numa::NumaNode,
>>      page::AsPageIter,
>>      prelude::*,
>>      types::ForeignOwnable, //
>> diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
>> index c7546b9da4fa..b669ca10b3f7 100644
>> --- a/rust/kernel/alloc/kvec.rs
>> +++ b/rust/kernel/alloc/kvec.rs
>> @@ -14,12 +14,12 @@
>>      AllocError,
>>      Allocator,
>>      Box,
>> -    Flags,
>> -    NumaNode, //
>> +    Flags, //
>>  };
>>  
>>  use crate::{
>>      fmt,
>> +    numa::NumaNode,
>>      page::{
>>          AsPageIter,
>>          PAGE_SIZE, //
>> diff --git a/rust/kernel/numa.rs b/rust/kernel/numa.rs
>> index 164e622d325f..4a3a880308f3 100644
>> --- a/rust/kernel/numa.rs
>> +++ b/rust/kernel/numa.rs
>> @@ -4,12 +4,15 @@
>>  //!
>>  //! C header: [`include/linux/nodemask.h`](srctree/include/linux/nodemask.h)
>>  
>> -use crate::bindings;
>>  #[cfg(CONFIG_NUMA)]
>>  use crate::sync::atomic::{
>>      Atomic,
>>      Relaxed, //
>>  };
>> +use crate::{
>> +    bindings,
>> +    prelude::*, //
>> +};
>>  
>>  /// Returns the number of online NUMA nodes.
>>  #[inline]
>> @@ -27,3 +30,33 @@ pub fn num_online_nodes() -> u32 {
>>          bindings::nr_online_nodes
>>      }
>>  }
>> +
>> +/// Non Uniform Memory Access (NUMA) node identifier.
>> +#[derive(Clone, Copy, PartialEq)]
>> +pub struct NumaNode(i32);
>
> FWIW the C type is nodemask_t and this should have mask in the name too. It is
> not an identifier. That said, this is an existing issue, so shouldn't block the
> move.

What makes you say this? This is not a mask, it is a numa node id, which
is represented as i32. `NUMA_NO_NODE` is a valid id.

I am using this to specify domain for block mq queues. If you take a
look at the allocation path:

  blk_mq_alloc_queue
  blk_alloc_queue
  slab_alloc_node

It's an id, named `numa_node`, `node_id`, `node`. Not a mask. Unless I
missed something?

Best regards,
Andreas Hindborg