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.

Link: https://lkml.kernel.org/r/20250806125552.1727073-1-vitaly.wool@konsulko.se
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Alice Ryhl <aliceryhl@google.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Jann Horn <jannh@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

3 files changed, 18 insertions, 27 deletions

diff --git a/rust/helpers/slab.c b/rust/helpers/slab.c
index 8472370a4338..7fac958907b0 100644
--- a/rust/helpers/slab.c
+++ b/rust/helpers/slab.c
@@ -3,13 +3,15 @@
 #include <linux/slab.h>
 
 void * __must_check __realloc_size(2)
-rust_helper_krealloc_node(const void *objp, size_t new_size, gfp_t flags, int node)
+rust_helper_krealloc_node_align(const void *objp, size_t new_size, unsigned long align,
+				gfp_t flags, int node)
 {
-	return krealloc_node(objp, new_size, flags, node);
+	return krealloc_node_align(objp, new_size, align, flags, node);
 }
 
 void * __must_check __realloc_size(2)
-rust_helper_kvrealloc_node(const void *p, size_t size, gfp_t flags, int node)
+rust_helper_kvrealloc_node_align(const void *p, size_t size, unsigned long align,
+				 gfp_t flags, int node)
 {
-	return kvrealloc_node(p, size, flags, node);
+	return kvrealloc_node_align(p, size, align, flags, node);
 }
diff --git a/rust/helpers/vmalloc.c b/rust/helpers/vmalloc.c
index 62d30db9a1a6..7d7f7336b3d2 100644
--- a/rust/helpers/vmalloc.c
+++ b/rust/helpers/vmalloc.c
@@ -3,7 +3,8 @@
 #include <linux/vmalloc.h>
 
 void * __must_check __realloc_size(2)
-rust_helper_vrealloc_node(const void *p, size_t size, gfp_t flags, int node)
+rust_helper_vrealloc_node_align(const void *p, size_t size, unsigned long align,
+				gfp_t flags, int node)
 {
-	return vrealloc_node(p, size, flags, 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 14510a9e4502..f4ae0cf0a594 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -15,7 +15,6 @@ use core::ptr::NonNull;
 
 use crate::alloc::{AllocError, Allocator, NumaNode};
 use crate::bindings;
-use crate::pr_warn;
 
 /// The contiguous kernel allocator.
 ///
@@ -45,25 +44,26 @@ pub struct KVmalloc;
 
 /// # Invariants
 ///
-/// One of the following: `krealloc_node`, `vrealloc_node`, `kvrealloc_node`.
+/// One of the following: `krealloc_node_align`, `vrealloc_node_align`, `kvrealloc_node_align`.
 struct ReallocFunc(
     unsafe extern "C" fn(
         *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: Self = Self(bindings::krealloc_node);
+    // INVARIANT: `krealloc_node_align` satisfies the type invariants.
+    const KREALLOC: Self = Self(bindings::krealloc_node_align);
 
-    // INVARIANT: `vrealloc_node` satisfies the type invariants.
-    const VREALLOC: Self = Self(bindings::vrealloc_node);
+    // INVARIANT: `vrealloc_node_align` satisfies the type invariants.
+    const VREALLOC: Self = Self(bindings::vrealloc_node_align);
 
-    // INVARIANT: `kvrealloc_node` satisfies the type invariants.
-    const KVREALLOC: Self = Self(bindings::kvrealloc_node);
+    // INVARIANT: `kvrealloc_node_align` satisfies the type invariants.
+    const KVREALLOC: Self = Self(bindings::kvrealloc_node_align);
 
     /// # Safety
     ///
@@ -105,7 +105,7 @@ impl ReallocFunc {
         // - 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, nid.0).cast()
+            self.0(ptr.cast(), size, layout.align(), flags.0, nid.0).cast()
         };
 
         let ptr = if size == 0 {
@@ -162,12 +162,6 @@ unsafe impl Allocator for Vmalloc {
         flags: Flags,
         nid: NumaNode,
     ) -> 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, nid) }
@@ -191,12 +185,6 @@ unsafe impl Allocator for KVmalloc {
         // 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");
-            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.call(ptr, layout, old_layout, flags, nid) }