Add a new trait `Ownable` and type `Owned` for types that specify their own way of performing allocation and destruction. This is useful for types from the C side.
Implement `ForeignOwnable` for `Owned`. Convert `Page` to `AlwaysRefCounted` and add a `from_raw()` method. `struct page` is managed by a native reference count, so pages are modelled as shared, reference counted objects rather than exclusively owned ones. Add `ExclusivePage`, an `Ownable` wrapper around `Page` with the added invariant that the page data is free from data races. Add the trait `OwnableRefCounted` that allows conversion between `ARef` and `Owned`. This is analogous to conversion between `Arc` and `UniqueArc`. Patches 1-3 implement `Ownable` and can be merged on their own. Patches 4-5 split the `RefCounted` trait out of `AlwaysRefCounted` and complete the SAFETY documentation for the `ARef` example. Patch 6 adds `Ownable` -> `ARef` interop via `OwnableRefCounted` and can be merged later if consensus on its shape cannot be reached. Patches 7-9 convert `Page` to `AlwaysRefCounted`, add `Page::from_raw()`, and add `ExclusivePage` as the first in-tree `Ownable` user. Signed-off-by: Andreas Hindborg <[email protected]> --- Changes in v21: - Require callers of `Owned::from_raw()` to treat the pointee as pinned (Sashiko). - Import `Page` directly in `allocator.rs` instead of using the `page::Page` path (Danilo). - Update DRM GPUVM for the `RefCounted`/`AlwaysRefCounted` split (Sashiko). - Rework the SAFETY comments in the `ARef::into_raw` doctest to justify the correct obligations (Sashiko). - Use `sync::Refcount` in the `OwnableRefCounted` example (Gary, Danilo). - Add a link to the SAFETY TODO tracking issue to the `ARef` example patch (Miguel). - Convert `Page` to `AlwaysRefCounted` backed by `get_page()` and `put_page()` instead of `Ownable`, and return `ARef<Page>` from `Page::alloc_page()` (Alice). - Update Rust Binder to store `ARef<Page>` instead of `Owned<Page>` (Alice). - Add `ExclusivePage` as the in-tree `Owned` user, without `Deref<Target = Page>` as that would break its aliasing invariant. The type was previously posted as `SafePage` and is renamed here (Alice). - Reorder the series to keep the `Page` patches together at the end. - Link to v20: https://msgid.link/[email protected] Changes in v20: - Fix a few copy/paste errors in safety comments (Sashiko). - Use `self.page.get()` rather than `Opaque::cast_into` (Alice). - Add a space between generics in a comment (Sashiko). - Change a safety comment to reference Box rather than KBox (Sashiko). - Link to v19: https://msgid.link/[email protected] Changes in v19: - Update `workqueue.rs` and the `aref` module docs to use `RefCounted` instead of `AlwaysRefCounted` (Sashiko). - Remove the default `OwnableRefCounted::into_shared` implementation to keep the trait safe (Sashiko). - Fix the `ARef<Self>` rustdoc link (Sashiko). - Reuse `Owned::into_raw`/`from_raw` in the `ForeignOwnable` implementation (Gary). - Link to v18: https://msgid.link/[email protected] Changes in v18: - Rebase on `rust-next` (2026-06-24). - Drop the `'static` bound on `ForeignOwnable for Owned` (Gary). - Make `Ownable::release` take a raw pointer instead of `&mut self` (Alice, Sashiko). - Drop `types::ARef` re-export (Alice). - Drop unneeded `#[repr(transparent)]` on `Owned` (Gary). - Fix `FOREIGN_ALIGN` for `Owned` to report the pointee alignment (Sashiko). - Remove `BorrowedPage`; use `&Page` directly (Alice). - Update Rust Binder for the `Owned<Page>` conversion (Alice). - Update `pwm.rs` for the `RefCounted`/`AlwaysRefCounted` split (Sashiko). - Fix documentation nits: missing `// INVARIANT:` comments, stale `Page` docs, and a stray `mut` (Sashiko). - Expand the `use` statements touched by the rename patch to the multi-line style (Onur). - Link to v17: https://msgid.link/[email protected] Changes in v17: - Rebase on v7.1-rc2. - Reorder patches so that `Ownable` can merge without `OwnableRefCounted` (Alice). - Add `#[inline]` directives to short functions added by the series (Gary). - Link to v16: https://msgid.link/[email protected] Changes in v16: - Simplify pointer to reference cast in `Page::from_raw`. - Use `NonNull<Page>` rather than `Owned<Page>` for `BorrowedPage` internals. - Use "convertible to reference" wording when converting pointers to references. - Fix formatting for `Page::from_raw` docs. - Leave imports alone when adding safety comment to aref example. - Use `KBox::into_nonnull` for examples. - Add patch for `KBox::into_nonnull`. - Change invariants and safety comments of `Ownable` and make the trait safe. - Make `Ownable::release` take a mutable reference. - Fix error handling in example for `Ownable` - Link to v15: https://msgid.link/[email protected] Changes in v15: - Update series with original SoB's. - Rename `AlwaysRefCounted` in `kernel::usb`. - Rename `Owned::get_pin_mut` to `Owned::as_pin_mut`. - Link to v14: https://msgid.link/[email protected] Changes in v14: - Rebase on v6.19-rc7. - Rewrite cover letter. - Update documentation and safety comments based on v13 feedback. - Update commit messages. - Reorder implementation blocks in owned.rs. - Update example in owned.rs to use try operator rather than `expect`. - Reformat use statements. - Add patch: rust: page: convert to `Ownable`. - Add patch: rust: implement `ForeignOwnable` for `Owned`. - Add patch: rust: page: add `from_raw()`. - Link to v13: https://lore.kernel.org/r/[email protected] Changes in v13: - Rebase onto v6.18-rc1 (Andreas's work). - Documentation and style fixes contributed by Andreas - Link to v12: https://lore.kernel.org/r/[email protected] Changes in v12: - - Rebase onto v6.17-rc1 (Andreas's work). - moved kernel/types/ownable.rs to kernel/owned.rs - Drop OwnableMut, make DerefMut depend on Unpin instead. I understood ML discussion as that being okay, but probably needs further scrunity. - Lots of more documentation changes suggested by reviewers. - Usage example for Ownable/Owned. - Link to v11: https://lore.kernel.org/r/[email protected] Changes in v11: - Rework of documentation. I tried to honor all requests for changes "in spirit" plus some clearifications and corrections of my own. - Dropping `SimpleOwnedRefCounted` by request from Alice, as it creates a potentially problematic blanket implementation (which a derive macro that could be created later would not have). - Dropping Miguel's "kbuild: provide `RUSTC_HAS_DO_NOT_RECOMMEND` symbol" patch, as it is not needed anymore after dropping `SimpleOwnedRefCounted`. (I can add it again, if it is considered useful anyway). - Link to v10: https://lore.kernel.org/r/[email protected] Changes in v10: - Moved kernel/ownable.rs to kernel/types/ownable.rs - Fixes in documentation / comments as suggested by Andreas Hindborg - Added Reviewed-by comment for Andreas Hindborg - Fix rustfmt of pid_namespace.rs - Link to v9: https://lore.kernel.org/r/[email protected] Changes in v9: - Rebase onto v6.14-rc7 - Move Ownable/OwnedRefCounted/Ownable, etc., into separate module - Documentation fixes to Ownable/OwnableMut/OwnableRefCounted - Add missing SAFETY documentation to ARef example - Link to v8: https://lore.kernel.org/r/[email protected] Changes in v8: - Fix Co-developed-by and Suggested-by tags as suggested by Miguel and Boqun - Some small documentation fixes in Owned/Ownable patch - removing redundant trait constraint on DerefMut for Owned as suggested by Boqun Feng - make SimpleOwnedRefCounted no longer implement RefCounted as suggested by Boqun Feng - documentation for RefCounted as suggested by Boqun Feng - Link to v7: https://lore.kernel.org/r/[email protected] Changes in v7: - Squash patch to make Owned::from_raw/into_raw public into parent - Added Signed-off-by to other people's commits - Link to v6: https://lore.kernel.org/r/[email protected] Changes in v6: - Changed comments/formatting as suggested by Miguel Ojeda - Included and used new config flag RUSTC_HAS_DO_NOT_RECOMMEND, thus no changes to types.rs will be needed when the attribute becomes available. - Fixed commit message for Owned patch. - Link to v5: https://lore.kernel.org/r/[email protected] Changes in v5: - Rebase the whole thing on top of the Ownable/Owned traits by Asahi Lina. - Rename AlwaysRefCounted to RefCounted and make AlwaysRefCounted a marker trait instead