[PATCH v3 0/3] Add Rust abstraction for Maple Trees

[Alice Ryhl <aliceryhl@google.com>]

This will be used in the Tyr driver [1] to allocate from the GPU's VA
space that is not owned by userspace, but by the kernel, for kernel GPU
mappings.

Danilo tells me that in nouveau, the maple tree is used for keeping
track of "VM regions" on top of GPUVM, and that he will most likely end
up doing the same in the Rust Nova driver as well.

These abstractions intentionally do not expose any way to make use of
external locking. You are required to use the internal spinlock. For
now, we do not support loads that only utilize rcu for protection.

This contains some parts taken from Andrew Ballance's RFC [2] from
April. However, it has also been reworked significantly compared to that
RFC taking the use-cases in Tyr into account.

[1]: https://lore.kernel.org/r/20250627-tyr-v1-1-cb5f4c6ced46@collabora.com
[2]: https://lore.kernel.org/r/20250405060154.1550858-1-andrewjballance@gmail.com

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
Changes in v3:
- Change examples to avoid unwrap(), but not unwrap_err().
- Remove spurious MAINTAINERS change.
- Fix unnnecessary imports.
- Drop lockdep_map_p patch from this series.
- Reword MaState type invariant.
- Various docs improvements.
- Rename mas_find() to find().
- Add to existing MAINTAINERS entry.
- Link to v2: https://lore.kernel.org/r/20250819-maple-tree-v2-0-229b48657bab@google.com

Changes in v2:
- Add MaState abstraction. For now it only has a mas_find method. And
  use it in the destructor.
- Duplicate MA_STATE macro in Rust instead of using a C helper.
- Change maple_tree.h so that cast in ma_lock() is no longer needed.
- Add #[must_use] and #[inline] annotations.
- Rename MapleLock to MapleGuard.
- Change errors to use AllocError.
- Add MAINTAINERS file.
- Link to v1: https://lore.kernel.org/r/20250726-maple-tree-v1-0-27a3da7cb8e5@google.com

---
Alice Ryhl (3):
      rust: maple_tree: add MapleTree
      rust: maple_tree: add lock guard for maple tree
      rust: maple_tree: add MapleTreeAlloc

 MAINTAINERS                |   4 +
 include/linux/maple_tree.h |   3 +
 rust/helpers/helpers.c     |   1 +
 rust/helpers/maple_tree.c  |   8 +
 rust/kernel/lib.rs         |   1 +
 rust/kernel/maple_tree.rs  | 648 +++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 665 insertions(+)
---
base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00
change-id: 20250726-maple-tree-1af0803ac524

Best regards,
-- 
Alice Ryhl <aliceryhl@google.com>