From patchwork Wed May 17 05:22:35 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Fastabend X-Patchwork-Id: 13244213 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 447E08BE0; Wed, 17 May 2023 05:23:12 +0000 (UTC) Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E37AD448A; Tue, 16 May 2023 22:22:57 -0700 (PDT) Received: by mail-pl1-x632.google.com with SMTP id d9443c01a7336-1ae408f4d1aso3668235ad.0; Tue, 16 May 2023 22:22:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1684300977; x=1686892977; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=AMWQXrGcXhHgmJZ5RnEojce3chjmU+rt7GqrTxtYxbI=; b=sB20xARYeZerNV0bZVpO+CIptoUkhcXuYgdqiYez2/gJHy9QbTH4Za66p9b45q5hIL LLWeUx2RdMUjHWdDiK3ovC4TXZ2Elf83nSmk+f0KSNzVNL24ng7zxfab5Efr++cHIBMw Rish94AgLXFWl0I7ah3fBmLfqwJmWOX0T6vE14fRX2hAs05zX/K5N6Us4mlfzeK8Addg 5WJTKzCtab5kJQyPrgL5lE5r8IesWFC5eG/NAhbRf+fu1bx+ogDRVuHXwmsQm03/ITFs VtVBqBvIi/tJUhFTT/r6y/2PbF8q75QMMZm8NXp8ijmawD3NIdkBTLXw7zwUUqBgpCse RI3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684300977; x=1686892977; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=AMWQXrGcXhHgmJZ5RnEojce3chjmU+rt7GqrTxtYxbI=; b=cIomk1oKty0Wu5+cEN0GMGmgCepMmp18bfN+l9rukqxvmcLoag67+LOJrbc3vUIsrr kBvK3dc6Auzr1jyqt8y7PIuFlwntxHUh9TocoJeF9dADON6iUWBMkRZdBE5ECvgIiKt5 iXuG5Y7XtgXwXFsyrmiD231iS0gBdVAhaa9S6y2rAb4qNwBWf21ct7FVMEl0kzMcw7J7 PozySgxPyNGEIBRoEFoNK2zUE9t3bipTvdmj/v+cSQWzPigCrSb/orULBt7KpmrmBRm6 0mBgq+VwduLz169q+WHPkyG25XZaxdFvCajkWz7iAVkw8J0UImPjLQnonBbO2nnqgoOt 1+Pw== X-Gm-Message-State: AC+VfDyOl3QN3P/pgqInQckRG7PUJgi7kYOAA8DmrjZ303Wdrp/olokk 1sNvg6qLC81N2qgrnQe7mfAodIJURWY= X-Google-Smtp-Source: ACHHUZ40FygeNkOFuw/sIJWyDlQq9i7b00Z5DB3wwEamHf3QLmfIvAMfFn4sd5YdjEx2uWCqxYpJzg== X-Received: by 2002:a17:902:f54f:b0:1ac:750e:33ef with SMTP id h15-20020a170902f54f00b001ac750e33efmr42452729plf.3.1684300977089; Tue, 16 May 2023 22:22:57 -0700 (PDT) Received: from john.lan ([98.97.37.198]) by smtp.gmail.com with ESMTPSA id n11-20020a17090a2fcb00b0023cfdbb6496sm581779pjm.1.2023.05.16.22.22.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 May 2023 22:22:56 -0700 (PDT) From: John Fastabend To: jakub@cloudflare.com, daniel@iogearbox.net Cc: john.fastabend@gmail.com, bpf@vger.kernel.org, netdev@vger.kernel.org, edumazet@google.com, ast@kernel.org, andrii@kernel.org, will@isovalent.com Subject: [PATCH bpf v8 04/13] bpf: sockmap, improved check for empty queue Date: Tue, 16 May 2023 22:22:35 -0700 Message-Id: <20230517052244.294755-5-john.fastabend@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20230517052244.294755-1-john.fastabend@gmail.com> References: <20230517052244.294755-1-john.fastabend@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net We noticed some rare sk_buffs were stepping past the queue when system was under memory pressure. The general theory is to skip enqueueing sk_buffs when its not necessary which is the normal case with a system that is properly provisioned for the task, no memory pressure and enough cpu assigned. But, if we can't allocate memory due to an ENOMEM error when enqueueing the sk_buff into the sockmap receive queue we push it onto a delayed workqueue to retry later. When a new sk_buff is received we then check if that queue is empty. However, there is a problem with simply checking the queue length. When a sk_buff is being processed from the ingress queue but not yet on the sockmap msg receive queue its possible to also recv a sk_buff through normal path. It will check the ingress queue which is zero and then skip ahead of the pkt being processed. Previously we used sock lock from both contexts which made the problem harder to hit, but not impossible. To fix instead of popping the skb from the queue entirely we peek the skb from the queue and do the copy there. This ensures checks to the queue length are non-zero while skb is being processed. Then finally when the entire skb has been copied to user space queue or another socket we pop it off the queue. This way the queue length check allows bypassing the queue only after the list has been completely processed. To reproduce issue we run NGINX compliance test with sockmap running and observe some flakes in our testing that we attributed to this issue. Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()") Tested-by: William Findlay Suggested-by: Jakub Sitnicki Signed-off-by: John Fastabend Reviewed-by: Jakub Sitnicki --- include/linux/skmsg.h | 1 - net/core/skmsg.c | 32 ++++++++------------------------ 2 files changed, 8 insertions(+), 25 deletions(-) diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h index 904ff9a32ad6..054d7911bfc9 100644 --- a/include/linux/skmsg.h +++ b/include/linux/skmsg.h @@ -71,7 +71,6 @@ struct sk_psock_link { }; struct sk_psock_work_state { - struct sk_buff *skb; u32 len; u32 off; }; diff --git a/net/core/skmsg.c b/net/core/skmsg.c index 76ff15f8bb06..bcd45a99a3db 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -622,16 +622,12 @@ static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb, static void sk_psock_skb_state(struct sk_psock *psock, struct sk_psock_work_state *state, - struct sk_buff *skb, int len, int off) { spin_lock_bh(&psock->ingress_lock); if (sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED)) { - state->skb = skb; state->len = len; state->off = off; - } else { - sock_drop(psock->sk, skb); } spin_unlock_bh(&psock->ingress_lock); } @@ -642,23 +638,17 @@ static void sk_psock_backlog(struct work_struct *work) struct sk_psock *psock = container_of(dwork, struct sk_psock, work); struct sk_psock_work_state *state = &psock->work_state; struct sk_buff *skb = NULL; + u32 len = 0, off = 0; bool ingress; - u32 len, off; int ret; mutex_lock(&psock->work_mutex); - if (unlikely(state->skb)) { - spin_lock_bh(&psock->ingress_lock); - skb = state->skb; + if (unlikely(state->len)) { len = state->len; off = state->off; - state->skb = NULL; - spin_unlock_bh(&psock->ingress_lock); } - if (skb) - goto start; - while ((skb = skb_dequeue(&psock->ingress_skb))) { + while ((skb = skb_peek(&psock->ingress_skb))) { len = skb->len; off = 0; if (skb_bpf_strparser(skb)) { @@ -667,7 +657,6 @@ static void sk_psock_backlog(struct work_struct *work) off = stm->offset; len = stm->full_len; } -start: ingress = skb_bpf_ingress(skb); skb_bpf_redirect_clear(skb); do { @@ -677,8 +666,7 @@ static void sk_psock_backlog(struct work_struct *work) len, ingress); if (ret <= 0) { if (ret == -EAGAIN) { - sk_psock_skb_state(psock, state, skb, - len, off); + sk_psock_skb_state(psock, state, len, off); /* Delay slightly to prioritize any * other work that might be here. @@ -690,15 +678,16 @@ static void sk_psock_backlog(struct work_struct *work) /* Hard errors break pipe and stop xmit. */ sk_psock_report_error(psock, ret ? -ret : EPIPE); sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED); - sock_drop(psock->sk, skb); goto end; } off += ret; len -= ret; } while (len); - if (!ingress) + skb = skb_dequeue(&psock->ingress_skb); + if (!ingress) { kfree_skb(skb); + } } end: mutex_unlock(&psock->work_mutex); @@ -791,11 +780,6 @@ static void __sk_psock_zap_ingress(struct sk_psock *psock) skb_bpf_redirect_clear(skb); sock_drop(psock->sk, skb); } - kfree_skb(psock->work_state.skb); - /* We null the skb here to ensure that calls to sk_psock_backlog - * do not pick up the free'd skb. - */ - psock->work_state.skb = NULL; __sk_psock_purge_ingress_msg(psock); } @@ -814,7 +798,6 @@ void sk_psock_stop(struct sk_psock *psock) spin_lock_bh(&psock->ingress_lock); sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED); sk_psock_cork_free(psock); - __sk_psock_zap_ingress(psock); spin_unlock_bh(&psock->ingress_lock); } @@ -829,6 +812,7 @@ static void sk_psock_destroy(struct work_struct *work) sk_psock_done_strp(psock); cancel_delayed_work_sync(&psock->work); + __sk_psock_zap_ingress(psock); mutex_destroy(&psock->work_mutex); psock_progs_drop(&psock->progs);