linux-kernel - [PATCH v2 02/23] bpf: initial support for attaching struct ops to cgroups

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Message-ID: <20251027231727.472628-3-roman.gushchin@linux.dev>
Date: Mon, 27 Oct 2025 16:17:05 -0700
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
	Alexei Starovoitov <ast@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...nel.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	JP Kobryn <inwardvessel@...il.com>,
	linux-mm@...ck.org,
	cgroups@...r.kernel.org,
	bpf@...r.kernel.org,
	Martin KaFai Lau <martin.lau@...nel.org>,
	Song Liu <song@...nel.org>,
	Kumar Kartikeya Dwivedi <memxor@...il.com>,
	Tejun Heo <tj@...nel.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>
Subject: [PATCH v2 02/23] bpf: initial support for attaching struct ops to cgroups

When a struct ops is being attached and a bpf link is created,
allow to pass a cgroup fd using bpf attr, so that struct ops
can be attached to a cgroup instead of globally.

Attached struct ops doesn't hold a reference to the cgroup,
only preserves cgroup id.

Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
---
 include/linux/bpf.h         |  1 +
 kernel/bpf/bpf_struct_ops.c | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index eae907218188..7205b813e25f 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1849,6 +1849,7 @@ struct bpf_struct_ops_link {
 	struct bpf_link link;
 	struct bpf_map __rcu *map;
 	wait_queue_head_t wait_hup;
+	u64 cgroup_id;
 };
 
 struct bpf_link_primer {
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 45cc5ee19dc2..58664779a2b6 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -13,6 +13,7 @@
 #include <linux/btf_ids.h>
 #include <linux/rcupdate_wait.h>
 #include <linux/poll.h>
+#include <linux/cgroup.h>
 
 struct bpf_struct_ops_value {
 	struct bpf_struct_ops_common_value common;
@@ -1359,6 +1360,18 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
 	}
 	bpf_link_init(&link->link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_map_lops, NULL,
 		      attr->link_create.attach_type);
+#ifdef CONFIG_CGROUPS
+	if (attr->link_create.cgroup.relative_fd) {
+		struct cgroup *cgrp;
+
+		cgrp = cgroup_get_from_fd(attr->link_create.cgroup.relative_fd);
+		if (IS_ERR(cgrp))
+			return PTR_ERR(cgrp);
+
+		link->cgroup_id = cgroup_id(cgrp);
+		cgroup_put(cgrp);
+	}
+#endif /* CONFIG_CGROUPS */
 
 	err = bpf_link_prime(&link->link, &link_primer);
 	if (err)
-- 
2.51.0