[PATCH 10/10] rust: kernel: remove usage of `allocator_api` unstable feature

[Wedson Almeida Filho <wedsonaf@gmail.com>]

From: Wedson Almeida Filho <walmeida@microsoft.com>

With the adoption of `BoxExt` and `VecExt`, we don't need the functions
provided by this feature (namely the methods prefixed with `try_` and
different allocator per collection instance).

We do need `AllocError`, but we define our own as it is a trivial empty
struct.

Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
---
 rust/kernel/alloc.rs        |  3 +++
 rust/kernel/alloc/boxext.rs |  3 +--
 rust/kernel/alloc/vecext.rs |  4 ++--
 rust/kernel/error.rs        | 13 ++-----------
 rust/kernel/init.rs         |  3 +--
 rust/kernel/lib.rs          |  1 -
 rust/kernel/str.rs          |  3 +--
 rust/kernel/sync/arc.rs     |  4 ++--
 rust/kernel/workqueue.rs    |  3 +--
 9 files changed, 13 insertions(+), 24 deletions(-)

diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index 5712c81b1308..f17f48130f13 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -8,6 +8,9 @@
 pub mod boxext;
 pub mod vecext;
 
+/// Indicates an allocation error.
+pub struct AllocError;
+
 /// Flags to be used when allocating memory.
 ///
 /// They can be combined with the operators `|`, `&`, and `!`.
diff --git a/rust/kernel/alloc/boxext.rs b/rust/kernel/alloc/boxext.rs
index 26a918df7acf..3cdda0f635a3 100644
--- a/rust/kernel/alloc/boxext.rs
+++ b/rust/kernel/alloc/boxext.rs
@@ -2,9 +2,8 @@
 
 //! Extensions to [`Box`] for fallible allocations.
 
-use super::Flags;
+use super::{AllocError, Flags};
 use alloc::boxed::Box;
-use core::alloc::AllocError;
 use core::mem::MaybeUninit;
 use core::result::Result;
 
diff --git a/rust/kernel/alloc/vecext.rs b/rust/kernel/alloc/vecext.rs
index 1d4d51b45a49..85ca6a6db6de 100644
--- a/rust/kernel/alloc/vecext.rs
+++ b/rust/kernel/alloc/vecext.rs
@@ -2,8 +2,8 @@
 
 //! Extensions to [`Vec`] for fallible allocations.
 
-use super::Flags;
-use alloc::{alloc::AllocError, vec::Vec};
+use super::{AllocError, Flags};
+use alloc::vec::Vec;
 use core::{mem::ManuallyDrop, result::Result};
 
 /// Extensions to [`Vec`].
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 4786d3ee1e92..fc986bc24c6d 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -4,12 +4,9 @@
 //!
 //! C header: [`include/uapi/asm-generic/errno-base.h`](srctree/include/uapi/asm-generic/errno-base.h)
 
-use crate::str::CStr;
+use crate::{alloc::AllocError, str::CStr};
 
-use alloc::{
-    alloc::{AllocError, LayoutError},
-    collections::TryReserveError,
-};
+use alloc::alloc::LayoutError;
 
 use core::convert::From;
 use core::fmt;
@@ -192,12 +189,6 @@ fn from(_: Utf8Error) -> Error {
     }
 }
 
-impl From<TryReserveError> for Error {
-    fn from(_: TryReserveError) -> Error {
-        code::ENOMEM
-    }
-}
-
 impl From<LayoutError> for Error {
     fn from(_: LayoutError) -> Error {
         code::ENOMEM
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 1a8b0464db0c..1f7a6b5892ac 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -211,14 +211,13 @@
 //! [`pin_init!`]: crate::pin_init!
 
 use crate::{
-    alloc::{boxext::BoxExt, Flags},
+    alloc::{boxext::BoxExt, AllocError, Flags},
     error::{self, Error},
     sync::UniqueArc,
     types::{Opaque, ScopeGuard},
 };
 use alloc::boxed::Box;
 use core::{
-    alloc::AllocError,
     cell::UnsafeCell,
     convert::Infallible,
     marker::PhantomData,
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 51f30e55bd00..5c641233e26d 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -12,7 +12,6 @@
 //! do so first instead of bypassing this crate.
 
 #![no_std]
-#![feature(allocator_api)]
 #![feature(coerce_unsized)]
 #![feature(dispatch_from_dyn)]
 #![feature(new_uninit)]
diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index 34dbc85b5220..5206b18f882b 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -2,8 +2,7 @@
 
 //! String representations.
 
-use crate::alloc::{flags::*, vecext::VecExt};
-use alloc::alloc::AllocError;
+use crate::alloc::{flags::*, vecext::VecExt, AllocError};
 use alloc::vec::Vec;
 use core::fmt::{self, Write};
 use core::ops::{self, Deref, Index};
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index af539c5eb4bc..8db25f73b37f 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -16,7 +16,7 @@
 //! [`Arc`]: https://doc.rust-lang.org/std/sync/struct.Arc.html
 
 use crate::{
-    alloc::{boxext::BoxExt, Flags},
+    alloc::{boxext::BoxExt, AllocError, Flags},
     bindings,
     error::{self, Error},
     init::{self, InPlaceInit, Init, PinInit},
@@ -25,7 +25,7 @@
 };
 use alloc::boxed::Box;
 use core::{
-    alloc::{AllocError, Layout},
+    alloc::Layout,
     fmt,
     marker::{PhantomData, Unsize},
     mem::{ManuallyDrop, MaybeUninit},
diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 09a0f158ff1b..50837e56efc7 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -132,9 +132,8 @@
 //!
 //! C header: [`include/linux/workqueue.h`](srctree/include/linux/workqueue.h)
 
-use crate::alloc::Flags;
+use crate::alloc::{AllocError, Flags};
 use crate::{bindings, prelude::*, sync::Arc, sync::LockClassKey, types::Opaque};
-use alloc::alloc::AllocError;
 use alloc::boxed::Box;
 use core::marker::PhantomData;
 use core::pin::Pin;
-- 
2.34.1