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 9D2CDC7618E for ; Mon, 24 Apr 2023 05:46:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229625AbjDXFqy (ORCPT ); Mon, 24 Apr 2023 01:46:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46668 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229478AbjDXFqx (ORCPT ); Mon, 24 Apr 2023 01:46:53 -0400 Received: from out-32.mta0.migadu.com (out-32.mta0.migadu.com [91.218.175.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF4BD92 for ; Sun, 23 Apr 2023 22:46:48 -0700 (PDT) Message-ID: <251b0a3f-47d6-d9ad-0c8e-b707fa286c7c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1682315206; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vDmcv6uyGAnhDJx5mX9MEy483v7hU9sc4J6YESMrcyE=; b=HomTK5dtFCTn38BqIUHZzseILB3HVhOvqt+t/yL6LkvLLRSHXEI++Sfw8MXID2oIdeaLRt o5MO3/a2K38pL6Vz7DBasYSd+VK6pOr9lL/dva+bStQRcH0++9Al1JhGO5FzXwRFxxv+S9 Tgw1y3Pk0aJQot3n8vPbFflVC745I3I= Date: Sun, 23 Apr 2023 22:46:38 -0700 MIME-Version: 1.0 Subject: Re: [PATCH 4/7] bpf: udp: Implement batching for sockets iterator Content-Language: en-US To: Aditi Ghag Cc: kafai@fb.com, sdf@google.com, edumazet@google.com, Martin KaFai Lau , bpf@vger.kernel.org References: <20230418153148.2231644-1-aditi.ghag@isovalent.com> <20230418153148.2231644-5-aditi.ghag@isovalent.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: <20230418153148.2231644-5-aditi.ghag@isovalent.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 4/18/23 8:31 AM, Aditi Ghag wrote: > Batch UDP sockets from BPF iterator that allows for overlapping locking > semantics in BPF/kernel helpers executed in BPF programs. This facilitates > BPF socket destroy kfunc (introduced by follow-up patches) to execute from > BPF iterator programs. > > Previously, BPF iterators acquired the sock lock and sockets hash table > bucket lock while executing BPF programs. This prevented BPF helpers that > again acquire these locks to be executed from BPF iterators. With the > batching approach, we acquire a bucket lock, batch all the bucket sockets, > and then release the bucket lock. This enables BPF or kernel helpers to > skip sock locking when invoked in the supported BPF contexts. > > The batching logic is similar to the logic implemented in TCP iterator: > https://lore.kernel.org/bpf/20210701200613.1036157-1-kafai@fb.com/. > > Suggested-by: Martin KaFai Lau > Signed-off-by: Aditi Ghag > --- > net/ipv4/udp.c | 209 +++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 203 insertions(+), 6 deletions(-) > > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c > index 8689ed171776..f1c001641e53 100644 > --- a/net/ipv4/udp.c > +++ b/net/ipv4/udp.c > @@ -3148,6 +3148,145 @@ struct bpf_iter__udp { > int bucket __aligned(8); > }; > > +struct bpf_udp_iter_state { > + struct udp_iter_state state; > + unsigned int cur_sk; > + unsigned int end_sk; > + unsigned int max_sk; > + int offset; > + struct sock **batch; > + bool st_bucket_done; > +}; > + > +static int bpf_iter_udp_realloc_batch(struct bpf_udp_iter_state *iter, > + unsigned int new_batch_sz); > +static struct sock *bpf_iter_udp_batch(struct seq_file *seq) > +{ > + struct bpf_udp_iter_state *iter = seq->private; > + struct udp_iter_state *state = &iter->state; > + struct net *net = seq_file_net(seq); > + struct udp_seq_afinfo afinfo; > + struct udp_table *udptable; > + unsigned int batch_sks = 0; > + bool resized = false; > + struct sock *sk; > + > + /* The current batch is done, so advance the bucket. */ > + if (iter->st_bucket_done) { > + state->bucket++; > + iter->offset = 0; > + } > + > + afinfo.family = AF_UNSPEC; > + afinfo.udp_table = NULL; > + udptable = udp_get_table_afinfo(&afinfo, net); > + > +again: > + /* New batch for the next bucket. > + * Iterate over the hash table to find a bucket with sockets matching > + * the iterator attributes, and return the first matching socket from > + * the bucket. The remaining matched sockets from the bucket are batched > + * before releasing the bucket lock. This allows BPF programs that are > + * called in seq_show to acquire the bucket lock if needed. > + */ > + iter->cur_sk = 0; > + iter->end_sk = 0; > + iter->st_bucket_done = false; > + batch_sks = 0; > + > + for (; state->bucket <= udptable->mask; state->bucket++) { > + struct udp_hslot *hslot2 = &udptable->hash2[state->bucket]; > + > + if (hlist_empty(&hslot2->head)) { > + iter->offset = 0; > + continue; > + } > + > + spin_lock_bh(&hslot2->lock); > + udp_portaddr_for_each_entry(sk, &hslot2->head) { > + if (seq_sk_match(seq, sk)) { > + /* Resume from the last iterated socket at the > + * offset in the bucket before iterator was stopped. > + */ > + if (iter->offset) { > + --iter->offset; > + continue; > + } > + if (iter->end_sk < iter->max_sk) { > + sock_hold(sk); > + iter->batch[iter->end_sk++] = sk; > + } > + batch_sks++; > + } > + } > + spin_unlock_bh(&hslot2->lock); > + > + if (iter->end_sk) > + break; > + > + /* Reset the current bucket's offset before moving to the next bucket. */ > + iter->offset = 0; > + } > + > + /* All done: no batch made. */ > + if (!iter->end_sk) > + return NULL; > + > + if (iter->end_sk == batch_sks) { > + /* Batching is done for the current bucket; return the first > + * socket to be iterated from the batch. > + */ > + iter->st_bucket_done = true; > + goto ret; nit. "ret" is a variable name in some other changes in this patch. How about directly "return iter->batch[0];" here or change the label name to something else like "done"? > + } > + if (!resized && !bpf_iter_udp_realloc_batch(iter, batch_sks * 3 / 2)) { > + resized = true; > + /* Go back to the previous bucket to resize its batch. */ nit. I found the "to resize its batch" part confusing. The resize has already been done in the above bpf_iter_udp_realloc_batch(). How about something like, "After getting a larger max_sk, retry one more time to grab the whole bucket" ? > + state->bucket--; > + goto again; > + } > +ret: > + return iter->batch[0]; > +} > + > +static void *bpf_iter_udp_seq_next(struct seq_file *seq, void *v, loff_t *pos) > +{ > + struct bpf_udp_iter_state *iter = seq->private; > + struct sock *sk; > + > + /* Whenever seq_next() is called, the iter->cur_sk is > + * done with seq_show(), so unref the iter->cur_sk. > + */ > + if (iter->cur_sk < iter->end_sk) { > + sock_put(iter->batch[iter->cur_sk++]); > + ++iter->offset; > + } > + > + /* After updating iter->cur_sk, check if there are more sockets > + * available in the current bucket batch. > + */ > + if (iter->cur_sk < iter->end_sk) { > + sk = iter->batch[iter->cur_sk]; > + } else { > + // Prepare a new batch. > + sk = bpf_iter_udp_batch(seq); > + } nit. remove "{ }" for one liner if-else statement. > + > + ++*pos; > + return sk; > +} > + > +static void *bpf_iter_udp_seq_start(struct seq_file *seq, loff_t *pos) > +{ > + /* bpf iter does not support lseek, so it always > + * continue from where it was stop()-ped. > + */ > + if (*pos) > + return bpf_iter_udp_batch(seq); > + > + return