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

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Message-Id: <20250627093918.415888-1-vitaly.wool@konsulko.se>
Date: Fri, 27 Jun 2025 11:39:18 +0200
From: Vitaly Wool <vitaly.wool@...sulko.se>
To: linux-mm@...ck.org
Cc: akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	Uladzislau Rezki <urezki@...il.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	rust-for-linux@...r.kernel.org,
	Vitaly Wool <vitaly.wool@...sulko.se>
Subject: [PATCH v5 4/4] rust: support large alignments in allocations

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@...sulko.se>
---
 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