aligned_size() dates back to when Rust did support kmalloc() only, but
is now used in ReallocFunc::call() and hence for all allocators.
However, the additional padding applied by aligned_size() is only
required by the kmalloc() allocator backend.
Hence, replace aligned_size() with Kmalloc::aligned_layout() and use it
for the affected allocators, i.e. kmalloc() and kvmalloc(), only.
While at it, make Kmalloc::aligned_layout() public, such that Rust
abstractions, which have to call subsystem specific kmalloc() based
allocation primitives directly, can make use of it.
Fixes: 8a799831fc63 ("rust: alloc: implement `ReallocFunc`")
Signed-off-by: Danilo Krummrich <d...@kernel.org>
---
rust/kernel/alloc/allocator.rs | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index aa2dfa9dca4c..3331ef338f3b 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -43,17 +43,6 @@
/// For more details see [self].
pub struct KVmalloc;
-/// 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()
-}
-
/// # Invariants
///
/// One of the following: `krealloc`, `vrealloc`, `kvrealloc`.
@@ -88,7 +77,7 @@ unsafe fn call(
old_layout: Layout,
flags: Flags,
) -> Result<NonNull<[u8]>, AllocError> {
- let size = aligned_size(layout);
+ let size = layout.size();
let ptr = match ptr {
Some(ptr) => {
if old_layout.size() == 0 {
@@ -123,6 +112,17 @@ unsafe fn call(
}
}
+impl Kmalloc {
+ /// Returns a [`Layout`] that makes [`Kmalloc`] fulfill the requested size
and alignment of
+ /// `layout`.
+ pub const fn aligned_layout(layout: Layout) -> Layout {
+ // Note that `layout.size()` (after padding) is guaranteed to be a
multiple of
+ // `layout.align()` which together with the slab guarantees means that
`Kmalloc` will return
+ // a properly aligned object (see comments in `kmalloc()` for more
information).
+ layout.pad_to_align()
+ }
+}
+
// SAFETY: `realloc` delegates to `ReallocFunc::call`, which guarantees that
// - memory remains valid until it is explicitly freed,
// - passing a pointer to a valid memory allocation is OK,
@@ -135,6 +135,8 @@ unsafe fn realloc(
old_layout: Layout,
flags: Flags,
) -> Result<NonNull<[u8]>, AllocError> {
+ let layout = Kmalloc::aligned_layout(layout);
+
// SAFETY: `ReallocFunc::call` has the same safety requirements as
`Allocator::realloc`.
unsafe { ReallocFunc::KREALLOC.call(ptr, layout, old_layout, flags) }
}
@@ -176,6 +178,10 @@ unsafe fn realloc(
old_layout: Layout,
flags: Flags,
) -> Result<NonNull<[u8]>, AllocError> {
+ // `KVmalloc` may use the `Kmalloc` backend, hence we have to enforce
a `Kmalloc`
+ // compatible layout.
+ let layout = Kmalloc::aligned_layout(layout);
+
// TODO: Support alignments larger than PAGE_SIZE.
if layout.align() > bindings::PAGE_SIZE {
pr_warn!("KVmalloc does not support alignments larger than
PAGE_SIZE yet.\n");
--
2.50.0
