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Message-Id: <20250627181650.2081123-1-vitaly.wool@konsulko.se>
Date: Fri, 27 Jun 2025 20:16:50 +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 v6 4/4] rust: support large alignments in allocations
Add support for large (> PAGE_SIZE) alignments in Rust allocators.
All the preparations on the C side are already done, we just need
to add bindings for <alloc>_node_align() functions and start
using those.
Signed-off-by: Vitaly Wool <vitaly.wool@...sulko.se>
---
rust/helpers/slab.c | 14 ++++++++++++++
rust/helpers/vmalloc.c | 7 +++++++
rust/kernel/alloc/allocator.rs | 34 +++++++++++-----------------------
3 files changed, 32 insertions(+), 23 deletions(-)
diff --git a/rust/helpers/slab.c b/rust/helpers/slab.c
index 5abd552ccbd4..c4bb451bcf4e 100644
--- a/rust/helpers/slab.c
+++ b/rust/helpers/slab.c
@@ -25,3 +25,17 @@ rust_helper_kvrealloc_node(const void *p, size_t size, gfp_t flags, int node)
{
return kvrealloc_node(p, size, flags, node);
}
+
+void * __must_check __realloc_size(2)
+rust_helper_krealloc_node_align(const void *objp, size_t new_size, unsigned long align,
+ gfp_t flags, int node)
+{
+ return krealloc_node_align(objp, new_size, align, flags, node);
+}
+
+void * __must_check __realloc_size(2)
+rust_helper_kvrealloc_node_align(const void *p, size_t size, unsigned long align,
+ gfp_t flags, int node)
+{
+ return kvrealloc_node_align(p, size, align, flags, node);
+}
diff --git a/rust/helpers/vmalloc.c b/rust/helpers/vmalloc.c
index e6c796c65ee1..09aee472340f 100644
--- a/rust/helpers/vmalloc.c
+++ b/rust/helpers/vmalloc.c
@@ -13,3 +13,10 @@ rust_helper_vrealloc_node(const void *p, size_t size, gfp_t flags, int node)
{
return vrealloc_node(p, size, flags, node);
}
+
+void * __must_check __realloc_size(2)
+rust_helper_vrealloc_node_align(const void *p, size_t size, unsigned long align,
+ gfp_t flags, int node)
+{
+ return vrealloc_node_align(p, size, align, flags, node);
+}
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index 47d9668c3599..7f986c974150 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -59,19 +59,19 @@ fn aligned_size(new_layout: Layout) -> usize {
/// One of the following: `krealloc`, `vrealloc`, `kvrealloc`.
struct ReallocFunc(
unsafe extern "C" fn(
- *const crate::ffi::c_void, usize, u32, crate::ffi::c_int
+ *const crate::ffi::c_void, usize, crate::ffi::c_ulong, u32, crate::ffi::c_int,
) -> *mut crate::ffi::c_void,
);
impl ReallocFunc {
- // INVARIANT: `krealloc_node` satisfies the type invariants.
- const KREALLOC_NODE: Self = Self(bindings::krealloc_node);
+ // INVARIANT: `krealloc_node_align` satisfies the type invariants.
+ const KREALLOC_NODE_ALIGN: Self = Self(bindings::krealloc_node_align);
- // INVARIANT: `vrealloc_node` satisfies the type invariants.
- const VREALLOC_NODE: Self = Self(bindings::vrealloc_node);
+ // INVARIANT: `vrealloc_node_align` satisfies the type invariants.
+ const VREALLOC_NODE_ALIGN: Self = Self(bindings::vrealloc_node_align);
- // INVARIANT: `kvrealloc_node` satisfies the type invariants.
- const KVREALLOC_NODE: Self = Self(bindings::kvrealloc_node);
+ // INVARIANT: `kvrealloc_node_align` satisfies the type invariants.
+ const KVREALLOC_NODE_ALIGN: Self = Self(bindings::kvrealloc_node_align);
/// # Safety
///
@@ -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, flags.0, c_nid).cast()
+ self.0(ptr.cast(), size, layout.align(), flags.0, c_nid).cast()
};
let ptr = if size == 0 {
@@ -145,7 +145,7 @@ unsafe fn realloc(
nid: Option<i32>,
) -> Result<NonNull<[u8]>, AllocError> {
// SAFETY: `ReallocFunc::call` has the same safety requirements as `Allocator::realloc`.
- unsafe { ReallocFunc::KREALLOC_NODE.call(ptr, layout, old_layout, flags, nid) }
+ unsafe { ReallocFunc::KREALLOC_NODE_ALIGN.call(ptr, layout, old_layout, flags, nid) }
}
}
@@ -162,15 +162,9 @@ 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) }
+ unsafe { ReallocFunc::VREALLOC_NODE_ALIGN.call(ptr, layout, old_layout, flags, nid) }
}
}
@@ -187,14 +181,8 @@ 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) }
+ unsafe { ReallocFunc::KVREALLOC_NODE_ALIGN.call(ptr, layout, old_layout, flags, nid) }
}
}
--
2.39.2
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