SEQ_START_TOKEN; > +} > + > static int udp_prog_seq_show(struct bpf_prog *prog, struct bpf_iter_meta *meta, > struct udp_sock *udp_sk, uid_t uid, int bucket) > { > @@ -3168,18 +3307,37 @@ static int bpf_iter_udp_seq_show(struct seq_file *seq, void *v) > struct bpf_prog *prog; > struct sock *sk = v; > uid_t uid; > + int rc; nit. be consistent with variable name. "ret" is used in other changes in this patch. > > if (v == SEQ_START_TOKEN) > return 0; > > + lock_sock(sk); > + > + if (unlikely(sk_unhashed(sk))) { > + rc = SEQ_SKIP; > + goto unlock; > + } > + > uid = from_kuid_munged(seq_user_ns(seq), sock_i_uid(sk)); > meta.seq = seq; > prog = bpf_iter_get_info(&meta, false); > - return udp_prog_seq_show(prog, &meta, v, uid, state->bucket); > + rc = udp_prog_seq_show(prog, &meta, v, uid, state->bucket); > + > +unlock: > + release_sock(sk); > + return rc; > +} > + > +static void bpf_iter_udp_put_batch(struct bpf_udp_iter_state *iter) > +{ > + while (iter->cur_sk < iter->end_sk) > + sock_put(iter->batch[iter->cur_sk++]); > } > > static void bpf_iter_udp_seq_stop(struct seq_file *seq, void *v) > { > + struct bpf_udp_iter_state *iter = seq->private; > struct bpf_iter_meta meta; > struct bpf_prog *prog; > > @@ -3190,12 +3348,15 @@ static void bpf_iter_udp_seq_stop(struct seq_file *seq, void *v) > (void)udp_prog_seq_show(prog, &meta, v, 0, 0); > } > > - udp_seq_stop(seq, v); > + if (iter->cur_sk < iter->end_sk) { > + bpf_iter_udp_put_batch(iter); > + iter->st_bucket_done = false; > + } > } > > static const struct seq_operations bpf_iter_udp_seq_ops = { > - .start = udp_seq_start, > - .next = udp_seq_next, > + .start = bpf_iter_udp_seq_start, > + .next = bpf_iter_udp_seq_next, > .stop = bpf_iter_udp_seq_stop, > .show = bpf_iter_udp_seq_show, > }; > @@ -3424,21 +3585,57 @@ static struct pernet_operations __net_initdata udp_sysctl_ops = { > DEFINE_BPF_ITER_FUNC(udp, struct bpf_iter_meta *meta, > struct udp_sock *udp_sk, uid_t uid, int bucket) > > +static int bpf_iter_udp_realloc_batch(struct bpf_udp_iter_state *iter, > + unsigned int new_batch_sz) > +{ > + struct sock **new_batch; > + > + new_batch = kvmalloc_array(new_batch_sz, sizeof(*new_batch), > + GFP_USER | __GFP_NOWARN); > + if (!new_batch) > + return -ENOMEM; > + > + bpf_iter_udp_put_batch(iter); > + kvfree(iter->batch); > + iter->batch = new_batch; > + iter->max_sk = new_batch_sz; > + > + return 0; > +} > + > +#define INIT_BATCH_SZ 16 > + > static int bpf_iter_init_udp(void *priv_data, struct bpf_iter_aux_info *aux) > { > - return bpf_iter_init_seq_net(priv_data, aux); > + struct bpf_udp_iter_state *iter = priv_data; > + int ret; > + > + ret = bpf_iter_init_seq_net(priv_data, aux); > + if (ret) > + return ret; > + > + ret = bpf_iter_udp_realloc_batch(iter, INIT_BATCH_SZ); > + if (ret) { > + bpf_iter_fini_seq_net(priv_data); > + return ret; nit. remove this "return ret;" statement. Others lgtm. I will continue with the rest of the patchset tomorrow. > + } > + > + return ret; > } > > static void bpf_iter_fini_udp(void *priv_data) > { > + struct bpf_udp_iter_state *iter = priv_data; > + > bpf_iter_fini_seq_net(priv_data); > + kvfree(iter->batch); > } > > static const struct bpf_iter_seq_info udp_seq_info = { > .seq_ops = &bpf_iter_udp_seq_ops, > .init_seq_private = bpf_iter_init_udp, > .fini_seq_private = bpf_iter_fini_udp, > - .seq_priv_size = sizeof(struct udp_iter_state), > + .seq_priv_size = sizeof(struct bpf_udp_iter_state), > }; > > static struct bpf_iter_reg udp_reg_info = {