[PATCH v3 0/5] Red-black tree abstraction needed by Rust Binder

[Matt Gilbride]

This patchset contains the red-black tree abstractions needed by the Rust
implementation of the Binder driver.

Binder driver benefits from O(log n) search/insertion/deletion of
key/value mappings in various places, including `process.rs` and
`range_alloc.rs`.  In `range_alloc.rs`, the ability to store and
search by a generic key type is also useful.

Please see the Rust Binder RFC for usage examples [1]. Note that
the `container_of` macro is currently used only by `rbtree` itself.

Users of "rust: rbtree: add red-black tree implementation backed by the C version"
    [PATCH RFC 03/20] rust_binder: add threading support
    [PATCH RFC 05/20] rust_binder: add nodes and context managers
    [PATCH RFC 06/20] rust_binder: add oneway transactions

Users of "rust: rbtree: add `RBTreeIterator`"
    [PATCH RFC 17/20] rust_binder: add oneway spam detection

Users of "rust: rbtree: add `RBTreeIteratorMut`"
    [PATCH RFC 06/20] rust_binder: add oneway transactions

Users of "rust: rbtree: add `RBTreeCursor`"
    [PATCH RFC 06/20] rust_binder: add oneway transactions

Users of "rust: rbtree: add RBTree::entry"
    Not used in the original RFC, but introduced after further
    code review.  See: https://r.android.com/2849906

The Rust Binder RFC addresses the upstream deprecation of red-black
tree. Quoted here for convenience:

"This RFC uses the kernel's red-black tree for key/value mappings, but we
are aware that the red-black tree is deprecated. We did this to make the
performance comparison more fair, since C binder also uses rbtree for
this. We intend to replace these with XArrays instead. That said, we
don't think that XArray is a good fit for the range allocator, and we
propose to continue using the red-black tree for the range allocator."

Link: https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-0-08ba9197f637@xxxxxxxxxx/ [1]
Signed-off-by: Matt Gilbride <mattgilbride@xxxxxxxxxx>
---
Changes in v3:
- Address various feedback re: SAFETY and INVARIANT comments from v2.
- Update variable naming and add detailed comments for the `RBTree::insert` (later moved to
  `RBTree::raw_entry`) implementation.
- Link to v2: https://lore.kernel.org/r/20240219-b4-rbtree-v2-0-0b113aab330d@xxxxxxxxxx

Changes in v2:
- Update documentation link to the C header file
- Use `core::convert::Infallible` in try_reserve_node
- Link to v1: https://lore.kernel.org/r/20240205-b4-rbtree-v1-0-995e3eee38c0@xxxxxxxxxx

---
Alice Ryhl (1):
      rust: rbtree: add `RBTree::entry`

Matt Gilbride (1):
      rust: rbtree: add `RBTreeCursor`

Wedson Almeida Filho (3):
      rust: rbtree: add red-black tree implementation backed by the C version
      rust: rbtree: add `RBTreeIterator`
      rust: rbtree: add `RBTreeIteratorMut`

 rust/helpers.c        |    7 +
 rust/kernel/lib.rs    |    1 +
 rust/kernel/rbtree.rs | 1275 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1283 insertions(+)
---
base-commit: 768409cff6cc89fe1194da880537a09857b6e4db
change-id: 20231205-b4-rbtree-abb1a016f0a0

Best regards,
-- 
Matt Gilbride <mattgilbride@xxxxxxxxxx>