to allow to obtain an ARef<T> from an &T, which (as Alice pointed out) is unsound when combined with UniqueRef/Owned. - Change the Trait design and naming to implement this feature, UniqueRef/UniqueRefCounted is dropped in favor of Ownable/Owned and OwnableRefCounted is used to provide the functions to convert between Owned and ARef. - Link to v4: https://lore.kernel.org/r/[email protected] Changes in v4: - Just a minor change in naming by request from Andreas Hindborg, try_shared_to_unique() -> try_from_shared(), unique_to_shared() -> into_shared(), which is more in line with standard Rust naming conventions. - Link to v3: https://lore.kernel.org/r/Z8Wuud2UQX6Yukyr@mango To: Danilo Krummrich <[email protected]> To: Lorenzo Stoakes <[email protected]> To: Vlastimil Babka <[email protected]> To: "Liam R. Howlett" <[email protected]> To: Uladzislau Rezki <[email protected]> To: Miguel Ojeda <[email protected]> To: Boqun Feng <[email protected]> To: Gary Guo <[email protected]> To: Björn Roy Baron <[email protected]> To: Benno Lossin <[email protected]> To: Andreas Hindborg <[email protected]> To: Alice Ryhl <[email protected]> To: Trevor Gross <[email protected]> To: Daniel Almeida <[email protected]> To: Tamir Duberstein <[email protected]> To: Alexandre Courbot <[email protected]> To: Onur Özkan <[email protected]> To: Lyude Paul <[email protected]> To: Greg Kroah-Hartman <[email protected]> To: Arve Hjønnevåg <[email protected]> To: Todd Kjos <[email protected]> To: Christian Brauner <[email protected]> To: Carlos Llamas <[email protected]> To: "Rafael J. Wysocki" <[email protected]> To: Dave Ertman <[email protected]> To: Ira Weiny <[email protected]> To: Leon Romanovsky <[email protected]> To: Paul Moore <[email protected]> To: Serge Hallyn <[email protected]> To: David Airlie <[email protected]> To: Simona Vetter <[email protected]> To: Alexander Viro <[email protected]> To: Jan Kara <[email protected]> To: Igor Korotin <[email protected]> To: Viresh Kumar <[email protected]> To: Nishanth Menon <[email protected]> To: Stephen Boyd <[email protected]> To: Bjorn Helgaas <[email protected]> To: Krzysztof Wilczyński <[email protected]> To: Pavel Tikhomirov <[email protected]> To: Michal Wilczynski <[email protected]> To: Ira Weiny <[email protected]> To: Matthew Brost <[email protected]> To: Thomas Hellström <[email protected]> Cc: Philipp Stanner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] --- Andreas Hindborg (5): rust: alloc: add `KBox::into_non_null` rust: implement `ForeignOwnable` for `Owned` rust: page: convert to `AlwaysRefCounted` rust: page: add `from_raw()` rust: page: add `ExclusivePage` for race-free page access Asahi Lina (1): rust: types: Add Ownable/Owned types Oliver Mangold (3): rust: rename `AlwaysRefCounted` to `RefCounted`. rust: Add missing SAFETY documentation for `ARef` example rust: Add `OwnableRefCounted` drivers/android/binder/page_range.rs | 8 +- rust/helpers/page.c | 10 + rust/kernel/alloc/allocator.rs | 21 +- rust/kernel/alloc/allocator/iter.rs | 6 +- rust/kernel/alloc/kbox.rs | 9 + rust/kernel/auxiliary.rs | 10 +- rust/kernel/block/mq/request.rs | 19 +- rust/kernel/cred.rs | 16 +- rust/kernel/device.rs | 12 +- rust/kernel/device/property.rs | 11 +- rust/kernel/drm/device.rs | 9 +- rust/kernel/drm/gem/mod.rs | 16 +- rust/kernel/drm/gpuvm/mod.rs | 9 +- rust/kernel/drm/gpuvm/vm_bo.rs | 6 +- rust/kernel/fs/file.rs | 23 ++- rust/kernel/i2c.rs | 13 +- rust/kernel/lib.rs | 1 + rust/kernel/mm.rs | 22 +- rust/kernel/mm/mmput_async.rs | 12 +- rust/kernel/opp.rs | 16 +- rust/kernel/owned.rs | 378 +++++++++++++++++++++++++++++++++++ rust/kernel/page.rs | 206 ++++++++++--------- rust/kernel/pci.rs | 10 +- rust/kernel/pid_namespace.rs | 15 +- rust/kernel/platform.rs | 10 +- rust/kernel/pwm.rs | 12 +- rust/kernel/sync/aref.rs | 87 +++++--- rust/kernel/task.rs | 13 +- rust/kernel/types.rs | 12 ++ rust/kernel/usb.rs | 17 +- rust/kernel/workqueue.rs | 8 +- 31 files changed, 828 insertions(+), 189 deletions(-) --- base-commit: df2908090cda368b01ff43709f51890076c56157 change-id: 20250305-unique-ref-29fcd675f9e9 Best regards, -- Andreas Hindborg <[email protected]>
