From nobody Mon Feb 9 12:29:08 2026 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D240F296BA9 for ; Fri, 23 Jan 2026 09:01:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.183 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769158865; cv=none; b=P/jSTSAWxN/dSAu0h8vNGe+3icZFfXM7HGicx1gU6odvOXbxbG9QBlOSjxT0U91HmeWQDXWZlpdo+1FYxA/BoUeYGvIV/1XK2iTUrGBrWc5pX/7FTpl/FqijT2L9M9ILv54+VS4yFI1R7MbKApGKeAY6sAOJrtY4OjZAlsHcitg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769158865; c=relaxed/simple; bh=TokOtLPJOxzGUdwmcKHQxoHBN5+zFmo6iC5kHiyYT0Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JT41PSOB/4b4G++p1LcxsKd86urE4ITDk2a/XlTbGzKT3l2qhv4qQleNicVJJY2iEQUYtJyo9f9FyPj5uqyIAW1mhwAfUOqkTs3EBENf17IRHC9pYggQ1Qi2RYtvEc8B0Jyfc78CViTjfp7kWBCEIstCkpZJRawP3Z0+vwGNSD0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=s16CndXY; arc=none smtp.client-ip=95.215.58.183 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="s16CndXY" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1769158861; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jSd5dZjazXtYLKnDww1Cz0qa7pIOMhPfOmKjHC0vcEI=; b=s16CndXYTk+3Ju3wcxjkAVQN+AwotBloPZ2BQeqwtwTfv+LXFsf84cvqam5EaIE7lkaEd8 ofv8AdNIzdVXwHkmNupiHKj8MoRrlfwN7Pew8/Tj2oC4qNitnirZER/RXQGEqLMwsS7W3y xC1vcB3c1zIqaov6OqWQX1lZ5ATaK0w= From: Hui Zhu To: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Peter Zijlstra , Miguel Ojeda , Nathan Chancellor , Kees Cook , Tejun Heo , Jeff Xu , mkoutny@suse.com, Jan Hendrik Farr , Christian Brauner , Randy Dunlap , Brian Gerst , Masahiro Yamada , davem@davemloft.net, Jakub Kicinski , Jesper Dangaard Brouer , JP Kobryn , Willem de Bruijn , Jason Xing , Paul Chaignon , Anton Protopopov , Amery Hung , Chen Ridong , Lance Yang , Jiayuan Chen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: Hui Zhu , Geliang Tang Subject: [RFC PATCH bpf-next v3 10/12] mm/bpf: Add BPF_F_ALLOW_OVERRIDE support for memcg_bpf_ops Date: Fri, 23 Jan 2026 17:00:15 +0800 Message-ID: <9f072e53f79ceaea43e3730476494517e453530a.1769157382.git.zhuhui@kylinos.cn> In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" From: Hui Zhu To allow for more flexible attachment policies in nested cgroup hierarchies, this patch introduces support for the `BPF_F_ALLOW_OVERRIDE` flag for `memcg_bpf_ops`. When a `memcg_bpf_ops` is attached to a cgroup with this flag, it permits child cgroups to attach their own, different `memcg_bpf_ops`, overriding the parent's inherited program. Without this flag, attaching a BPF program to a cgroup that already has one (either directly or via inheritance) will fail. The implementation involves: - Adding a `bpf_ops_flags` field to `struct mem_cgroup`. - During registration (`bpf_memcg_ops_reg`), checking for existing programs and the `BPF_F_ALLOW_OVERRIDE` flag. - During unregistration (`bpf_memcg_ops_unreg`), correctly restoring the parent's BPF program to the cgroup hierarchy. - Ensuring flags are inherited by child cgroups during online events. This change enables complex, multi-level policy enforcement where different subtrees of the cgroup hierarchy can have distinct memory management BPF programs. Signed-off-by: Geliang Tang Signed-off-by: Hui Zhu --- include/linux/memcontrol.h | 1 + mm/bpf_memcontrol.c | 77 ++++++++++++++++++++++++-------------- 2 files changed, 49 insertions(+), 29 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index d71e86b85ba7..a37b78d3853d 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -354,6 +354,7 @@ struct mem_cgroup { =20 #ifdef CONFIG_BPF_SYSCALL struct memcg_bpf_ops *bpf_ops; + u32 