[PATCH v6 0/5] New trait OwnableRefCounted for ARef<->Owned conversion.

[Oliver Mangold]

This allows to convert between ARef<T> and Owned<T> by
implementing the new trait OwnedRefCounted.

This way we will have a shared/unique reference counting scheme
for types with built-in refcounts in analogy to Arc/UniqueArc.

Signed-off-by: Oliver Mangold <oliver.mangold@xxxxx>
---
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/20250307-unique-ref-v5-0-bffeb633277e@xxxxx

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/20250305-unique-ref-v4-1-a8fdef7b1c2c@xxxxx

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

---
Asahi Lina (1):
      rust: types: Add Ownable/Owned types

Miguel Ojeda (1):
      rust: kbuild: provide `RUSTC_HAS_DO_NOT_RECOMMEND` symbol

Oliver Mangold (3):
      rust: make Owned::into_raw() and Owned::from_raw() public
      rust: rename AlwaysRefCounted to RefCounted
      rust: adding OwnableRefCounted and SimpleOwnableRefCounted

 init/Kconfig                    |   3 +
 rust/kernel/block/mq/request.rs |  10 +-
 rust/kernel/cred.rs             |   8 +-
 rust/kernel/device.rs           |   8 +-
 rust/kernel/fs/file.rs          |  10 +-
 rust/kernel/pid_namespace.rs    |   8 +-
 rust/kernel/task.rs             |   6 +-
 rust/kernel/types.rs            | 429 ++++++++++++++++++++++++++++++++++++++--
 8 files changed, 451 insertions(+), 31 deletions(-)
---
base-commit: 4b2ee22fe32ea9b255926effbb6f26450607c391
change-id: 20250305-unique-ref-29fcd675f9e9

Best regards,
-- 
Oliver Mangold <oliver.mangold@xxxxx>