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 E80D1C433EF for ; Thu, 3 Mar 2022 03:03:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231935AbiCCDEm (ORCPT ); Wed, 2 Mar 2022 22:04:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48100 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231912AbiCCDEi (ORCPT ); Wed, 2 Mar 2022 22:04:38 -0500 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2DCDED96C; Wed, 2 Mar 2022 19:03:53 -0800 (PST) Received: by mail-pg1-x544.google.com with SMTP id 12so3376907pgd.0; Wed, 02 Mar 2022 19:03:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=1T2pQiZbXMlGRmXFIqTrOqvgWauP+ciwm+r1geHJ1uw=; b=cw+fwGH+AFgfI573z/Ws8CS0mauU3imZKGGexYFtW6cSLkZYt0SkWENuPuy+pCMCq7 1EZVnDReKyHSZj9UGj2VL+sDQJm6VS/7fCYcSWVsjCiIS+ketVqBJWlAzk9yBCJn4xox pG0SD1pkfgEVZF4UOMfJ8gKBJfAuqZRfbUR9RWnLHQiTId28XLioZIHDKuYacJSMV66k hh2Flbv18XxBuDvIx2s91Ijo1Gnw9eLGE/wp97+slWQb/YwgM1/SFDeRTvCpGmR3tVM5 ybmQma7l7D5r5Lvo6bwU/YELWXMoWGyPgefrcWZHEckrniVLnmDDsMgJf1WGwRrtoAvi z+dA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=1T2pQiZbXMlGRmXFIqTrOqvgWauP+ciwm+r1geHJ1uw=; b=1wrlRWGM/i1Nk2++X6F8M3DMm0L8DR9zTQTJGFB0gyCkWyNrIIbNCG8I9OKPZczzdZ bD/Y2nemkqjaahCwakVIpuhCKQGXo4O51bLYEFVOP9QnQdLogstLekyJjCPjEXCevKI3 AQdYywAPBa13im9TDKQWIiE5cQXXcqhTZgU3VV+wnVAfBg/vx2aY3mjTPXmJZh3pOi/J DnQRFK0S/63gaYLV4ljiInsNR8CRvacoalV4x4GtlTRZhPRzUc+I5hF5HFbSZSzfNr08 LSyd/72ygqu6PeQgomAYwjWymFIlXb7uyq80+06ouZffMWzRC+NL7mL9QO6ZcZt8YQap l6cw== X-Gm-Message-State: AOAM5320f+yTPVS9aPg+crm/R44Y1ZjTQ1GF3BhqOQoN3r7121JxEWA2 8/CijGjjHr6MWWC4PAOrOcg= X-Google-Smtp-Source: ABdhPJz5Mddl9rcZtv4HDTnH0mTxyJ7dFwmBYJCQvR3sS9HN8w9/82ndp6bB7WqGsFMmXqSm779Y4w== X-Received: by 2002:a63:1c15:0:b0:372:ffcd:4d21 with SMTP id c21-20020a631c15000000b00372ffcd4d21mr28631649pgc.450.1646276633238; Wed, 02 Mar 2022 19:03:53 -0800 (PST) Received: from localhost ([2405:201:6014:d0c0:6243:316e:a9e1:adda]) by smtp.gmail.com with ESMTPSA id bh3-20020a056a02020300b00378b62df320sm470171pgb.73.2022.03.02.19.03.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Mar 2022 19:03:52 -0800 (PST) Date: Thu, 3 Mar 2022 08:33:49 +0530 From: Kumar Kartikeya Dwivedi To: Yonghong Song Cc: Hao Luo , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Song Liu , KP Singh , Shakeel Butt , Joe Burton , Tejun Heo , joshdon@google.com, sdf@google.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next v1 8/9] bpf: Introduce cgroup iter Message-ID: <20220303030349.drd7mmwtufl45p3u@apollo.legion> References: <20220225234339.2386398-1-haoluo@google.com> <20220225234339.2386398-9-haoluo@google.com> <20220302224506.jc7jwkdaatukicik@apollo.legion> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 03, 2022 at 07:33:16AM IST, Yonghong Song wrote: > > > On 3/2/22 2:45 PM, Kumar Kartikeya Dwivedi wrote: > > On Sat, Feb 26, 2022 at 05:13:38AM IST, Hao Luo wrote: > > > Introduce a new type of iter prog: cgroup. Unlike other bpf_iter, this > > > iter doesn't iterate a set of kernel objects. Instead, it is supposed to > > > be parameterized by a cgroup id and prints only that cgroup. So one > > > needs to specify a target cgroup id when attaching this iter. > > > > > > The