linux-kernel - Re: [PATCH v3 00/10] Allocation APIs

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Date: Fri, 29 Mar 2024 11:25:00 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Wedson Almeida Filho <wedsonaf@...il.com>
Cc: rust-for-linux@...r.kernel.org, Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...sung.com>,
	Alice Ryhl <aliceryhl@...gle.com>, linux-kernel@...r.kernel.org,
	Wedson Almeida Filho <walmeida@...rosoft.com>
Subject: Re: [PATCH v3 00/10] Allocation APIs

On Wed, Mar 27, 2024 at 10:35:53PM -0300, Wedson Almeida Filho wrote:
> From: Wedson Almeida Filho <walmeida@...rosoft.com>
> 
> Revamp how we use the `alloc` crate.
> 
> We currently have a fork of the crate with changes to `Vec`; other
> changes have been upstreamed (to the Rust project). This series removes
> the fork and exposes all the functionality as extension traits.
> 
> Additionally, it also introduces allocation flag parameters to all
> functions that may result in allocations (e.g., `Box::new`, `Arc::new`,
> `Vec::push`, etc.) without the `try_` prefix -- the names are available
> because we build `alloc` with `no_global_oom_handling`.
> 
> Lastly, the series also removes our reliance on the `allocator_api`
> unstable feature.
> 
> Long term, we still want to make such functionality available in
> upstream Rust, but this allows us to make progress now and reduces our
> maintainance burden.
> 
> In summary:
> 1. Removes `alloc` fork
> 2. Removes use of `allocator_api` unstable feature
> 3. Introduces flags (e.g., GFP_KERNEL, GFP_ATOMIC) when allocating
> 
> ---
> 

FWIW, I've put this into rust-dev:

	https://github.com/Rust-for-Linux/linux rust-dev

a few adjustments are needed to work with other commits that have been
queued in rust-dev, so I add an commit on the top for everyone's
reference. (Besides this commit, I also removed all updates to our own
alloc in Miguel's 1.77.0 compiler version bump patch)

Regards,
Boqun

---------------------------------------------------->8
diff --git a/rust/kernel/file.rs b/rust/kernel/file.rs
index 8902f490ccc8..a5930f0f2bc5 100644
--- a/rust/kernel/file.rs
+++ b/rust/kernel/file.rs
@@ -6,13 +6,15 @@
 //! [`include/linux/file.h`](srctree/include/linux/file.h)
 
 use crate::{
+    alloc::AllocError,
     bindings,
     cred::Credential,
     error::{code::*, Error, Result},
+    prelude::*,
     types::{ARef, AlwaysRefCounted, NotThreadSafe, Opaque},
 };
 use alloc::boxed::Box;
-use core::{alloc::AllocError, mem, ptr};
+use core::{mem, ptr};
 
 /// Flags associated with a [`File`].
 pub mod flags {
@@ -348,10 +350,13 @@ impl DeferredFdCloser {
     pub fn new() -> Result<Self, AllocError> {
         Ok(Self {
             // INVARIANT: The `file` pointer is null, so the type invariant does not apply.
-            inner: Box::try_new(DeferredFdCloserInner {
-                twork: mem::MaybeUninit::uninit(),
-                file: core::ptr::null_mut(),
-            })?,
+            inner: Box::new(
+                DeferredFdCloserInner {
+                    twork: mem::MaybeUninit::uninit(),
+                    file: core::ptr::null_mut(),
+                },
+                GFP_KERNEL,
+            )?,
         })
     }
 
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index c4a5e175b574..13a2166c4f41 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -302,7 +302,7 @@ pub fn ptr_eq(this: &Self, other: &Self) -> bool {
     /// ```
     /// use kernel::sync::{Arc, UniqueArc};
     ///
-    /// let arc = Arc::try_new(42)?;
+    /// let arc = Arc::new(42, GFP_KERNEL)?;
     /// let unique_arc = arc.into_unique_or_drop();
     ///
     /// // The above conversion should succeed since refcount of `arc` is 1.
@@ -316,7 +316,7 @@ pub fn ptr_eq(this: &Self, other: &Self) -> bool {
     /// ```
     /// use kernel::sync::{Arc, UniqueArc};
     ///
-    /// let arc = Arc::try_new(42)?;
+    /// let arc = Arc::new(42, GFP_KERNEL)?;
     /// let another = arc.clone();
     ///
     /// let unique_arc = arc.into_unique_or_drop();