From: Roman Gushchin <guro@fb.com>
Date: Thu, 2 Aug 2018 14:27:17 -0700
Subject: bpf: add ability to charge bpf maps memory dynamically
Patch-mainline: v4.19-rc1
Git-commit: 0a4c58f5702858822621fa1177c7d3475f181ccb
References: bsc#1109837

This commits extends existing bpf maps memory charging API
to support dynamic charging/uncharging.

This is required to account memory used by maps,
if all entries are created dynamically after
the map initialization.

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/linux/bpf.h  |    2 +
 kernel/bpf/syscall.c |   58 +++++++++++++++++++++++++++++++++++++--------------
 2 files changed, 45 insertions(+), 15 deletions(-)

--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -429,6 +429,8 @@ struct bpf_map * __must_check bpf_map_in
 void bpf_map_put_with_uref(struct bpf_map *map);
 void bpf_map_put(struct bpf_map *map);
 int bpf_map_precharge_memlock(u32 pages);
+int bpf_map_charge_memlock(struct bpf_map *map, u32 pages);
+void bpf_map_uncharge_memlock(struct bpf_map *map, u32 pages);
 void *bpf_map_area_alloc(size_t size, int numa_node);
 void bpf_map_area_free(void *base);
 void bpf_map_init_from_attr(struct bpf_map *map, union bpf_attr *attr);
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -178,32 +178,60 @@ int bpf_map_precharge_memlock(u32 pages)
 	return 0;
 }
 
-static int bpf_map_charge_memlock(struct bpf_map *map)
+static int bpf_charge_memlock(struct user_struct *user, u32 pages)
 {
-	struct user_struct *user = get_current_user();
-	unsigned long memlock_limit;
+	unsigned long memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+
+	if (atomic_long_add_return(pages, &user->locked_vm) > memlock_limit) {
+		atomic_long_sub(pages, &user->locked_vm);
+		return -EPERM;
+	}
+	return 0;
+}
 
-	memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+static void bpf_uncharge_memlock(struct user_struct *user, u32 pages)
+{
+	atomic_long_sub(pages, &user->locked_vm);
+}
 
-	atomic_long_add(map->pages, &user->locked_vm);
+static int bpf_map_init_memlock(struct bpf_map *map)
+{
+	struct user_struct *user = get_current_user();
+	int ret;
 
-	if (atomic_long_read(&user->locked_vm) > memlock_limit) {
-		atomic_long_sub(map->pages, &user->locked_vm);
+	ret = bpf_charge_memlock(user, map->pages);
+	if (ret) {
 		free_uid(user);
-		return -EPERM;
+		return ret;
 	}
 	map->user = user;
-	return 0;
+	return ret;
 }
 
-static void bpf_map_uncharge_memlock(struct bpf_map *map)
+static void bpf_map_release_memlock(struct bpf_map *map)
 {
 	struct user_struct *user = map->user;
-
-	atomic_long_sub(map->pages, &user->locked_vm);
+	bpf_uncharge_memlock(user, map->pages);
 	free_uid(user);
 }
 
+int bpf_map_charge_memlock(struct bpf_map *map, u32 pages)
+{
+	int ret;
+
+	ret = bpf_charge_memlock(map->user, pages);
+	if (ret)
+		return ret;
+	map->pages += pages;
+	return ret;
+}
+
+void bpf_map_uncharge_memlock(struct bpf_map *map, u32 pages)
+{
+	bpf_uncharge_memlock(map->user, pages);
+	map->pages -= pages;
+}
+
 static int bpf_map_alloc_id(struct bpf_map *map)
 {
 	int id;
@@ -253,7 +281,7 @@ static void bpf_map_free_deferred(struct
 {
 	struct bpf_map *map = container_of(work, struct bpf_map, work);
 
-	bpf_map_uncharge_memlock(map);
+	bpf_map_release_memlock(map);
 	/* implementation dependent freeing */
 	map->ops->map_free(map);
 }
@@ -478,7 +506,7 @@ static int map_create(union bpf_attr *at
 		map->btf_value_type_id = attr->btf_value_type_id;
 	}
 
-	err = bpf_map_charge_memlock(map);
+	err = bpf_map_init_memlock(map);
 	if (err)
 		goto free_map_nouncharge;
 
@@ -501,7 +529,7 @@ static int map_create(union bpf_attr *at
 	return err;
 
 free_map:
-	bpf_map_uncharge_memlock(map);
+	bpf_map_release_memlock(map);
 free_map_nouncharge:
 	btf_put(map->btf);
 	map->ops->map_free(map);