linux-kernel - [RFC PATCH bpf-next v3 06/12] bpf: Pass flags in bpf_link_create for struct

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Message-ID: <04f5673e4b9c992a6e42ef3ea36db1df1418815f.1769157382.git.zhuhui@kylinos.cn>
Date: Fri, 23 Jan 2026 16:58:00 +0800
From: Hui Zhu <hui.zhu@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>,
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	linux-kernel@...r.kernel.org,
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Cc: Hui Zhu <zhuhui@...inos.cn>,
	Geliang Tang <geliang@...nel.org>
Subject: [RFC PATCH bpf-next v3 06/12] bpf: Pass flags in bpf_link_create for struct_ops

From: Hui Zhu <zhuhui@...inos.cn>

To support features like allowing overrides in cgroup hierarchies,
we need a way to pass flags from userspace to the kernel when
attaching a struct_ops.

Extend `bpf_struct_ops_link` to include a `flags` field. This field
is populated from `attr->link_create.flags` during link creation. This
will allow struct_ops implementations, such as the upcoming memory
controller ops, to interpret these flags and modify their attachment
behavior accordingly.

Signed-off-by: Geliang Tang <geliang@...nel.org>
Signed-off-by: Hui Zhu <zhuhui@...inos.cn>
---
 include/linux/bpf.h            | 1 +
 kernel/bpf/bpf_struct_ops.c    | 1 +
 tools/include/uapi/linux/bpf.h | 2 +-
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7c15bac782fc..b8fde3bf4b91 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1886,6 +1886,7 @@ struct bpf_struct_ops_link {
 	struct bpf_map __rcu *map;
 	wait_queue_head_t wait_hup;
 	u64 cgroup_id;
+	u32 flags;
 };
 
 struct bpf_link_primer {
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index f575c5cd0dc8..18042751f1eb 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -1390,6 +1390,7 @@ int bpf_struct_ops_link_create(union bpf_attr *attr)
 		cgroup_put(cgrp);
 	}
 #endif /* CONFIG_CGROUPS */
+	link->flags = attr->link_create.flags;
 
 	err = bpf_link_prime(&link->link, &link_primer);
 	if (err)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index b816bc53d2e1..a58fdb4484a4 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1184,7 +1184,7 @@ enum bpf_perf_event_type {
 	BPF_PERF_EVENT_EVENT = 6,
 };
 
-/* cgroup-bpf attach flags used in BPF_PROG_ATTACH command
+/* cgroup-bpf attach flags used in BPF_PROG_ATTACH and BPF_LINK_CREATE command
  *
  * NONE(default): No further bpf programs allowed in the subtree.
  *
-- 
2.43.0