target cgroup's state can be read out via a link of this iter. > > > Typically, we can monitor cgroup creation and deletion using sleepable > > > tracing and use it to create corresponding directories in bpffs and pin > > > a cgroup id parameterized link in the directory. Then we can read the > > > auto-pinned iter link to get cgroup's state. The output of the iter link > > > is determined by the program. See the selftest test_cgroup_stats.c for > > > an example. > > > > > > Signed-off-by: Hao Luo > > > --- > > > include/linux/bpf.h | 1 + > > > include/uapi/linux/bpf.h | 6 ++ > > > kernel/bpf/Makefile | 2 +- > > > kernel/bpf/cgroup_iter.c | 141 +++++++++++++++++++++++++++++++++ > > > tools/include/uapi/linux/bpf.h | 6 ++ > > > 5 files changed, 155 insertions(+), 1 deletion(-) > > > create mode 100644 kernel/bpf/cgroup_iter.c > > > > > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > > > index 759ade7b24b3..3ce9b0b7ed89 100644 > > > --- a/include/linux/bpf.h > > > +++ b/include/linux/bpf.h > > > @@ -1595,6 +1595,7 @@ int bpf_obj_get_path(bpfptr_t pathname, int flags); > > > > > > struct bpf_iter_aux_info { > > > struct bpf_map *map; > > > + u64 cgroup_id; > > > }; > > > > > > typedef int (*bpf_iter_attach_target_t)(struct bpf_prog *prog, > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > > > index a5dbc794403d..855ad80d9983 100644 > > > --- a/include/uapi/linux/bpf.h > > > +++ b/include/uapi/linux/bpf.h > > > @@ -91,6 +91,9 @@ union bpf_iter_link_info { > > > struct { > > > __u32 map_fd; > > > } map; > > > + struct { > > > + __u64 cgroup_id; > > > + } cgroup; > > > }; > > > > > > /* BPF syscall commands, see bpf(2) man-page for more details. */ > > > @@ -5887,6 +5890,9 @@ struct bpf_link_info { > > > struct { > > > __u32 map_id; > > > } map; > > > + struct { > > > + __u64 cgroup_id; > > > + } cgroup; > > > }; > > > } iter; > > > struct { > > > diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile > > > index c1a9be6a4b9f..52a0e4c6e96e 100644 > > > --- a/kernel/bpf/Makefile > > > +++ b/kernel/bpf/Makefile > > > @@ -8,7 +8,7 @@ CFLAGS_core.o += $(call cc-disable-warning, override-init) $(cflags-nogcse-yy) > > > > > > obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o prog_iter.o > > > obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o bloom_filter.o > > > -obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o > > > +obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o cgroup_iter.o > > > obj-$(CONFIG_BPF_SYSCALL) += bpf_local_storage.o bpf_task_storage.o > > > obj-${CONFIG_BPF_LSM} += bpf_inode_storage.o > > > obj-$(CONFIG_BPF_SYSCALL) += disasm.o > > > diff --git a/kernel/bpf/cgroup_iter.c b/kernel/bpf/cgroup_iter.c > > > new file mode 100644 > > > index 000000000000..011d9dcd1d51 > > > --- /dev/null > > > +++ b/kernel/bpf/cgroup_iter.c > > > @@ -0,0 +1,141 @@ > > > +// SPDX-License-Identifier: GPL-2.0-only > > > +/* Copyright (c) 2022 Google */ > > > +#include > > > +#include > > > +#include > > > +#include > > > +#include > > > + > > > +struct bpf_iter__cgroup { > > > + __bpf_md_ptr(struct bpf_iter_meta *, meta); > > > + __bpf_md_ptr(struct cgroup *, cgroup); > > > +}; > > > + > > > +static