Merge branch 'mm-bpf-kfuncs-to-access-memcg-data'

Roman Gushchin says:

====================
mm: bpf kfuncs to access memcg data

Introduce kfuncs to simplify the access to the memcg data.
These kfuncs can be used to accelerate monitoring use cases and
for implementing custom OOM policies once BPF OOM is landed.

This patchset was separated out from the BPF OOM patchset to simplify
the logistics and accelerate the landing of the part which is useful
by itself. No functional changes since BPF OOM v2.

v4:
  - refactored memcg vm event and stat item idx checks (by Alexei)

v3:
  - dropped redundant kfuncs flags (by Alexei)
  - fixed kdocs warnings (by Alexei)
  - merged memcg stats access patches into one (by Alexei)
  - restored root memcg usage reporting, added a comment
  - added checks for enum boundaries
  - added Shakeel and JP as co-maintainers (by Shakeel)

v2:
  - added mem_cgroup_disabled() checks (by Shakeel B.)
  - added special handling of the root memcg in bpf_mem_cgroup_usage()
  (by Shakeel B.)
  - minor fixes in the kselftest (by Shakeel B.)
  - added a MAINTAINERS entry (by Shakeel B.)

v1:
  https://lore.kernel.org/bpf/87ike29s5r.fsf@linux.dev/T/#t
====================

Link: https://patch.msgid.link/20251223044156.208250-1-roman.gushchin@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

9 files changed, 521 insertions, 1 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index e7027fba97db..70c2b73b3941 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4799,6 +4799,15 @@ L:	bpf@vger.kernel.org
 S:	Maintained
 F:	tools/lib/bpf/
 
+BPF [MEMORY MANAGEMENT EXTENSIONS]
+M:	Roman Gushchin <roman.gushchin@linux.dev>
+M:	JP Kobryn <inwardvessel@gmail.com>
+M:	Shakeel Butt <shakeel.butt@linux.dev>
+L:	bpf@vger.kernel.org
+L:	linux-mm@kvack.org
+S:	Maintained
+F:	mm/bpf_memcontrol.c
+
 BPF [MISC]
 L:	bpf@vger.kernel.org
 S:	Odd Fixes
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 0651865a4564..6a5d65487b70 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -949,7 +949,12 @@ static inline void mod_memcg_page_state(struct page *page,
 	rcu_read_unlock();
 }
 
+unsigned long memcg_events(struct mem_cgroup *memcg, int event);
+unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap);
 unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx);
+unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item);
+bool memcg_stat_item_valid(int idx);
+bool memcg_vm_event_item_valid(enum vm_event_item idx);
 unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx);
 unsigned long lruvec_page_state_local(struct lruvec *lruvec,
 				      enum node_stat_item idx);
@@ -1373,6 +1378,21 @@ static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
 	return 0;
 }
 
