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rust: alloc: separate aligned_size from krealloc_aligned

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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@google.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241004154149.93856-3-dakr@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Danilo Krummrich 2024-10-04 17:41:06 +02:00 committed by Miguel Ojeda
parent b7a084ba4f
commit a654a6e096
1 changed files with 12 additions and 7 deletions
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19
rust/kernel/alloc/allocator.rs
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@ -8,6 +8,17 @@
struct KernelAllocator;
/// 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).
layout.size()
}
/// Calls `krealloc` with a proper size to alloc a new object aligned to `new_layout`'s alignment.
///
/// # Safety
@ -15,13 +26,7 @@
/// - `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 {
// 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();
let size = aligned_size(new_layout);
// SAFETY:
// - `ptr` is either null or a pointer returned from a previous `k{re}alloc()` by the