From nobody Mon Feb 9 10:32:13 2026 Received: from out-171.mta0.migadu.com (out-171.mta0.migadu.com [91.218.175.171]) (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 8E205305E19; Mon, 26 Jan 2026 09:07:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769418446; cv=none; b=tXDyF9iejJjrG2f38ukpkmpeGKMTzm7esQzVsuvAXSQRUwzh4KjouwixjdG2SBp3VTJuw8Ki+jvaz28aaOEjcNBXp0y2hKwDtZEQYCPC4LL3CTOKELQwmIElEWFgUxWTk1PRGCk077GLrHXy/P6wG460GQCKMVld0HcX05k8NKg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769418446; c=relaxed/simple; bh=QbKrL9O1TZRDadE07+BX10Nasmf/eESTbhoxmYVZSYU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Q4wo6LT6H+t9sG+YHgb4C+R4YmVVjelyUFESWZrlMcZtMl8MNcU7NQaFIPyeaBSIJISj3x6PeCXvi4X/RH3wN4SBhNSgU1yppQveeQJBJ6zRx3LE0BzEqWIT1pfzkVxVzzcawk8mtDKxwRaNcEL7XpDvXqCZNtA3AxP29DMr46o= 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=lTtXD/LO; arc=none smtp.client-ip=91.218.175.171 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="lTtXD/LO" 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=1769418442; 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=k0Dc6FifkDwPpG09rd3OftsrldqK8TRlWZhlATE0DkY=; b=lTtXD/LOh3+IIxcd+dM/dMSFWAaGTq5gjHRoiDFFdavMxM7L6EGNrEf0lErtM5ghv2fBme Ip0pPMjC2i51hLQLRC/Dg2BHUOvqmmxQ5KffNQlcavmQn77TLycm+sAIeSV4UoSkeaPraa DrmsMzn84Btk59jaJ2L8npT332it7K4= 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 v4 10/12] mm/bpf: Add BPF_F_ALLOW_OVERRIDE support for memcg_bpf_ops Date: Mon, 26 Jan 2026 17:06:29 +0800 Message-ID: <443511ca5d83a01d9f7f14c9548dea41ea485aab.1769417588.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 | 83 ++++++++++++++++++++++++-------------- 2 files changed, 53 insertions(+), 31 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 1083be5d0362..6e15da44ba35 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 20c5c3552ce3..756a7d4eb4e3 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 @@ -340,52 +341,54 @@ 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(iter->bpf_ops) !=3D ops)) - WRITE_ONCE(iter->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 =3D container_of(link, struct bpf_struct_ops_link, link); - struct memcg_bpf_ops *ops =3D kdata; + struct memcg_bpf_ops *ops =3D kdata, *parent_ops =3D NULL; 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(); - while ((iter =3D mem_cgroup_iter(memcg, iter, NULL))) { - if (READ_ONCE(iter->bpf_ops)) { - mem_cgroup_iter_break(memcg, iter); + + 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 || READ_ONCE(iter->bpf_ops) !=3D + READ_ONCE(memcg->bpf_ops)) + goto busy_out; + + parent_ops =3D READ_ONCE(memcg->bpf_ops); + } else { +busy_out: err =3D -EBUSY; - break; + goto unlock_out; + } + } + + iter =3D NULL; + while ((iter =3D mem_cgroup_iter(memcg, iter, NULL))) { + struct memcg_bpf_ops *iter_ops =3D READ_ONCE(iter->bpf_ops); + + if (iter_ops && iter_ops !=3D parent_ops) { + /* 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 +402,31 @@ 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