From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BDC1CCCF9E5 for ; Mon, 27 Oct 2025 23:18:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 268AF800B0; Mon, 27 Oct 2025 19:18:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 218468009B; Mon, 27 Oct 2025 19:18:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0E02A800B0; Mon, 27 Oct 2025 19:18:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id EB7208009B for ; Mon, 27 Oct 2025 19:18:14 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id B663113A259 for ; Mon, 27 Oct 2025 23:18:14 +0000 (UTC) X-FDA: 84045459708.17.CD3A583 Received: from out-171.mta1.migadu.com (out-171.mta1.migadu.com [95.215.58.171]) by imf25.hostedemail.com (Postfix) with ESMTP id 0C097A0008 for ; Mon, 27 Oct 2025 23:18:12 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=w5UMrwUa; spf=pass (imf25.hostedemail.com: domain of roman.gushchin@linux.dev designates 95.215.58.171 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1761607093; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=1pBvFLnmQUGhHDldbyfAqGwleevT81Px3hvXcQya18A=; b=3/3Y38CTdQnKKq4K4xa0koEOGHkLJmnN7WPnAgmnLDYLgvHgQOQVk6jiA/hBlNPbQei5z5 XbtoD412x9ty+du1Y0vX73GZHz9HlUoiirfgBJfpjiDT4Q74hjGEzc2EzDMgQuXD+SrsJq VVLgWr4wW6YIObJ2cs+0TTlL1d+Afjw= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1761607093; a=rsa-sha256; cv=none; b=tUD42dbA7qBSTcJw+GFmPRwd/duufEhIVsHFye7R29IL/hBvLp7cOkYXxQM7YAEsfCED05 6xaEERlRR4j+XbiXm628FciOwDIS+tHIruJ5FN3qfVnN8uO5NnNn7L2u7SCald68FBGHTR EUeKpAGK2ZBofWET+5SrBJQaBIaN3yw= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=w5UMrwUa; spf=pass (imf25.hostedemail.com: domain of roman.gushchin@linux.dev designates 95.215.58.171 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev; dmarc=pass (policy=none) header.from=linux.dev 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=1761607091; 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=1pBvFLnmQUGhHDldbyfAqGwleevT81Px3hvXcQya18A=; b=w5UMrwUaoMs+GXh5EBhwvblLHe56g5Uq//mZp5YrlIP4NiHqkzroAOo1KdY9GZFzBBdZBH tdNPolJqq+i4qqTGuetYltCar6ZHnLfsICgRE7BoeH/soUxhA0t7GyTI/CnWvYY8sjfHvL ewVRkWVHPz9s4vIAASuiU7JSKnftYcI= From: Roman Gushchin To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Alexei Starovoitov , Suren Baghdasaryan , Michal Hocko , Shakeel Butt , Johannes Weiner , Andrii Nakryiko , JP Kobryn , linux-mm@kvack.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Kumar Kartikeya Dwivedi , Tejun Heo , Roman Gushchin Subject: [PATCH v2 08/23] mm: introduce BPF kfuncs to deal with memcg pointers Date: Mon, 27 Oct 2025 16:17:11 -0700 Message-ID: <20251027231727.472628-9-roman.gushchin@linux.dev> In-Reply-To: <20251027231727.472628-1-roman.gushchin@linux.dev> References: <20251027231727.472628-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam05 X-Stat-Signature: mq4frgikg7qdjutpdsi71hf6uhjmzaq5 X-Rspam-User: X-Rspamd-Queue-Id: 0C097A0008 X-HE-Tag: 1761607092-390900 X-HE-Meta: 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 z08WcxER SfIaskJrXjwZjdg/do2Tti2NkT2FDYzoMkdF02rNsp2mLd8+VXeg9vOwSEhm5pPxM8b/csiMbncj3x4qagJp5c/qgfMP+ytYg21xBV+dNW2dxAQsqSNxppyR95ZcABqQrJ2fra+hqSfN51GcDaAcmNvmgNeuDiR/HKWe7poAoiHlx1nFBCdiEaI/0KUDKiSanteeuUnh31Ep0gycQB1cgAAFPgzawZQLCtCucB8vzEBBLNDU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: To effectively operate with memory cgroups in BPF there is a need to convert css pointers to memcg pointers. A simple container_of cast which is used in the kernel code can't be used in BPF because from the verifier's point of view that's a out-of-bounds memory access. Introduce helper get/put kfuncs which can be used to get a refcounted memcg pointer from the css pointer: - bpf_get_mem_cgroup, - bpf_put_mem_cgroup. bpf_get_mem_cgroup() can take both memcg's css and the corresponding cgroup's "self" css. It allows it to be used with the existing cgroup iterator which iterates over cgroup tree, not memcg tree. Signed-off-by: Roman Gushchin --- mm/Makefile | 1 + mm/bpf_memcontrol.c | 88 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 89 insertions(+) create mode 100644 mm/bpf_memcontrol.c diff --git a/mm/Makefile b/mm/Makefile index 051e88c699af..2d8f9beb3c71 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -107,6 +107,7 @@ obj-$(CONFIG_MEMCG) += swap_cgroup.o endif ifdef CONFIG_BPF_SYSCALL obj-y += bpf_oom.o +obj-$(CONFIG_MEMCG) += bpf_memcontrol.o endif obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o obj-$(CONFIG_GUP_TEST) += gup_test.o diff --git a/mm/bpf_memcontrol.c b/mm/bpf_memcontrol.c new file mode 100644 index 000000000000..1e46097745cf --- /dev/null +++ b/mm/bpf_memcontrol.c @@ -0,0 +1,88 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Memory Controller-related BPF kfuncs and auxiliary code + * + * Author: Roman Gushchin + */ + +#include +#include + +__bpf_kfunc_start_defs(); + +/** + * bpf_get_mem_cgroup - Get a reference to a memory cgroup + * @css: pointer to the css structure + * + * Returns a pointer to a mem_cgroup structure after bumping + * the corresponding css's reference counter. + * + * It's fine to pass a css which belongs to any cgroup controller, + * e.g. unified hierarchy's main css. + * + * Implements KF_ACQUIRE semantics. + */ +__bpf_kfunc struct mem_cgroup * +bpf_get_mem_cgroup(struct cgroup_subsys_state *css) +{ + struct mem_cgroup *memcg = NULL; + bool rcu_unlock = false; + + if (!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_kfunc_end_defs(); + +BTF_KFUNCS_START(bpf_memcontrol_kfuncs) +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_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_STRUCT_OPS, + &bpf_memcontrol_kfunc_set); + if (err) + pr_warn("error while registering bpf memcontrol kfuncs: %d", err); + + return err; +} +late_initcall(bpf_memcontrol_init); -- 2.51.0