[RFC PATCH bpf-next 05/15] bpf: Introduce helpers for container of struct bpf_map

[Yafang Shao <laoar.shao@gmail.com>]

Currently bpf_map_area_alloc() is used to allocate a container of struct
bpf_map or members in this container. To distinguish the map creation
and other members, let split it into two different helpers,
  - bpf_map_container_alloc()
    Used to allocate a container of struct bpf_map, the container is as
    follows,
      struct bpf_map_container {
        struct bpf_map map;  // the map must be the first member
        ....
      };
    Pls. note that the struct bpf_map_contianer is a abstract one, which
    can be struct bpf_array, struct bpf_bloom_filter and etc.

    In this helper, it will call bpf_map_save_memcg() to init memcg
    relevant data in the bpf map. And these data will be cleared in
    bpf_map_container_free().

  - bpf_map_area_alloc()
    Now it is used to allocate the members in a contianer only.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/bpf.h  |  4 ++++
 kernel/bpf/syscall.c | 56 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 20c26aed7896..2d971b0eb24b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1634,9 +1634,13 @@ void bpf_map_inc_with_uref(struct bpf_map *map);
 struct bpf_map * __must_check bpf_map_inc_not_zero(struct bpf_map *map);
 void bpf_map_put_with_uref(struct bpf_map *map);
 void bpf_map_put(struct bpf_map *map);
+void *bpf_map_container_alloc(u64 size, int numa_node);
+void *bpf_map_container_mmapable_alloc(u64 size, int numa_node,
+				       u32 align, u32 offset);
 void *bpf_map_area_alloc(u64 size, int numa_node);
 void *bpf_map_area_mmapable_alloc(u64 size, int numa_node);
 void bpf_map_area_free(void *base);
+void bpf_map_container_free(void *base);
 bool bpf_map_write_active(const struct bpf_map *map);
 void bpf_map_init_from_attr(struct bpf_map *map, union bpf_attr *attr);
 int  generic_map_lookup_batch(struct bpf_map *map,
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 83c7136c5788..1a1a81a11b37 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -495,6 +495,62 @@ static void bpf_map_release_memcg(struct bpf_map *map)
 }
 #endif
 
+/*
+ * The return pointer is a bpf_map container, as follow,
+ *   struct bpf_map_container {
+ *       struct bpf_map map;
+ *       ...
+ *   };
+ *
+ * It is used in map creation path.
+ */
+void *bpf_map_container_alloc(u64 size, int numa_node)
+{
+	struct bpf_map *map;
+	void *container;
+
+	container = __bpf_map_area_alloc(size, numa_node, false);
+	if (!container)
+		return NULL;
+
+	map = (struct bpf_map *)container;
+	bpf_map_save_memcg(map);
+
+	return container;
+}
+
+void *bpf_map_container_mmapable_alloc(u64 size, int numa_node, u32 align,
+				       u32 offset)
+{
+	struct bpf_map *map;
+	void *container;
+	void *ptr;
+
+	/* kmalloc'ed memory can't be mmap'ed, use explicit vmalloc */
+	ptr = __bpf_map_area_alloc(size, numa_node, true);
+	if (!ptr)
+		return NULL;
+
+	container = ptr + align - offset;
+	map = (struct bpf_map *)container;
+	bpf_map_save_memcg(map);
+
+	return ptr;
+}
+
+void bpf_map_container_free(void *container)
+{
+	struct bpf_map *map;
+
+	if (!container)
+		return;
+
+	map = (struct bpf_map *)container;
+	bpf_map_release_memcg(map);
+
+	kvfree(container);
+}
+
 static int bpf_map_kptr_off_cmp(const void *a, const void *b)
 {
 	const struct bpf_map_value_off_desc *off_desc1 = a, *off_desc2 = b;
-- 
2.17.1