[PATCH v4 00/11] rust: xarray: add entry API with preloading

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

This patch series is a mashup of cleanups, bugfixes and feature additions for
the Rust XArray abstractions.

 - Patch 1 starts by fixing minor formatting issues and bringing use
   statements up to date with the new coding guidelines.

 - Patch 2 add some minor convenience functionality.

 - Patch 3 adds an abstraction for the C `xa_state` structure. This is a
   prerequisite for all the subsequent patches.

 - Patch 4 removes an unnecessary rcu lock in `xarray::Guard::load`.

 - Patch 5 is a simplifying refactor of `xarray::Guard::load`.

 - Patch 6 adds two new methods for finding items with keys that are larger
   than a given integer.

 - Patch 7 adds an entry API.

 - Patch 8-9 adds support for object caches based on sheafs.

 - Patch 10 enables sheafs for the xarray kmem_cache.

 - Patch 11 adds preloading to the new entry API.

The feature additions in this series are dependencies for the rust null
block driver, most of which is still downstream.

Best regards,
Andreas

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
Changes in v4:
- Rebase on v7.1-rc2.
- Drop `contains_index` patch (Tamir).
- Use `kernel::fmt::*` rather than `core::fmt::*` (Tamir).
- Add `into_guard` to `VacantEntry` and `OccupiedEntry` for releasing the entry borrow while keeping the lock guard (Alice).
- Refactor `XArrayState` over a new `GuardRef` trait to support both `&Guard` and `&mut Guard` borrows.
- Improve the `XArrayState` type invariant and update SAFETY comments.
- Document the `(size_t)XAS_RESTART` cast in `bindings_helper.h` (Tamir).
- Use GFP_ATOMIC when allocating under spinlock in the examples.
- Link to v3: https://msgid.link/20260209-xarray-entry-send-v3-0-f777c65b8ae2@kernel.org

Changes in v3:
- Fix a misconception about sheaf availablility under `CONFIG_SLUB_TINY` and `CONFIG_SLUB_DEBUG`.
- Add missing patch to enable sheaf support in xarray kmem_cache.
- Update commit messages for last 3 patches.
- Link to v2: https://msgid.link/20260206-xarray-entry-send-v2-0-91c41673fd30@kernel.org

Changes in v2:
- Rebase on v6.19-rc8.
- Update the cover letter.
- Implement preloading with sheafs.
- Investigate generating RUST_CONST_HELPER_XAS_RESTART as pointer -> Not possible.
- Correct wording of commit message for patch "rust: xarray: use `xas_load` instead of `xa_load` in `Guard::load`".
- Correct wording of commit message for patch "rust: xarray: add `find_next` and `find_next_mut`".
- Remove last patch (lockdep static key fix) from series, to be sent separately.
- Expand note on why store to occupied slot cannot fail.
- Change signature of `OccupiedEntry::swap` to match core::mem::swap.
- Move // NOTEs about storing NULL closer to relevant checks.
- Move `insert_internal` to `XArrayState`.
- Share logic between `find_next` and `find_next_entry`.
- Rename `XArray::get_entry` to `XArray::entry`.
- Make `load_next` a method on `XArrayState`.
- Move load logic to `XArrayState`.
- Use `PhantomData` to capture lifetime of `Guard` for `XArrayState`.
- Link to v1: https://lore.kernel.org/r/20251203-xarray-entry-send-v1-0-9e5ffd5e3cf0@kernel.org

---
Andreas Hindborg (11):
      rust: xarray: minor formatting fixes
      rust: xarray: add debug format for `StoreError`
      rust: xarray: add `XArrayState`
      rust: xarray: use `xas_load` instead of `xa_load` in `Guard::load`
      rust: xarray: simplify `Guard::load`
      rust: xarray: add `find_next` and `find_next_mut`
      rust: xarray: add entry API
      rust: mm: add abstractions for allocating from a `sheaf`
      rust: mm: sheaf: allow use of C initialized static caches
      xarray, radix-tree: enable sheaf support for kmem_cache
      rust: xarray: add preload API

 MAINTAINERS                     |   1 +
 include/linux/radix-tree.h      |   3 +
 lib/radix-tree.c                |  19 +-
 mm/slub.c                       |   4 +
 rust/bindings/bindings_helper.h |  10 +
 rust/helpers/xarray.c           |  17 +
 rust/kernel/mm.rs               |   1 +
 rust/kernel/mm/sheaf.rs         | 690 ++++++++++++++++++++++++++++++++++++++++
 rust/kernel/xarray.rs           | 502 +++++++++++++++++++++++++++--
 rust/kernel/xarray/entry.rs     | 396 +++++++++++++++++++++++
 10 files changed, 1605 insertions(+), 38 deletions(-)
---
base-commit: 7fd2df204f342fc17d1a0bfcd474b24232fb0f32
change-id: 20251203-xarray-entry-send-00230f0744e6

Best regards,
-- 
Andreas Hindborg <a.hindborg@kernel.org>