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Message-Id: <20250624123922.3258215-1-vitaly.wool@konsulko.se>
Date: Tue, 24 Jun 2025 14:39:22 +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 v2 2/2] rust: support large align and NUMA ids in allocs
Add support for large (> PAGE_SIZE) alignments in Rust allocators
(Kmalloc support for large alignments is limited to the requested
size, which is a reasonable limitation anyway).
Besides, add support for NUMA id to Vmalloc.
Signed-off-by: Vitaly Wool <vitaly.wool@...sulko.se>
---
rust/helpers/slab.c | 8 +++++--
rust/helpers/vmalloc.c | 4 ++--
rust/kernel/alloc.rs | 28 ++++++++++++++++++++++--
rust/kernel/alloc/allocator.rs | 40 +++++++++++++++++++---------------
rust/kernel/alloc/kvec.rs | 3 ++-
5 files changed, 59 insertions(+), 24 deletions(-)
diff --git a/rust/helpers/slab.c b/rust/helpers/slab.c
index a842bfbddcba..221c517f57a1 100644
--- a/rust/helpers/slab.c
+++ b/rust/helpers/slab.c
@@ -3,13 +3,17 @@
#include <linux/slab.h>
void * __must_check __realloc_size(2)
-rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
+rust_helper_krealloc(const void *objp, size_t new_size, unsigned long align, gfp_t flags, int nid)
{
+ if (WARN_ON(new_size & (align - 1)))
+ return NULL;
return krealloc(objp, new_size, flags);
}
void * __must_check __realloc_size(2)
-rust_helper_kvrealloc(const void *p, size_t size, gfp_t flags)
+rust_helper_kvrealloc(const void *p, size_t size, unsigned long align, gfp_t flags, int nid)
{
+ if (WARN_ON(size & (align - 1)))
+ return NULL;
return kvrealloc(p, size, flags);
}
diff --git a/rust/helpers/vmalloc.c b/rust/helpers/vmalloc.c
index 80d34501bbc0..9131279222fa 100644
--- a/rust/helpers/vmalloc.c
+++ b/rust/helpers/vmalloc.c
@@ -3,7 +3,7 @@
#include <linux/vmalloc.h>
void * __must_check __realloc_size(2)
-rust_helper_vrealloc(const void *p, size_t size, gfp_t flags)
+rust_helper_vrealloc_node(const void *p, size_t size, unsigned long align, gfp_t flags, int node)
{
- return vrealloc(p, size, flags);
+ return vrealloc_node(p, size, align, flags, node);
}
diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index 2e377c52fa07..12a723bf6092 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -161,7 +161,30 @@ pub unsafe trait Allocator {
fn alloc(layout: Layout, flags: Flags) -> Result<NonNull<[u8]>, AllocError> {
// SAFETY: Passing `None` to `realloc` is valid by its safety requirements and asks for a
// new memory allocation.
- unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags) }
+ unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags, None) }
+ }
+
+ /// Allocate memory based on `layout`, `flags` and `nid`.
+ ///
+ /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout
+ /// constraints (i.e. minimum size and alignment as specified by `layout`).
+ ///
+ /// This function is equivalent to `realloc` when called with `None`.
+ ///
+ /// # Guarantees
+ ///
+ /// When the return value is `Ok(ptr)`, then `ptr` is
+ /// - valid for reads and writes for `layout.size()` bytes, until it is passed to
+ /// [`Allocator::free`] or [`Allocator::realloc`],
+ /// - aligned to `layout.align()`,
+ ///
+ /// Additionally, `Flags` are honored as documented in
+ /// <https://docs.kernel.org/core-api/mm-api.html#mm-api-gfp-flags>.
+ fn alloc_node(layout: Layout, flags: Flags, nid: Option<i32>)
+ -> Result<NonNull<[u8]>, AllocError> {
+ // SAFETY: Passing `None` to `realloc` is valid by its safety requirements and asks for a
+ // new memory allocation.
+ unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags, nid) }
}
/// Re-allocate an existing memory allocation to satisfy the requested `layout`.
@@ -201,6 +224,7 @@ unsafe fn realloc(
layout: Layout,
old_layout: Layout,
flags: Flags,
+ nid: Option<i32>,
) -> Result<NonNull<[u8]>, AllocError>;
/// Free an existing memory allocation.
@@ -216,7 +240,7 @@ unsafe fn free(ptr: NonNull<u8>, layout: Layout) {
// SAFETY: The caller guarantees that `ptr` points at a valid allocation created by this
// allocator. We are passing a `Layout` with the smallest possible alignment, so it is
// smaller than or equal to the alignment previously used with this allocation.
