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 X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66E61C4743C for ; Fri, 4 Jun 2021 17:54:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4FFE6611F0 for ; Fri, 4 Jun 2021 17:54:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230322AbhFDR4T (ORCPT ); Fri, 4 Jun 2021 13:56:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36576 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229690AbhFDR4T (ORCPT ); Fri, 4 Jun 2021 13:56:19 -0400 Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E603FC061767; Fri, 4 Jun 2021 10:54:32 -0700 (PDT) Received: by mail-pj1-x1029.google.com with SMTP id l23-20020a17090a0717b029016ae774f973so5669939pjl.1; Fri, 04 Jun 2021 10:54:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=01y5NneuXQw40lmFbAzFmDqnYxSeLx36MZRmrGk1JLI=; b=cxt2Dks5H/GR9EVFvdhJx2a6Ft/DwAb6bkMdUXu4qPaZUKOi/9+PSwG6VmT1JLP9gS PWplWjjX7gkOJLoCXdpVZ3GzKp3RpWKksDodwJTH//7rnqwXC+M3md6jXof46Ad1KPN0 lljPi/lN3UpmdaCvRkQsu9YgvOaH+fAmWU/NhfnQRgFH8LK73y1I5etjGZAG6tPt/wmY jdG23fL+t9S5dFmHY3b578L3wS+cxN4FkF4KmEFEnIZWsOjyQwFJvGOQHXCLdRJk1yJE ZeGhJHONGmhNhqLRKDwH5Rgo7U2Oi+9CaQRyk2ob+D5srCA+P2ZJ3f5KQGoq2zGWQCa7 zu4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=01y5NneuXQw40lmFbAzFmDqnYxSeLx36MZRmrGk1JLI=; b=j8rQf150a2MJeT09MvmQKe+1mLhDY2J1nWVeyDqSniTs9iZHet1o37lg2s1LQyyEkB J51jta+BZp8f/rvNtx5BwxCshKPafFviptzeXsslVjLC6Y8cFKe3OMBHAdFmHUTO8g6f 8oVtaiawxv3PVhY7frkid5bw4C5zQZaP4GUEZZjJ7COqaFe0KLaUn4k8T78hL0SawNxx 4cy/z+2th7GHQuu0bB4EXuydkTUeJEfRUgpFyljmOyDTW3GW+yWgtf3aNZZeOadZs2AM 2zjmeocPWIPCeuEXKBspVuCNPM5nSoukCBKP3D2wpuRqliR4TBhbJQJ0YiUUquv31+VI L+jg== X-Gm-Message-State: AOAM532SpUYwvEHYn1Qht37Dd/p0MayTSX+/TJrMeFV4G6AzQ3PhsQO/ Oq6rXH83VtAFHQ2OLcFlnT0U7s/gzSI= X-Google-Smtp-Source: ABdhPJwaPCpcYRfMqrFvQQcEcoDHBujHWQs1Tk96C6pX5anR3fM3wbWGCz9yWfnzfRptw0yW8HxeKQ== X-Received: by 2002:a17:902:b58a:b029:fe:735f:ddbf with SMTP id a10-20020a170902b58ab02900fe735fddbfmr5319876pls.68.1622829272301; Fri, 04 Jun 2021 10:54:32 -0700 (PDT) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:400::5:862d]) by smtp.gmail.com with ESMTPSA id u7sm2691656pgl.39.2021.06.04.10.54.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Jun 2021 10:54:31 -0700 (PDT) Date: Fri, 4 Jun 2021 10:54:28 -0700 From: Alexei Starovoitov To: Kumar Kartikeya Dwivedi Cc: bpf@vger.kernel.org, Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Jamal Hadi Salim , Vlad Buslov , Cong Wang , Jesper Dangaard Brouer , netdev@vger.kernel.org Subject: Re: [PATCH bpf-next v2 4/7] net: sched: add lightweight update path for cls_bpf Message-ID: <20210604175428.f77zeagqavjvdndn@ast-mbp.dhcp.thefacebook.com> References: <20210604063116.234316-1-memxor@gmail.com> <20210604063116.234316-5-memxor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210604063116.234316-5-memxor@gmail.