+static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item)
+{
+	return 0;
+}
+
+static inline bool memcg_stat_item_valid(int idx)
+{
+	return false;
+}
+
+static inline bool memcg_vm_event_item_valid(enum vm_event_item idx)
+{
+	return false;
+}
+
 static inline unsigned long lruvec_page_state(struct lruvec *lruvec,
 					      enum node_stat_item idx)
 {
diff --git a/mm/Makefile b/mm/Makefile
index 2d0570a16e5b..bf46fe31dc14 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -106,6 +106,9 @@ obj-$(CONFIG_MEMCG) += memcontrol.o vmpressure.o
 ifdef CONFIG_SWAP
 obj-$(CONFIG_MEMCG) += swap_cgroup.o
 endif
+ifdef CONFIG_BPF_SYSCALL
+obj-$(CONFIG_MEMCG) += bpf_memcontrol.o
+endif
 obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o
 obj-$(CONFIG_GUP_TEST) += gup_test.o
 obj-$(CONFIG_DMAPOOL_TEST) += dmapool_test.o
diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c
new file mode 100644
index 000000000000..e8fa7f5855f9
--- /dev/null
+++ b/mm/bpf_memcontrol.c
@@ -0,0 +1,193 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Memory Controller-related BPF kfuncs and auxiliary code
+ *
+ * Author: Roman Gushchin <roman.gushchin@linux.dev>
+ */
+
+#include <linux/memcontrol.h>
+#include <linux/bpf.h>
+
+__bpf_kfunc_start_defs();
+
+/**
+ * bpf_get_root_mem_cgroup - Returns a pointer to the root memory cgroup
+ *
+ * The function has KF_ACQUIRE semantics, even though the root memory
+ * cgroup is never destroyed after being created and doesn't require
+ * reference counting. And it's perfectly safe to pass it to
+ * bpf_put_mem_cgroup()
+ *
+ * Return: A pointer to the root memory cgroup.
+ */
+__bpf_kfunc struct mem_cgroup *bpf_get_root_mem_cgroup(void)
+{
+	if (mem_cgroup_disabled())
+		return NULL;
+
+	/* css_get() is not needed */
+	return root_mem_cgroup;
+}
+
+/**
+ * bpf_get_mem_cgroup - Get a reference to a memory cgroup
+ * @css: pointer to the css structure
+ *
+ * It's fine to pass a css which belongs to any cgroup controller,
+ * e.g. unified hierarchy's main css.
+ *
+ * Implements KF_ACQUIRE semantics.
+ *
+ * Return: A pointer to a mem_cgroup structure after bumping
+ * the corresponding css's reference counter.
+ */
+__bpf_kfunc struct mem_cgroup *
+bpf_get_mem_cgroup(struct cgroup_subsys_state *css)
+{
+	struct mem_cgroup *memcg = NULL;
+	bool rcu_unlock = false;
+
+	if (mem_cgroup_disabled() || !root_mem_cgroup)
+		return NULL;
+
+	if (root_mem_cgroup->css.ss != css->ss) {
+		struct cgroup *cgroup = css->cgroup;
+		int ssid = root_mem_cgroup->css.ss->id;
+
+		rcu_read_lock();
+		rcu_unlock = true;
+		css = rcu_dereference_raw(cgroup->subsys[ssid]);
+	}
+
+	if (css && css_tryget(css))
+		memcg = container_of(css, struct mem_cgroup, css);
+
+	if (rcu_unlock)
+		rcu_read_unlock();
+
+	return memcg;
+}
+
+/**
+ * bpf_put_mem_cgroup - Put a reference to a memory cgroup
+ * @memcg: memory cgroup to release
+ *
+ * Releases a previously acquired memcg reference.
+ * Implements KF_RELEASE semantics.
+ */
+__bpf_kfunc void bpf_put_mem_cgroup(struct mem_cgroup *memcg)
+{
+	css_put(&memcg->css);
+}
+
+/**
+ * bpf_mem_cgroup_vm_events - Read memory cgroup's vm event counter
+ * @memcg: memory cgroup
+ * @event: event id
+ *
+ * Allows to read memory cgroup event counters.
+ *
+ * Return: The current value of the corresponding events counter.
+ */
+__bpf_kfunc unsigned long bpf_mem_cgroup_vm_events(struct mem_cgroup *memcg,
+						   enum vm_event_item event)