bpf_ops_flags; #endif =20 struct mem_cgroup_per_node *nodeinfo[]; diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c index 3eae1af49519..d6126b94f521 100644 --- a/mm/bpf_memcontrol.c +++ b/mm/bpf_memcontrol.c @@ -213,6 +213,7 @@ void memcontrol_bpf_online(struct mem_cgroup *memcg) goto out; =20 WRITE_ONCE(memcg->bpf_ops, ops); + memcg->bpf_ops_flags =3D parent_memcg->bpf_ops_flags; =20 /* * If the BPF program implements it, call the online handler to @@ -340,29 +341,6 @@ static int bpf_memcg_ops_init_member(const struct btf_= type *t, return 0; } =20 -/** - * clean_memcg_bpf_ops - Detach BPF programs from a cgroup hierarchy. - * @memcg: The root of the cgroup hierarchy to clean. - * @ops: The specific ops struct to detach. If NULL, detach any ops. - * - * Iterates through all descendant cgroups of @memcg (including itself) - * and clears their bpf_ops pointer. This is used when a BPF program - * is detached or if attachment fails midway. - */ -static void clean_memcg_bpf_ops(struct mem_cgroup *memcg, - struct memcg_bpf_ops *ops) -{ - struct mem_cgroup *iter =3D NULL; - - while ((iter =3D mem_cgroup_iter(memcg, iter, NULL))) { - if (ops) { - if (!WARN_ON(READ_ONCE(memcg->bpf_ops) !=3D ops)) - WRITE_ONCE(memcg->bpf_ops, NULL); - } else - WRITE_ONCE(iter->bpf_ops, NULL); - } -} - static int bpf_memcg_ops_reg(void *kdata, struct bpf_link *link) { struct bpf_struct_ops_link *ops_link @@ -371,21 +349,44 @@ static int bpf_memcg_ops_reg(void *kdata, struct bpf_= link *link) struct mem_cgroup *memcg, *iter =3D NULL; int err =3D 0; =20 + if (ops_link->flags & ~BPF_F_ALLOW_OVERRIDE) { + pr_err("attach only support BPF_F_ALLOW_OVERRIDE\n"); + return -EOPNOTSUPP; + } + memcg =3D mem_cgroup_get_from_ino(ops_link->cgroup_id); if (IS_ERR_OR_NULL(memcg)) return PTR_ERR(memcg); =20 cgroup_lock(); + + if (READ_ONCE(memcg->bpf_ops)) { + /* Check if bpf_ops of the parent is BPF_F_ALLOW_OVERRIDE. */ + if (memcg->bpf_ops_flags & BPF_F_ALLOW_OVERRIDE) { + iter =3D parent_mem_cgroup(memcg); + + if (!iter) + goto busy_out; + if (READ_ONCE(iter->bpf_ops) !=3D + READ_ONCE(memcg->bpf_ops)) + goto busy_out; + } else { +busy_out: + err =3D -EBUSY; + goto unlock_out; + } + } + while ((iter =3D mem_cgroup_iter(memcg, iter, NULL))) { if (READ_ONCE(iter->bpf_ops)) { - mem_cgroup_iter_break(memcg, iter); - err =3D -EBUSY; - break; + /* cannot override existing bpf_ops of sub-cgroup. */ + continue; } WRITE_ONCE(iter->bpf_ops, ops); + iter->bpf_ops_flags =3D ops_link->flags; } - if (err) - clean_memcg_bpf_ops(memcg, NULL); + +unlock_out: cgroup_unlock(); =20 mem_cgroup_put(memcg); @@ -399,13 +400,31 @@ static void bpf_memcg_ops_unreg(void *kdata, struct b= pf_link *link) =3D container_of(link, struct bpf_struct_ops_link, link); struct memcg_bpf_ops *ops =3D kdata; struct mem_cgroup *memcg; + struct mem_cgroup *iter; + struct memcg_bpf_ops *parent_bpf_ops =3D NULL; + u32 parent_bpf_ops_flags =3D 0; =20 memcg =3D mem_cgroup_get_from_ino(ops_link->cgroup_id); if (IS_ERR_OR_NULL(memcg)) goto out; =20 cgroup_lock(); - clean_memcg_bpf_ops(memcg, ops); + + /* Get the parent bpf_ops and bpf_ops_flags */ + iter =3D parent_mem_cgroup(memcg); + if (iter) { + parent_bpf_ops =3D READ_ONCE(iter->bpf_ops); + parent_bpf_ops_flags =3D iter->bpf_ops_flags; + } + + iter =3D NULL; + while ((iter =3D mem_cgroup_iter(memcg, iter, NULL))) { + if (READ_ONCE(iter->bpf_ops) =3D=3D ops) { + WRITE_ONCE(iter->bpf_ops, parent_bpf_ops); + iter->bpf_ops_flags =3D parent_bpf_ops_flags; + } + } + cgroup_unlock(); =20 mem_cgroup_put(memcg); --=20 2.43.0