This patchset contains two useful methods for the Arc type. They will be
used in my Rust linked list implementation, which Rust Binder uses. See
the Rust Binder RFC [1] for more information. Both these commits and
the linked list that uses them are present in the branch referenced by
the RFC.

I will send the linked list to the mailing list soon.

Link: https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-0-08ba9197f637@google.com/ [1]
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
Changes in v3:
- No changes to `ArcBorrow::from_raw`, or than adding a Reviewed-by.
- Update SAFETY comment on `refcount_dec_and_test` call.
- Simplify the creation of the `UniqueArc` in `into_unique_or_drop`.
- Link to v2: https://lore.kernel.org/r/20240228-arc-for-list-v2-0-ae93201426b4@google.com

Changes in v2:
- Move raw_to_inner_ptr to ArcInner and rename to container_of.
- Reword safety conditions for raw_to_inner_ptr to match its users.
- Link to v1: https://lore.kernel.org/r/20240219-arc-for-list-v1-0-d98cd92c760b@google.com

---
Alice Ryhl (2):
      rust: sync: add `ArcBorrow::from_raw`
      rust: sync: add `Arc::into_unique_or_drop`

 rust/kernel/sync/arc.rs | 106 ++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 88 insertions(+), 18 deletions(-)
---
base-commit: 768409cff6cc89fe1194da880537a09857b6e4db
change-id: 20240209-arc-for-list-a2c126c2ad5c

Best regards,
-- 
Alice Ryhl <aliceryhl@google.com>

On Mon, Mar 11, 2024 at 04:08:17PM +0000, Alice Ryhl wrote:
> This patchset contains two useful methods for the Arc type. They will be
> used in my Rust linked list implementation, which Rust Binder uses. See
> the Rust Binder RFC [1] for more information. Both these commits and
> the linked list that uses them are present in the branch referenced by
> the RFC.
> 
> I will send the linked list to the mailing list soon.
> 

For the whole series:

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>

Note there's a nit for rustfmt fix of patch #2 (which is reported by
Miguel):

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 7cf066cfb321..c9773d0050c2 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -345,7 +345,9 @@ pub fn into_unique_or_drop(self) -> Option<Pin<UniqueArc<T>>> {
             // INVARIANT: We own the only refcount to this arc, so we may create a `UniqueArc`. We
             // must pin the `UniqueArc` because the values was previously in an `Arc`, and they pin
             // their values.
-            Some(Pin::from(UniqueArc { inner: ManuallyDrop::into_inner(me) }))
+            Some(Pin::from(UniqueArc {
+                inner: ManuallyDrop::into_inner(me),
+            }))
         } else {
             None
         }

Regards,
Boqun

> Link: https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-0-08ba9197f637@google.com/ [1]
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---
> Changes in v3:
> - No changes to `ArcBorrow::from_raw`, or than adding a Reviewed-by.
> - Update SAFETY comment on `refcount_dec_and_test` call.
> - Simplify the creation of the `UniqueArc` in `into_unique_or_drop`.
> - Link to v2: https://lore.kernel.org/r/20240228-arc-for-list-v2-0-ae93201426b4@google.com
> 
> Changes in v2:
> - Move raw_to_inner_ptr to ArcInner and rename to container_of.
> - Reword safety conditions for raw_to_inner_ptr to match its users.
> - Link to v1: https://lore.kernel.org/r/20240219-arc-for-list-v1-0-d98cd92c760b@google.com
> 
> ---
> Alice Ryhl (2):
>       rust: sync: add `ArcBorrow::from_raw`
>       rust: sync: add `Arc::into_unique_or_drop`
> 
>  rust/kernel/sync/arc.rs | 106 ++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 88 insertions(+), 18 deletions(-)
> ---
> base-commit: 768409cff6cc89fe1194da880537a09857b6e4db
> change-id: 20240209-arc-for-list-a2c126c2ad5c
> 
> Best regards,
> -- 
> Alice Ryhl <aliceryhl@google.com>
>