rust: alloc: implement `KVmalloc` allocator

Implement `Allocator` for `KVmalloc`, an `Allocator` that tries to
allocate memory with `kmalloc` first and, on failure, falls back to
`vmalloc`.

All memory allocations made with `KVmalloc` end up in
`kvrealloc_noprof()`; all frees in `kvfree()`.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241004154149.93856-10-dakr@kernel.org
[ Reworded typo. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/rust/helpers/slab.c b/rust/helpers/slab.c
index f043e087f9d6..a842bfbddcba 100644
--- a/rust/helpers/slab.c
+++ b/rust/helpers/slab.c
@@ -7,3 +7,9 @@ rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags)
 {
 	return krealloc(objp, new_size, flags);
 }
+
+void * __must_check __realloc_size(2)
+rust_helper_kvrealloc(const void *p, size_t size, gfp_t flags)
+{
+	return kvrealloc(p, size, flags);
+}