Add an associated function to convert a `Box<T>` into a `Pin<Box<T>>`.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/alloc/kbox.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
index cb4ebea3b074..9da4a32e60bc 100644
--- a/rust/kernel/alloc/kbox.rs
+++ b/rust/kernel/alloc/kbox.rs
@@ -245,6 +245,12 @@ pub fn pin(x: T, flags: Flags) -> Result<Pin<Box<T, A>>, AllocError>
         Ok(Self::new(x, flags)?.into())
     }
 
+    /// Convert a [`Box<T,A>`] to a [`Pin<Box<T,A>>`]. If `T` does not implement
+    /// [`Unpin`], then `x` will be pinned in memory and can't be moved.
+    pub fn into_pin(this: Self) -> Pin<Self> {
+        this.into()
+    }
+
     /// Forgets the contents (does not run the destructor), but keeps the allocation.
     fn forget_contents(this: Self) -> Box<MaybeUninit<T>, A> {
         let ptr = Self::into_raw(this);

-- 
2.47.0