- let _ = unsafe { Self::realloc(Some(ptr), Layout::new::<()>(), layout, Flags(0)) };
+ let _ = unsafe { Self::realloc(Some(ptr), Layout::new::<()>(), layout, Flags(0), None) };
}
}
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index aa2dfa9dca4c..91b36e128b92 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -58,7 +58,8 @@ 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) -> *mut crate::ffi::c_void,
+ unsafe extern "C" fn(*const crate::ffi::c_void, usize, usize, u32, i32)
+ -> *mut crate::ffi::c_void,
);
impl ReallocFunc {
@@ -66,7 +67,7 @@ impl ReallocFunc {
const KREALLOC: Self = Self(bindings::krealloc);
// INVARIANT: `vrealloc` satisfies the type invariants.
- const VREALLOC: Self = Self(bindings::vrealloc);
+ const VREALLOC: Self = Self(bindings::vrealloc_node);
// INVARIANT: `kvrealloc` satisfies the type invariants.
const KVREALLOC: Self = Self(bindings::kvrealloc);
@@ -87,6 +88,7 @@ unsafe fn call(
layout: Layout,
old_layout: Layout,
flags: Flags,
+ nid: Option<i32>,
) -> Result<NonNull<[u8]>, AllocError> {
let size = aligned_size(layout);
let ptr = match ptr {
@@ -100,6 +102,11 @@ unsafe fn call(
None => ptr::null(),
};
+ let c_nid = match nid {
+ None => bindings::NUMA_NO_NODE,
+ Some(n) => n,
+ };
+
// SAFETY:
// - `self.0` is one of `krealloc`, `vrealloc`, `kvrealloc` and thus only requires that
// `ptr` is NULL or valid.
@@ -110,7 +117,7 @@ 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).cast()
+ self.0(ptr.cast(), size, layout.align(), flags.0, c_nid).cast()
};
let ptr = if size == 0 {
@@ -134,9 +141,10 @@ unsafe fn realloc(
layout: Layout,
old_layout: Layout,
flags: Flags,
+ _nid: Option<i32>,
) -> Result<NonNull<[u8]>, AllocError> {
// SAFETY: `ReallocFunc::call` has the same safety requirements as `Allocator::realloc`.
- unsafe { ReallocFunc::KREALLOC.call(ptr, layout, old_layout, flags) }
+ unsafe { ReallocFunc::KREALLOC.call(ptr, layout, old_layout, flags, None) }
}
}
@@ -151,16 +159,11 @@ unsafe fn realloc(
layout: Layout,
old_layout: Layout,
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.call(ptr, layout, old_layout, flags) }
+ unsafe { ReallocFunc::VREALLOC.call(ptr, layout, old_layout, flags, nid) }
}
}
@@ -175,15 +178,18 @@ unsafe fn realloc(
layout: Layout,
old_layout: Layout,
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);
- }
+ // if the caller wants to have alignment bigger than PAGE_SIZE
+ // it's only vmalloc we can offer to satisfy that request
+ let alloc_func = if layout.align() > bindings::PAGE_SIZE {
+ ReallocFunc::VREALLOC
+ } else {
+ ReallocFunc::KVREALLOC
+ };
// SAFETY: If not `None`, `ptr` is guaranteed to point to valid memory, which was previously
// allocated with this `Allocator`.
- unsafe { ReallocFunc::KVREALLOC.call(ptr, layout, old_layout, flags) }
+ unsafe { alloc_func.call(ptr, layout, old_layout, flags, None) }
}
}
diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index 1a0dd852a468..ef4f977ba012 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -633,6 +633,7 @@ pub fn reserve(&mut self, additional: usize, flags: Flags) -> Result<(), AllocEr
layout.into(),
self.layout.into(),
flags,
+ None,
)?
};
@@ -1058,7 +1059,7 @@ pub fn collect(self, flags: Flags) -> Vec<T, A> {
// the type invariant to be smaller than `cap`. Depending on `realloc` this operation
// may shrink the buffer or leave it as it is.
ptr = match unsafe {
- A::realloc(Some(buf.cast()), layout.into(), old_layout.into(), flags)
+ A::realloc(Some(buf.cast()), layout.into(), old_layout.into(), flags, None)
} {
// If we fail to shrink, which likely can't even happen, continue with the existing
// buffer.
--
2.39.2
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