linux-kernel - [PATCH v4 02/28] rust: alloc: separate `aligned_size` from `krealloc

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Message-ID: <20240805152004.5039-3-dakr@kernel.org>
Date: Mon,  5 Aug 2024 17:19:21 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: ojeda@...nel.org,
	alex.gaynor@...il.com,
	wedsonaf@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	benno.lossin@...ton.me,
	a.hindborg@...sung.com,
	aliceryhl@...gle.com,
	akpm@...ux-foundation.org
Cc: daniel.almeida@...labora.com,
	faith.ekstrand@...labora.com,
	boris.brezillon@...labora.com,
	lina@...hilina.net,
	mcanal@...lia.com,
	zhiw@...dia.com,
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	cjia@...dia.com,
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	linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org,
	linux-mm@...ck.org,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH v4 02/28] rust: alloc: separate `aligned_size` from `krealloc_aligned`

Separate `aligned_size` from `krealloc_aligned`.

Subsequent patches implement `Allocator` derivates, such as `Kmalloc`,
that require `aligned_size` and replace the original `krealloc_aligned`.

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 rust/kernel/alloc/allocator.rs | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index e6ea601f38c6..e7b7eba84acb 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -8,27 +8,36 @@
 
 struct KernelAllocator;
 
-/// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment.
-///
-/// # Safety
-///
-/// - `ptr` can be either null or a pointer which has been allocated by this allocator.
-/// - `new_layout` must have a non-zero size.
-pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 {
+/// Returns a proper size to alloc a new object aligned to `new_layout`'s alignment.
+fn aligned_size(new_layout: Layout) -> usize {
     // Customized layouts from `Layout::from_size_align()` can have size < align, so pad first.
     let layout = new_layout.pad_to_align();
 
     // Note that `layout.size()` (after padding) is guaranteed to be a multiple of `layout.align()`
     // which together with the slab guarantees means the `krealloc` will return a properly aligned
     // object (see comments in `kmalloc()` for more information).
-    let size = layout.size();
+    layout.size()
+}
 
+/// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment.
+///
+/// # Safety
+///
+/// - `ptr` can be either null or a pointer which has been allocated by this allocator.
+/// - `new_layout` must have a non-zero size.
+pub(crate) unsafe fn krealloc_aligned(ptr: *mut u8, new_layout: Layout, flags: Flags) -> *mut u8 {
     // SAFETY:
     // - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the
     //   function safety requirement.
     // - `size` is greater than 0 since it's from `layout.size()` (which cannot be zero according
     //   to the function safety requirement)
-    unsafe { bindings::krealloc(ptr as *const core::ffi::c_void, size, flags.0) as *mut u8 }
+    unsafe {
+        bindings::krealloc(
+            ptr as *const core::ffi::c_void,
+            aligned_size(new_layout),
+            flags.0,
+        ) as *mut u8
+    }
 }
 
 unsafe impl GlobalAlloc for KernelAllocator {
-- 
2.45.2