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 E27F7C76195 for ; Mon, 27 Mar 2023 22:28:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229464AbjC0W2i (ORCPT ); Mon, 27 Mar 2023 18:28:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229456AbjC0W2i (ORCPT ); Mon, 27 Mar 2023 18:28:38 -0400 Received: from out-44.mta0.migadu.com (out-44.mta0.migadu.com [IPv6:2001:41d0:1004:224b::2c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F163E1997 for ; Mon, 27 Mar 2023 15:28:35 -0700 (PDT) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1679956112; 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=qNXZmzkfQu7AFIvuVw4d1vt9wu+hspBdl2iQD8FXFZU=; b=JNKqZrnVVhzIWiqxjEIwGLzCyCAsW/bifF/xQJcY0mvdrcOFTSHEP6goHipLG5cHD42bQZ KEhU+xGhWqUwWzkKb0F//gnF5u1pH1YHRVYlk37uV+lUdbe/g1QGkXl10nScNdoyW3j+2N CJV5CpI/1y7KPPF2B1x4Ih8Oi83J81I= Date: Mon, 27 Mar 2023 15:28:28 -0700 MIME-Version: 1.0 Subject: Re: [PATCH v4 bpf-next 1/4] bpf: Implement batching in UDP 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: <20230323200633.3175753-1-aditi.ghag@isovalent.com> <20230323200633.3175753-2-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: <20230323200633.3175753-2-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 3/23/23 1:06 PM, 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 > --- > include/net/udp.h | 1 + > net/ipv4/udp.c | 255 ++++++++++++++++++++++++++++++++++++++++++++-- > 2 files changed, 247 insertions(+), 9 deletions(-) > > diff --git a/include/net/udp.h b/include/net/udp.h > index de4b528522bb..d2999447d3f2 100644 > --- a/include/net/udp.h > +++ b/include/net/udp.h > @@ -437,6 +437,7 @@ struct udp_seq_afinfo { > struct udp_iter_state { > struct seq_net_private p; > int bucket; > + int offset; offset should be moved to 'struct bpf_udp_iter_state' instead. It is specific to bpf_iter only. > struct udp_seq_afinfo *bpf_seq_afinfo; > }; > > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c > index c605d171eb2d..58c620243e47 100644 > --- a/net/ipv4/udp.c > +++ b/net/ipv4/udp.c > @@ -3152,6 +3152,171 @@ 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; > + struct sock **batch; > + bool st_bucket_done; > +}; > + > +static unsigned short seq_file_family(const struct seq_file *seq); > +static int bpf_iter_udp_realloc_batch(struct bpf_udp_iter_state *iter, > + unsigned int new_batch_sz); > + > +static inline bool seq_sk_match(struct seq_file *seq, const struct sock *sk) > +{ > + unsigned short family = seq_file_family(seq); > + > + /* AF_UNSPEC is used as a match all */ > + return ((family == AF_UNSPEC || family == sk->sk_family) && > + net_eq(sock_net(sk), seq_file_net(seq))); > +} > + > +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 = state->bpf_seq_afinfo; > + struct udp_table *udptable; > + struct sock *first_sk = NULL; > + struct sock *sk; > + unsigned int bucket_sks = 0; > + bool resized = false; > + int offset = 0; > + int new_offset; > + > + /* The current batch is done, so advance the bucket. */ > + if (iter->st_bucket_done) { > + state->bucket++; > + state->offset = 0; > + } > + > + udptable = udp_get_table_afinfo(afinfo, net); > + > + if (state->bucket > udptable->mask) { > + state->bucket = 0; > + state->offset = 0; > + return NULL; > + } > + > +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; > + first_sk = NULL; > + bucket_sks = 0; > + offset = state->offset; > + new_offset = offset; > + > + for (; state->bucket <= udptable->mask; state->bucket++) { > + struct udp_hslot *hslot = &udptable->hash[state->bucket]; Use udptable->hash"2" which is hashed by addr and port. It will help to get a smaller batch. It was the comment given in v2. > + > + if (hlist_empty(&hslot->head)) { > + offset = 0; > + continue; > + } > + > + spin_lock_bh(&hslot->lock); > + /* Resume from the last saved position in a bucket before > + * iterator was stopped. > + */ > + while (offset-- > 0) { > + sk_for_each(sk, &hslot->head) > + continue; > + } hmm... how does the above while loop and sk_for_each loop actually work? > + sk_for_each(sk, &hslot->head) { Here starts from the beginning of the hslot->head again. doesn't look right also. Am I missing something here? > + if (seq_sk_match(seq, sk)) { > + if (!first_sk) > + first_sk = sk; > + if (iter->end_sk < iter->max_sk) { > + sock_hold(sk); > + iter->batch[iter->end_sk++] = sk; > + } > + bucket_sks++; > + } > + new_offset++; And this new_offset is outside of seq_sk_match, so it is not counting for the seq_file_net(seq) netns alone. > + } > + spin_unlock_bh(&hslot->lock); > + > + if (first_sk) > + break; > + > + /* Reset the current bucket's offset before moving to the next bucket. */ > + offset = 0; > + new_offset = 0; > + } > + > + /* All done: no batch made. */ > + if (!first_sk) > + goto ret; > + > + if (iter->end_sk == bucket_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; > + } > + if (!resized && !bpf_iter_udp_realloc_batch(iter, bucket_sks * 3 / 2)) { > + resized = true; > + /* Go back to the previous bucket to resize its batch. */ > + state->bucket--; > + goto again; > + } > +ret: > + state->offset = new_offset; > + return first_sk; > +} > + > +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 udp_iter_state *state = &iter->state; > + 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++]); > + ++state->offset; but then, if I read it correctly, this offset counting is only for netns specific to seq_file_net(seq) because batch is specific to seq_file_net(net). Is it going to work? > + } > + > + /* 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); > + } > + > + ++*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) > { > @@ -3172,18 +3337,38 @@ static int bpf_iter_udp_seq_show(struct seq_file *seq, void *v) > struct bpf_prog *prog; > struct sock *sk = v; > uid_t uid; > + bool slow; > + int rc; > > if (v == SEQ_START_TOKEN) > return 0; > > + slow = lock_sock_fast(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: > + unlock_sock_fast(sk, slow); > + return rc; > +} > + > +static void bpf_iter_udp_unref_batch(struct bpf_udp_iter_state *iter) nit. Please use the same naming as in tcp-iter and unix-iter, so bpf_iter_udp_put_batch(). > +{ > + 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; > > @@ -3194,15 +3379,31 @@ 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_unref_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, > }; > + > +static unsigned short seq_file_family(const struct seq_file *seq) > +{ > + const struct udp_seq_afinfo *afinfo; > + > + /* BPF iterator: bpf programs to filter sockets. */ > + if (seq->op == &bpf_iter_udp_seq_ops) > + return AF_UNSPEC; > + > + /* Proc fs iterator */ > + afinfo = pde_data(file_inode(seq->file)); > + return afinfo->family; > +} > #endif > > const struct seq_operations udp_seq_ops = { > @@ -3413,9 +3614,30 @@ 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_unref_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) > { > - struct udp_iter_state *st = priv_data; > + struct bpf_udp_iter_state *iter = priv_data; > + struct udp_iter_state *st = &iter->state; > struct udp_seq_afinfo *afinfo; > int ret; > > @@ -3427,24 +3649,39 @@ static int bpf_iter_init_udp(void *priv_data, struct bpf_iter_aux_info *aux) > afinfo->udp_table = NULL; > st->bpf_seq_afinfo = afinfo; > ret = bpf_iter_init_seq_net(priv_data, aux); > - if (ret) > + if (ret) { > kfree(afinfo); > + return ret; > + } > + ret = bpf_iter_udp_realloc_batch(iter, INIT_BATCH_SZ); > + if (ret) { > + bpf_iter_fini_seq_net(priv_data); > + return ret; > + } > + iter->cur_sk = 0; > + iter->end_sk = 0; > + iter->st_bucket_done = false; > + st->bucket = 0; > + st->offset = 0; From looking at the tcp and unix counter part, I don't think this zeroings is necessary. > + > return ret; > } > > static void bpf_iter_fini_udp(void *priv_data) > { > - struct udp_iter_state *st = priv_data; > + struct bpf_udp_iter_state *iter = priv_data; > + struct udp_iter_state *st = &iter->state; > > - kfree(st->bpf_seq_afinfo); The st->bpf_seq_afinfo should no longer be needed. Please remove it from 'struct udp_iter_state'. The other AF_UNSPEC test in the existing udp_get_{first,next,...} should be cleaned up to use the refactored seq_sk_match() also. These two changes should be done as the first one (or two?) cleanup patches before the actual udp batching patch. The tcp-iter-batching patch set could be a reference point on how the patch set could be structured. > bpf_iter_fini_seq_net(priv_data); > + kfree(st->bpf_seq_afinfo); > + 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 = {