+{
+	if (unlikely(!memcg_vm_event_item_valid(event)))
+		return (unsigned long)-1;
+
+	return memcg_events(memcg, event);
+}
+
+/**
+ * bpf_mem_cgroup_usage - Read memory cgroup's usage
+ * @memcg: memory cgroup
+ *
+ * Please, note that the root memory cgroup it special and is exempt
+ * from the memory accounting. The returned value is a sum of sub-cgroup's
+ * usages and it not reflecting the size of the root memory cgroup itself.
+ * If you need to get an approximation, you can use root level statistics:
+ * e.g. NR_FILE_PAGES + NR_ANON_MAPPED.
+ *
+ * Return: The current memory cgroup size in bytes.
+ */
+__bpf_kfunc unsigned long bpf_mem_cgroup_usage(struct mem_cgroup *memcg)
+{
+	return page_counter_read(&memcg->memory) * PAGE_SIZE;
+}
+
+/**
+ * bpf_mem_cgroup_memory_events - Read memory cgroup's memory event value
+ * @memcg: memory cgroup
+ * @event: memory event id
+ *
+ * Return: The current value of the memory event counter.
+ */
+__bpf_kfunc unsigned long bpf_mem_cgroup_memory_events(struct mem_cgroup *memcg,
+						       enum memcg_memory_event event)
+{
+	if (unlikely(event >= MEMCG_NR_MEMORY_EVENTS))
+		return (unsigned long)-1;
+
+	return atomic_long_read(&memcg->memory_events[event]);
+}
+
+/**
+ * bpf_mem_cgroup_page_state - Read memory cgroup's page state counter
+ * @memcg: memory cgroup
+ * @idx: counter idx
+ *
+ * Allows to read memory cgroup statistics. The output is in bytes.
+ *
+ * Return: The value of the page state counter in bytes.
+ */
+__bpf_kfunc unsigned long bpf_mem_cgroup_page_state(struct mem_cgroup *memcg, int idx)
+{
+	if (unlikely(!memcg_stat_item_valid(idx)))
+		return (unsigned long)-1;
+
+	return memcg_page_state_output(memcg, idx);
+}
+
+/**
+ * bpf_mem_cgroup_flush_stats - Flush memory cgroup's statistics
+ * @memcg: memory cgroup
+ *
+ * Propagate memory cgroup's statistics up the cgroup tree.
+ */
+__bpf_kfunc void bpf_mem_cgroup_flush_stats(struct mem_cgroup *memcg)
+{
+	mem_cgroup_flush_stats(memcg);
+}
+
+__bpf_kfunc_end_defs();
+
+BTF_KFUNCS_START(bpf_memcontrol_kfuncs)
+BTF_ID_FLAGS(func, bpf_get_root_mem_cgroup, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_get_mem_cgroup, KF_ACQUIRE | KF_RET_NULL | KF_RCU)
+BTF_ID_FLAGS(func, bpf_put_mem_cgroup, KF_RELEASE)
+
+BTF_ID_FLAGS(func, bpf_mem_cgroup_vm_events, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_mem_cgroup_memory_events, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_mem_cgroup_usage, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_mem_cgroup_page_state, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_mem_cgroup_flush_stats, KF_TRUSTED_ARGS | KF_SLEEPABLE)
+
+BTF_KFUNCS_END(bpf_memcontrol_kfuncs)
+
+static const struct btf_kfunc_id_set bpf_memcontrol_kfunc_set = {
+	.owner          = THIS_MODULE,
+	.set            = &bpf_memcontrol_kfuncs,
+};
+
+static int __init bpf_memcontrol_init(void)
+{
+	int err;
+
+	err = register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC,
+					&bpf_memcontrol_kfunc_set);
+	if (err)
+		pr_warn("error while registering bpf memcontrol kfuncs: %d", err);
+
+	return err;
+}
+late_initcall(bpf_memcontrol_init);
diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h
index 6358464bb416..a304ad418cdf 100644
--- a/mm/memcontrol-v1.h
+++ b/mm/memcontrol-v1.h
@@ -27,7 +27,6 @@ unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap);
 void drain_all_stock(struct mem_cgroup *root_memcg);
 
