[PATCH v2 0/5] 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 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 (5):
      maple_tree: remove lockdep_map_p typedef
      rust: maple_tree: add MapleTree
      rust: maple_tree: add MapleTree::lock() and load()
      rust: maple_tree: add MapleTreeAlloc
      rust: maple_tree: add MAINTAINERS entry

 MAINTAINERS                |  12 +
 include/linux/maple_tree.h |  11 +-
 rust/helpers/helpers.c     |   1 +
 rust/helpers/maple_tree.c  |   8 +
 rust/kernel/lib.rs         |   1 +
 rust/kernel/maple_tree.rs  | 640 +++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 669 insertions(+), 4 deletions(-)
---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250726-maple-tree-1af0803ac524

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