Re: [PATCH 1/3] rust: revocable: update write invariant and fix safety comments

[Marcelo Moreira <marcelomoreira1905@gmail.com>]

[PATCH v4 0/3]

rust: revocable: documentation and refactorings

This series of patches brings documentation and refactorings to the
`Revocable` type.

The main changes include:
- Clarifying the write invariant and updating associated safety
comments for `Revocable<T>`.
- Refactoring `RevocableGuard` to be internally safe by holding a
direct reference (`&'a T`), simplifying its usage and reducing unsafe
code.
- Splitting the internal `revoke_internal` function into two distinct,
explicit functions: `revoke()` (safe, synchronizing with RCU) and
`revoke_nosync()` (unsafe, without RCU synchronization).

This is v4 of the patch series.

Changes since v3:
- Refined the wording of the `Revocable<T>` invariants to be more
precise about read and write validity conditions, specifically
including RCU read-side lock acquisition timing for reads and RCU
grace period for writes. - Simplified the `try_access_with_guard`
safety comment for better conciseness.
- Refactored `RevocableGuard` to use `&'a T` instead of `*const T`,
removing its internal invariants and `unsafe` blocks.
- Simplified `Revocable::try_access` to leverage
`try_access_with_guard` and `map`.
- Split `revoke_internal` into `revoke()` and `revoke_nosync()`
functions, making synchronization behavior explicit.
- Link to v3: https://lore.kernel.org/rust-for-linux/DA6XFLKUTP1P.RR6P5AK9PKIZ@kernel.org/T/#t

Changes in v2:
- Refined the wording of the invariants in `Revocable<T>` to be more
direct and address feedback regarding the phrase 'must occur'.
- Added '// INVARIANT:' comments in `try_access` and
`try_access_with_guard` as suggested by reviewers.
- Added the missing invariant for `RevocableGuard<'_, T>` regarding
the validity of `data_ref`.
- Updated the safety comment in the `Deref` implementation of
`RevocableGuard` to refer to the new invariant.
- Link to v2: https://lore.kernel.org/rust-for-linux/CAPZ3m_jw0LxK1MmseaamNYhj9VY8AXtJ0AOcYd9qcn=5wPE4eA@mail.gmail.com/T/#t

Signed-off-by: Marcelo Moreira <marcelomoreira1905@gmail.com>

---
Marcelo Moreira (3):

rust: revocable: update write invariant and fix safety comments
rust: revocable: simplify RevocableGuard for internal safety
rust: revocable: split revoke_internal into revoke and revoke_nosync

rust/kernel/revocable.rs | 84
++++++++++++++++++++++++++++++++++++------------------------------------------------
1 file changed, 36 insertions(+), 48 deletions(-)

--- base-commit: 7a17bbc1d952057898cb0739e60665908fbb8c72

Cheers,
Marcelo Moreira