 unsigned long memcg_events(struct mem_cgroup *memcg, int event);
-unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item);
 int memory_stat_show(struct seq_file *m, void *v);
 
 void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index be810c1fbfc3..bae4eb72da61 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -663,6 +663,14 @@ unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
 	return x;
 }
 
+bool memcg_stat_item_valid(int idx)
+{
+	if ((u32)idx >= MEMCG_NR_STAT)
+		return false;
+
+	return !BAD_STAT_IDX(memcg_stats_index(idx));
+}
+
 static int memcg_page_state_unit(int item);
 
 /*
@@ -860,6 +868,14 @@ unsigned long memcg_events(struct mem_cgroup *memcg, int event)
 	return READ_ONCE(memcg->vmstats->events[i]);
 }
 
+bool memcg_vm_event_item_valid(enum vm_event_item idx)
+{
+	if (idx >= NR_VM_EVENT_ITEMS)
+		return false;
+
+	return !BAD_STAT_IDX(memcg_events_index(idx));
+}
+
 #ifdef CONFIG_MEMCG_V1
 unsigned long memcg_events_local(struct mem_cgroup *memcg, int event)
 {
diff --git a/tools/testing/selftests/bpf/cgroup_iter_memcg.h b/tools/testing/selftests/bpf/cgroup_iter_memcg.h
new file mode 100644
index 000000000000..3f59b127943b
--- /dev/null
+++ b/tools/testing/selftests/bpf/cgroup_iter_memcg.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#ifndef __CGROUP_ITER_MEMCG_H
+#define __CGROUP_ITER_MEMCG_H
+
+struct memcg_query {
+	/* some node_stat_item's */
+	unsigned long nr_anon_mapped;
+	unsigned long nr_shmem;
+	unsigned long nr_file_pages;
+	unsigned long nr_file_mapped;
+	/* some memcg_stat_item */
+	unsigned long memcg_kmem;
+	/* some vm_event_item */
+	unsigned long pgfault;
+};
+
+#endif /* __CGROUP_ITER_MEMCG_H */
diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c b/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c
new file mode 100644
index 000000000000..a5afd16705f0
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_iter_memcg.c
@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include <bpf/libbpf.h>
+#include <bpf/btf.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include "cgroup_helpers.h"
+#include "cgroup_iter_memcg.h"
+#include "cgroup_iter_memcg.skel.h"
+
+static int read_stats(struct bpf_link *link)
+{
+	int fd, ret = 0;
+	ssize_t bytes;
+
+	fd = bpf_iter_create(bpf_link__fd(link));
+	if (!ASSERT_OK_FD(fd, "bpf_iter_create"))
+		return 1;
+
+	/*
+	 * Invoke iter program by reading from its fd. We're not expecting any
+	 * data to be written by the bpf program so the result should be zero.
+	 * Results will be read directly through the custom data section
+	 * accessible through skel->data_query.memcg_query.
+	 */
+	bytes = read(fd, NULL, 0);
+	if (!ASSERT_EQ(bytes, 0, "read fd"))
+		ret = 1;
+
+	close(fd);
+	return ret;
+}
+
+static void test_anon(struct bpf_link *link, struct memcg_query *memcg_query)
+{
+	void *map;
+	size_t len;
+
+	len = sysconf(_SC_PAGESIZE) * 1024;
+
+	/*
+	 * Increase memcg anon usage by mapping and writing
+	 * to a new anon region.
+	 */
+	map = mmap(NULL, len, PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (!ASSERT_NEQ(map, MAP_FAILED, "mmap anon"))
+		return;
+
+	memset(map, 1, len);
+
+	if (!ASSERT_OK(read_stats(link), "read stats"))
+		goto cleanup;
+
+	ASSERT_GT(memcg_query->nr_anon_mapped, 0, "final anon mapped val");
+
+cleanup:
+	munmap(map, len);
+}
+
+static void test_file(struct bpf_link *link, struct memcg_query *memcg_query)
+{
+	void *map;
+	size_t len;
+	char *path;
+	int fd;
+
+	len = sysconf(_SC_PAGESIZE) * 1024;
+	path = "/tmp/test_cgroup_iter_memcg";
+
+	/*
+	 * Increase memcg file usage by creating and writing
+	 * to a mapped file.
+	 */
+	fd = open(path, O_CREAT | O_RDWR, 0644);
+	if (!ASSERT_OK_FD(fd, "open fd"))
+		return;
+	if (!ASSERT_OK(ftruncate(fd, len), "ftruncate"))
+		goto cleanup_fd;
+
+	map = mmap(NULL, len, PROT_WRITE, MAP_SHARED, fd, 0);
+	if (!ASSERT_NEQ(map, MAP_FAILED, "mmap file"))
+		goto cleanup_fd;
+
+	memset(map, 1, len);
+
+	if (!ASSERT_OK(read_stats(link), "read stats"))
+		goto cleanup_map;
+
+	ASSERT_GT(memcg_query->nr_file_pages, 0, "final file value");
+	ASSERT_GT(memcg_query->nr_file_mapped, 0, "final file mapped value");
+
+cleanup_map:
+	munmap(map, len);
+cleanup_fd:
+	close(fd);
+	unlink(path);
+}
+
+static void test_shmem(struct bpf_link *link, struct memcg_query *memcg_query)
+{
+	size_t len;
+	int fd;
+
+	len = sysconf(_SC_PAGESIZE) * 1024;
+
+	/*