void *cgroup_iter_seq_start(struct seq_file *seq, loff_t *pos) > > > +{ > > > + struct cgroup *cgroup; > > > + u64 cgroup_id; > > > + > > > + /* Only one session is supported. */ > > > + if (*pos > 0) > > > + return NULL; > > > + > > > + cgroup_id = *(u64 *)seq->private; > > > + cgroup = cgroup_get_from_id(cgroup_id); > > > + if (!cgroup) > > > + return NULL; > > > + > > > + if (*pos == 0) > > > + ++*pos; > > > + > > > + return cgroup; > > > +} > > > + > > > +static void *cgroup_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos) > > > +{ > > > + ++*pos; > > > + return NULL; > > > +} > > > + > > > +static int cgroup_iter_seq_show(struct seq_file *seq, void *v) > > > +{ > > > + struct bpf_iter__cgroup ctx; > > > + struct bpf_iter_meta meta; > > > + struct bpf_prog *prog; > > > + int ret = 0; > > > + > > > + ctx.meta = &meta; > > > + ctx.cgroup = v; > > > + meta.seq = seq; > > > + prog = bpf_iter_get_info(&meta, false); > > > + if (prog) > > > + ret = bpf_iter_run_prog(prog, &ctx); > > > + > > > + return ret; > > > +} > > > + > > > +static void cgroup_iter_seq_stop(struct seq_file *seq, void *v) > > > +{ > > > + if (v) > > > + cgroup_put(v); > > > +} > > > > I think in existing iterators, we make a final call to seq_show, with v as NULL, > > is there a specific reason to do it differently for this? There is logic in > > bpf_iter.c to trigger ->stop() callback again when ->start() or ->next() returns > > NULL, to execute BPF program with NULL p, see the comment above stop label. > > > > If you do add the seq_show call with NULL, you'd also need to change the > > ctx_arg_info PTR_TO_BTF_ID to PTR_TO_BTF_ID_OR_NULL. > > Kumar, PTR_TO_BTF_ID should be okay since the show() never takes a non-NULL > cgroup. But we do have issues for cgroup_iter_seq_stop() which I missed > earlier. > Right, I was thinking whether it should call seq_show for v == NULL case. All other iterators seem to do so, it's a bit different here since it is only iterating over a single cgroup, I guess, but it would be nice to have some consistency. > For cgroup_iter, the following is the current workflow: > start -> not NULL -> show -> next -> NULL -> stop > or > start -> NULL -> stop > > So for cgroup_iter_seq_stop, the input parameter 'v' will be NULL, so > the cgroup_put() is not actually called, i.e., corresponding cgroup is > not freed. > > There are two ways to fix the issue: > . call cgroup_put() in next() before return NULL. This way, > stop() will be a noop. > . put cgroup_get_from_id() and cgroup_put() in > bpf_iter_attach_cgroup() and bpf_iter_detach_cgroup(). > > I prefer the second approach as it is cleaner. > I think current approach is also not safe if cgroup_id gets reused, right? I.e. it only does cgroup_get_from_id in seq_start, not at attach time, so it may not be the same cgroup when calling read(2). kernfs is using idr_alloc_cyclic, so it is less likely to occur, but since it wraps around to find a free ID it might not be theoretical. > > > > > + > > > +static const struct seq_operations cgroup_iter_seq_ops = { > > > + .start = cgroup_iter_seq_start, > > > + .next = cgroup_iter_seq_next, > > > + .stop = cgroup_iter_seq_stop, > > > + .show = cgroup_iter_seq_show, > > > +}; > > > + > > > +BTF_ID_LIST_SINGLE(bpf_cgroup_btf_id, struct, cgroup) > > > + > > > +static int cgroup_iter_seq_init(void *priv_data, struct bpf_iter_aux_info *aux) > > > +{ > > > + *(u64 *)priv_data = aux->cgroup_id; > > > + return 0; > > > +} > > > + > > > +static void cgroup_iter_seq_fini(void *priv_data) > > > +{ > > > +} > > > + > > > +static const struct bpf_iter_seq_info cgroup_iter_seq_info = { > > > + .seq_ops = &cgroup_iter_seq_ops, > > > + .init_seq_private = cgroup_iter_seq_init, > > > + .fini_seq_private = cgroup_iter_seq_fini, > > > + .seq_priv_size = sizeof(u64), > > > +}; > > > + > > > +static int bpf_iter_attach_cgroup(struct bpf_prog *prog, > > > + union bpf_iter_link_info *linfo, > > > + struct bpf_iter_aux_info *aux) > > > +{ > > > + aux->cgroup_id = linfo->cgroup.cgroup_id; > > > + return 0; > > > +} > > > + > > > +static void bpf_iter_detach_cgroup(struct bpf_iter_aux_info *aux) > > > +{ > > > +} > > > + > > > +void bpf_iter_cgroup_show_fdinfo(const struct bpf_iter_aux_info *aux, > > > + struct seq_file *seq) > > > +{ > > > + char buf[64] = {0}; > > > + > > > + cgroup_path_from_kernfs_id(aux->cgroup_id, buf, sizeof(buf)); > > > + seq_printf(seq, "cgroup_id:\t%lu\n", aux->cgroup_id); > > > + seq_printf(seq, "cgroup_path:\t%s\n", buf); > > > +} > > > + > > > +int bpf_iter_cgroup_fill_link_info(const struct bpf_iter_aux_info *aux, > > > + struct bpf_link_info *info) > > > +{ > > > + info->iter.cgroup.cgroup_id = aux->cgroup_id; > > > + return 0; > > > +} > > > + > > > +DEFINE_BPF_ITER_FUNC(cgroup, struct bpf_iter_meta *meta, > > > + struct cgroup *cgroup) > > > + > > > +static struct bpf_iter_reg bpf_cgroup_reg_info = { > > > + .target = "cgroup", > > > + .attach_target = bpf_iter_attach_cgroup, > > > + .detach_target = bpf_iter_detach_cgroup, > > > + .show_fdinfo = bpf_iter_cgroup_show_fdinfo, > > > + .fill_link_info = bpf_iter_cgroup_fill_link_info, > > > + .ctx_arg_info_size = 1, > > > + .ctx_arg_info = { > > > + { offsetof(struct bpf_iter__cgroup, cgroup), > > > + PTR_TO_BTF_ID }, > > > + }, > > > + .seq_info = &cgroup_iter_seq_info, > > > +}; > > > + > > > +static int __init bpf_cgroup_iter_init(void) > > > +{ > > > + bpf_cgroup_reg_info.ctx_arg_info[0].btf_id = bpf_cgroup_btf_id[0]; > > > + return bpf_iter_reg_target(&bpf_cgroup_reg_info); > > > +} > > > + > > > +late_initcall(bpf_cgroup_iter_init); > > > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h > > > index a5dbc794403d..855ad80d9983 100644 > > > --- a/tools/include/uapi/linux/bpf.h > > > +++ b/tools/include/uapi/linux/bpf.h > > > @@ -91,6 +91,9 @@ union bpf_iter_link_info { > > > struct { > > > __u32 map_fd; > > > } map; > > > + struct { > > > + __u64 cgroup_id; > > > + } cgroup; > > > }; > > > > > > /* BPF syscall commands, see bpf(2) man-page for more details. */ > > > @@ -5887,6 +5890,9 @@ struct bpf_link_info { > > > struct { > > > __u32 map_id; > > > } map; > > > + struct { > > > + __u64 cgroup_id; > > > + } cgroup; > > > }; > > > } iter; > > > struct { > > > -- > > > 2.35.1.574.g5d30c73bfb-goog > > > > > > > -- > > Kartikeya -- Kartikeya