[PATCH v5 4/4] rust: support large alignments in allocations

From: Vitaly Wool
Date: Fri Jun 27 2025 - 05:39:35 EST


Add support for large (> PAGE_SIZE) alignments in Rust allocators.
With _NODE primitives introduced in the previous patch, we actually
have all the infractructure in place so let's just start using it.

Signed-off-by: Vitaly Wool <vitaly.wool@xxxxxxxxxxx>
---
rust/kernel/alloc/allocator.rs | 14 +-------------
1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 4f0fe2b67593..75c9e4220ac3 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -118,7 +118,7 @@ unsafe fn call(
// - Those functions provide the guarantees of this function.
let raw_ptr = unsafe {
// If `size == 0` and `ptr != NULL` the memory behind the pointer is freed.
- self.0(ptr.cast(), size, 1, flags.0, c_nid).cast()
+ self.0(ptr.cast(), size, layout.align(), flags.0, c_nid).cast()
};

let ptr = if size == 0 {
@@ -162,12 +162,6 @@ unsafe fn realloc(
flags: Flags,
nid: Option<i32>,
) -> Result<NonNull<[u8]>, AllocError> {
- // TODO: Support alignments larger than PAGE_SIZE.
- if layout.align() > bindings::PAGE_SIZE {
- pr_warn!("Vmalloc does not support alignments larger than PAGE_SIZE yet.\n");
- return Err(AllocError);
- }
-
// SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
// allocated with this `Allocator`.
unsafe { ReallocFunc::VREALLOC_NODE.call(ptr, layout, old_layout, flags, nid) }
@@ -187,12 +181,6 @@ unsafe fn realloc(
flags: Flags,
nid: Option<i32>,
) -> Result<NonNull<[u8]>, AllocError> {
- // 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");
- return Err(AllocError);
- }
-
// SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
// allocated with this `Allocator`.
unsafe { ReallocFunc::KVREALLOC_NODE.call(ptr, layout, old_layout, flags, nid) }
--
2.39.2