+	 * Increase memcg shmem usage by creating and writing
+	 * to a shmem object.
+	 */
+	fd = shm_open("/tmp_shmem", O_CREAT | O_RDWR, 0644);
+	if (!ASSERT_OK_FD(fd, "shm_open"))
+		return;
+
+	if (!ASSERT_OK(fallocate(fd, 0, 0, len), "fallocate"))
+		goto cleanup;
+
+	if (!ASSERT_OK(read_stats(link), "read stats"))
+		goto cleanup;
+
+	ASSERT_GT(memcg_query->nr_shmem, 0, "final shmem value");
+
+cleanup:
+	close(fd);
+	shm_unlink("/tmp_shmem");
+}
+
+#define NR_PIPES 64
+static void test_kmem(struct bpf_link *link, struct memcg_query *memcg_query)
+{
+	int fds[NR_PIPES][2], i;
+
+	/*
+	 * Increase kmem value by creating pipes which will allocate some
+	 * kernel buffers.
+	 */
+	for (i = 0; i < NR_PIPES; i++) {
+		if (!ASSERT_OK(pipe(fds[i]), "pipe"))
+			goto cleanup;
+	}
+
+	if (!ASSERT_OK(read_stats(link), "read stats"))
+		goto cleanup;
+
+	ASSERT_GT(memcg_query->memcg_kmem, 0, "kmem value");
+
+cleanup:
+	for (i = i - 1; i >= 0; i--) {
+		close(fds[i][0]);
+		close(fds[i][1]);
+	}
+}
+
+static void test_pgfault(struct bpf_link *link, struct memcg_query *memcg_query)
+{
+	void *map;
+	size_t len;
+
+	len = sysconf(_SC_PAGESIZE) * 1024;
+
+	/* Create region to use for triggering a page fault. */
+	map = mmap(NULL, len, PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (!ASSERT_NEQ(map, MAP_FAILED, "mmap anon"))
+		return;
+
+	/* Trigger page fault. */
+	memset(map, 1, len);
+
+	if (!ASSERT_OK(read_stats(link), "read stats"))
+		goto cleanup;
+
+	ASSERT_GT(memcg_query->pgfault, 0, "final pgfault val");
+
+cleanup:
+	munmap(map, len);
+}
+
+void test_cgroup_iter_memcg(void)
+{
+	char *cgroup_rel_path = "/cgroup_iter_memcg_test";
+	struct cgroup_iter_memcg *skel;
+	struct bpf_link *link;
+	int cgroup_fd;
+
+	cgroup_fd = cgroup_setup_and_join(cgroup_rel_path);
+	if (!ASSERT_OK_FD(cgroup_fd, "cgroup_setup_and_join"))
+		return;
+
+	skel = cgroup_iter_memcg__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "cgroup_iter_memcg__open_and_load"))
+		goto cleanup_cgroup_fd;
+
+	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+	union bpf_iter_link_info linfo = {
+		.cgroup.cgroup_fd = cgroup_fd,
+		.cgroup.order = BPF_CGROUP_ITER_SELF_ONLY,
+	};
+	opts.link_info = &linfo;
+	opts.link_info_len = sizeof(linfo);
+
+	link = bpf_program__attach_iter(skel->progs.cgroup_memcg_query, &opts);
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach_iter"))
+		goto cleanup_skel;
+
+	if (test__start_subtest("cgroup_iter_memcg__anon"))
+		test_anon(link, &skel->data_query->memcg_query);
+	if (test__start_subtest("cgroup_iter_memcg__shmem"))
+		test_shmem(link, &skel->data_query->memcg_query);
+	if (test__start_subtest("cgroup_iter_memcg__file"))
+		test_file(link, &skel->data_query->memcg_query);
+	if (test__start_subtest("cgroup_iter_memcg__kmem"))
+		test_kmem(link, &skel->data_query->memcg_query);
+	if (test__start_subtest("cgroup_iter_memcg__pgfault"))
+		test_pgfault(link, &skel->data_query->memcg_query);
+
+	bpf_link__destroy(link);
+cleanup_skel:
+	cgroup_iter_memcg__destroy(skel);
+cleanup_cgroup_fd:
+	close(cgroup_fd);
+	cleanup_cgroup_environment();
+}
diff --git a/tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c b/tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c
new file mode 100644
index 000000000000..59fb70a3cc50
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/cgroup_iter_memcg.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_core_read.h>
+#include "cgroup_iter_memcg.h"
+
+char _license[] SEC("license") = "GPL";
+
+/* The latest values read are stored here. */
+struct memcg_query memcg_query SEC(".data.query");
+
+SEC("iter.s/cgroup")
+int cgroup_memcg_query(struct bpf_iter__cgroup *ctx)
+{
+	struct cgroup *cgrp = ctx->cgroup;
+	struct cgroup_subsys_state *css;
+	struct mem_cgroup *memcg;
+
+	if (!cgrp)
+		return 1;
+
+	css = &cgrp->self;
+	memcg = bpf_get_mem_cgroup(css);
+	if (!memcg)
+		return 1;
+
+	bpf_mem_cgroup_flush_stats(memcg);
+
+	memcg_query.nr_anon_mapped = bpf_mem_cgroup_page_state(memcg, NR_ANON_MAPPED);
+	memcg_query.nr_shmem = bpf_mem_cgroup_page_state(memcg, NR_SHMEM);
+	memcg_query.nr_file_pages = bpf_mem_cgroup_page_state(memcg, NR_FILE_PAGES);
+	memcg_query.nr_file_mapped = bpf_mem_cgroup_page_state(memcg, NR_FILE_MAPPED);
+	memcg_query.memcg_kmem = bpf_mem_cgroup_page_state(memcg, MEMCG_KMEM);
+	memcg_query.pgfault = bpf_mem_cgroup_vm_events(memcg, PGFAULT);
+
+	bpf_put_mem_cgroup(memcg);
+
+	return 0;
+}