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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0B36CE7AEB for ; Thu, 28 Sep 2023 02:52:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230044AbjI1CwM (ORCPT ); Wed, 27 Sep 2023 22:52:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229437AbjI1CwL (ORCPT ); Wed, 27 Sep 2023 22:52:11 -0400 Received: from mail-pf1-x42c.google.com (mail-pf1-x42c.google.com [IPv6:2607:f8b0:4864:20::42c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A478694 for ; Wed, 27 Sep 2023 19:51:50 -0700 (PDT) Received: by mail-pf1-x42c.google.com with SMTP id d2e1a72fcca58-690bd59322dso9658221b3a.3 for ; Wed, 27 Sep 2023 19:51:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1695869510; x=1696474310; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:from:to:cc:subject:date :message-id:reply-to; bh=ZxowYtqCHs25qaqAMSozKR4qYyXzSppOa5N6Ri1v7lw=; b=V/AUFgeVnMxiWuev+g71ntnlhTFnh3fmdxhsURsp9MlliZH9b+mw5RlLrtNLwON2iv 66gIgOdN0dz8tROhDCmgTHnr2ZTfa5oeQehHAx04SgDDsw8DnYB4xTTxaWT3uToHS36H heApkcxDQeoLP1wXRjvKIF6hr9/x4PB4rT6AgP5f/vULA0ezpkXBmN4bzYVATSj5gyU9 3PX6rLhjLOFxu4g46ee3lCky+XqCB6gSOK4Tw3por5lwc18cEHIcGCKbRwr7BgUjvmcW BNS4WsrEeyidcvA05+mAKFw8/gt5M0UsFx8pj045r28z06LBLiihxwT5K+lYdB4m5IiG 6seA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695869510; x=1696474310; h=content-transfer-encoding:in-reply-to:from:references:cc:to:subject :user-agent:mime-version:date:message-id:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=ZxowYtqCHs25qaqAMSozKR4qYyXzSppOa5N6Ri1v7lw=; b=Nu2wxMlufrLAhhtx06aUvgAC3sB3sgL4Lu9ZxXyReBYgjNnZhVqbTQpJ4f7o623vyY /ZX3bSIJJT1pa/6lslg06bKUfabIPq3bJpEEnX+88e11xTuxDktyKCUj+dIEb2bIsyRw iEOxnfdmI+1lfIaNTgwhPcG/zr2Tc05TmPPixqqy7g+FA96ApYSctaz4a+cVr7IW7MA+ ut0gRfOAFT5roATgMpMZIlCICRJeXTM+0zk3seE3tIV9KCvqRD1wt6ln4IRLY2z54UtA Flp5ixZgOgx0GrxScb2nP/A0HQXcSX5fCSOu91WbgFMCM+0cxGRYT2kUAYenVkSttnvE Bupg== X-Gm-Message-State: AOJu0YzcYHG6jMZV+wxQ4KH60yKFNqeUucAZkjzAoJA5dNGDYcTDP7fY xAlkI9qrMrGIykzoECShrM8CdLPV5W9l/GnUIew= X-Google-Smtp-Source: AGHT+IGV6hbjpD+iwlxnv3egrK1x6PxftppEsP97nF7d/SVaEZe4d9dHDpT0zGQ0GKrkPxmq43gp3A== X-Received: by 2002:a05:6a20:3d0f:b0:135:110c:c6e1 with SMTP id y15-20020a056a203d0f00b00135110cc6e1mr9636pzi.7.1695869509996; Wed, 27 Sep 2023 19:51:49 -0700 (PDT) Received: from [10.255.173.165] ([139.177.225.224]) by smtp.gmail.com with ESMTPSA id 28-20020a17090a191c00b0026801e06ac1sm13818445pjg.30.2023.09.27.19.51.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Sep 2023 19:51:49 -0700 (PDT) Message-ID: <27b57638-48db-7082-2b53-93d84e423350@bytedance.com> Date: Thu, 28 Sep 2023 10:51:43 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH bpf-next v3 4/7] bpf: Introduce css open-coded iterator kfuncs To: Andrii Nakryiko Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org, tj@kernel.org, linux-kernel@vger.kernel.org References: <20230925105552.817513-1-zhouchuyi@bytedance.com> <20230925105552.817513-5-zhouchuyi@bytedance.com> From: Chuyi Zhou In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, 在 2023/9/28 07:24, Andrii Nakryiko 写道: > On Mon, Sep 25, 2023 at 3:56 AM Chuyi Zhou wrote: >> >> This Patch adds kfuncs bpf_iter_css_{new,next,destroy} which allow >> creation and manipulation of struct bpf_iter_css in open-coded iterator >> style. These kfuncs actually wrapps css_next_descendant_{pre, post}. >> css_iter can be used to: >> >> 1) iterating a sepcific cgroup tree with pre/post/up order >> >> 2) iterating cgroup_subsystem in BPF Prog, like >> for_each_mem_cgroup_tree/cpuset_for_each_descendant_pre in kernel. >> >> The API design is consistent with cgroup_iter. bpf_iter_css_new accepts >> parameters defining iteration order and starting css. Here we also reuse >> BPF_CGROUP_ITER_DESCENDANTS_PRE, BPF_CGROUP_ITER_DESCENDANTS_POST, >> BPF_CGROUP_ITER_ANCESTORS_UP