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jun 04, 2021 at 12:01:13PM +0530, Kumar Kartikeya Dwivedi wrote: > This is used by BPF_LINK_UPDATE to replace the attach SCHED_CLS bpf prog > effectively changing the classifier implementation for a given filter > owned by a bpf_link. > > Note that READ_ONCE suffices in this case as the ordering for loads from > the filter are implicitly provided by the data dependency on BPF prog > pointer. > > On the writer side we can just use a relaxed WRITE_ONCE store to make > sure one or the other value is visible to a reader in cls_bpf_classify. > Lifetime is managed using RCU so bpf_prog_put path should wait until > readers are done for old_prog. Should those be rcu_deref and rcu_assign_pointer ? Typically the pointer would be __rcu annotated which would be another small change in struct cls_bpf_prog. That would make the life time easier to follow? > All other parties accessing the BPF prog are under RTNL protection, so > need no changes. > > Reviewed-by: Toke Høiland-Jørgensen . > Signed-off-by: Kumar Kartikeya Dwivedi > --- > net/sched/cls_bpf.c | 55 +++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 53 insertions(+), 2 deletions(-) > > diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c > index bf61ffbb7fd0..f23304685c48 100644 > --- a/net/sched/cls_bpf.c > +++ b/net/sched/cls_bpf.c > @@ -9,6 +9,7 @@ > * (C) 2013 Daniel Borkmann > */ > > +#include > #include > #include > #include > @@ -104,11 +105,11 @@ static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp, > /* It is safe to push/pull even if skb_shared() */ > __skb_push(skb, skb->mac_len); > bpf_compute_data_pointers(skb); > - filter_res = BPF_PROG_RUN(prog->filter, skb); > + filter_res = BPF_PROG_RUN(READ_ONCE(prog->filter), skb); > __skb_pull(skb, skb->mac_len); > } else { > bpf_compute_data_pointers(skb); > - filter_res = BPF_PROG_RUN(prog->filter, skb); > + filter_res = BPF_PROG_RUN(READ_ONCE(prog->filter), skb); > } > > if (prog->exts_integrated) { > @@ -775,6 +776,55 @@ static int cls_bpf_link_detach(struct bpf_link *link) > return 0; > } > > +static int cls_bpf_link_update(struct bpf_link *link, struct bpf_prog *new_prog, > + struct bpf_prog *old_prog) > +{ > + struct cls_bpf_link *cls_link; > + struct cls_bpf_prog cls_prog; > + struct cls_bpf_prog *prog; > + int ret; > + > + rtnl_lock(); > + > + cls_link = container_of(link, struct cls_bpf_link, link); > + if (!cls_link->prog) { > + ret = -ENOLINK; > + goto out; > + } > + > + prog = cls_link->prog; > + > + /* BPF_F_REPLACEing? */ > + if (old_prog && prog->filter != old_prog) { > + ret = -EINVAL; Other places like cgroup_bpf_replace and bpf_iter_link_replace return -EPERM in such case. > + goto out; > + } > + > + old_prog = prog->filter; > + > + if (new_prog == old_prog) { > + ret = 0; > + goto out; > + } > + > + cls_prog = *prog; > + cls_prog.filter = new_prog; > + > + ret = cls_bpf_offload(prog->tp, &cls_prog, prog, NULL); > + if (ret < 0) > + goto out; > + > + WRITE_ONCE(prog->filter, new_prog); > + > + bpf_prog_inc(new_prog); > + /* release our reference */ > + bpf_prog_put(old_prog); > + > +out: > + rtnl_unlock(); > + return ret; > +} > + > static void __bpf_fill_link_info(struct cls_bpf_link *link, > struct bpf_link_info *info) > { > @@ -859,6 +909,7 @@ static const struct bpf_link_ops cls_bpf_link_ops = { > .show_fdinfo = cls_bpf_link_show_fdinfo, > #endif > .fill_link_info = cls_bpf_link_fill_link_info, > + .update_prog = cls_bpf_link_update, > }; > > static inline char *cls_bpf_link_name(u32 prog_id, const char *name) > -- > 2.31.1 > --