enums. >> >> Signed-off-by: Chuyi Zhou >> --- >> kernel/bpf/cgroup_iter.c | 57 +++++++++++++++++++ >> kernel/bpf/helpers.c | 3 + >> .../testing/selftests/bpf/bpf_experimental.h | 6 ++ >> 3 files changed, 66 insertions(+) >> >> diff --git a/kernel/bpf/cgroup_iter.c b/kernel/bpf/cgroup_iter.c >> index 810378f04fbc..ebc3d9471f52 100644 >> --- a/kernel/bpf/cgroup_iter.c >> +++ b/kernel/bpf/cgroup_iter.c >> @@ -294,3 +294,60 @@ static int __init bpf_cgroup_iter_init(void) >> } >> >> late_initcall(bpf_cgroup_iter_init); >> + >> +struct bpf_iter_css { >> + __u64 __opaque[2]; >> + __u32 __opaque_int[1]; >> +} __attribute__((aligned(8))); >> + > > same as before, __opaque[3] only > > >> +struct bpf_iter_css_kern { >> + struct cgroup_subsys_state *start; >> + struct cgroup_subsys_state *pos; >> + int order; >> +} __attribute__((aligned(8))); >> + >> +__bpf_kfunc int bpf_iter_css_new(struct bpf_iter_css *it, >> + struct cgroup_subsys_state *start, enum bpf_cgroup_iter_order order) > > Similarly, I wonder if we should go for a more generic "flags" argument? > >> +{ >> + struct bpf_iter_css_kern *kit = (void *)it; > > empty line > >> + kit->start = NULL; >> + BUILD_BUG_ON(sizeof(struct bpf_iter_css_kern) != sizeof(struct bpf_iter_css)); >> + BUILD_BUG_ON(__alignof__(struct bpf_iter_css_kern) != __alignof__(struct bpf_iter_css)); > > please move this up before kit->start assignment, and separate by empty lines > >> + switch (order) { >> + case BPF_CGROUP_ITER_DESCENDANTS_PRE: >> + case BPF_CGROUP_ITER_DESCENDANTS_POST: >> + case BPF_CGROUP_ITER_ANCESTORS_UP: >> + break; >> + default: >> + return -EINVAL; >> + } >> + >> + kit->start = start; >> + kit->pos = NULL; >> + kit->order = order; >> + return 0; >> +} >> + >> +__bpf_kfunc struct cgroup_subsys_state *bpf_iter_css_next(struct bpf_iter_css *it) >> +{ >> + struct bpf_iter_css_kern *kit = (void *)it; > > empty line > >> + if (!kit->start) >> + return NULL; >> + >> + switch (kit->order) { >> + case BPF_CGROUP_ITER_DESCENDANTS_PRE: >> + kit->pos = css_next_descendant_pre(kit->pos, kit->start); >> + break; >> + case BPF_CGROUP_ITER_DESCENDANTS_POST: >> + kit->pos = css_next_descendant_post(kit->pos, kit->start); >> + break; >> + default: > > we know it's BPF_CGROUP_ITER_ANCESTORS_UP, so why not have that here explicitly? > >> + kit->pos = kit->pos ? kit->pos->parent : kit->start; >> + } >> + >> + return kit->pos; > > wouldn't this implementation never return the "start" css? is that intentional? > Thanks for the review. This implementation actually would return the "start" css. 1. BPF_CGROUP_ITER_DESCENDANTS_PRE: 1.1 when we first call next(), css_next_descendant_pre(NULL, kit->start) will return kit->start. 1.2 second call next(), css_next_descendant_pre(kit->start, kit->start) would return a first valid child under kit->start with pre-order 1.3 third call next, css_next_descendant_pre(last_valid_child, kit->start) would return the next valid child ... util css_next_descendant_pre return a NULL pointer, which means we have visited all valid child including "start" css itself. The above logic is equal to macro 'css_for_each_descendant_pre' in kernel. Same, BPF_CGROUP_ITER_DESCENDANTS_POST is equal to macro 'css_for_each_descendant_post' which would return 'start' css when we have visited all valid child. 2. BPF_CGROUP_ITER_ANCESTORS_UP 2.1 when we fisrt call next(), kit->pos is NULL, and we would return kit->start. The selftest in patch7 whould check: 1. when we use BPF_CGROUP_ITER_DESCENDANTS_PRE to iterate a cgroup tree, the first cgroup we visted should be root('start') cgroup. 2. when we use BPF_CGROUP_ITER_DESCENDANTS_POST to iterate a cgroup tree, the last cgroup we visited should be root('start') cgroup. Am I miss something important? Thanks.