From patchwork Mon Nov 23 17:56:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= X-Patchwork-Id: 11925903 X-Patchwork-Delegate: bpf@iogearbox.net 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=-15.7 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,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 91728C2D0E4 for ; Mon, 23 Nov 2020 17:56:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 450BD2075A for ; Mon, 23 Nov 2020 17:56:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Vy3Ex6kT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732492AbgKWR4O (ORCPT ); Mon, 23 Nov 2020 12:56:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729604AbgKWR4O (ORCPT ); Mon, 23 Nov 2020 12:56:14 -0500 Received: from mail-pg1-x541.google.com (mail-pg1-x541.google.com [IPv6:2607:f8b0:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9422CC0613CF; Mon, 23 Nov 2020 09:56:14 -0800 (PST) Received: by mail-pg1-x541.google.com with SMTP id w4so14914010pgg.13; Mon, 23 Nov 2020 09:56:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=py5JSSlXJWcBrQyWwWpRNK4T/vAv6z6ZKSuuqxdy+GI=; b=Vy3Ex6kTxISbSehx1V6iapmkiA2wFujIN7sbtzzuTfrcAkZJZpsN6hTXRShAQtn5UJ qj7SepGSHvll+bePskpvjZGYJmkV5cb5m1PKI/W8Q6pHKj2NlUKwR+Re9yYppVND3xoY +dkISyCr7o1JXX0HH2Qd3wUnEa/ETFAgYQ8q3UmlMgC56lQtuvme/nx4AxmrG0lCnJTM NNGx6aygUu0janeRnpB01qYw0ZxV4V9mknGXO//azAAMAqqqsKwtOnh84aAVKWbfe1A5 5TM1gbFQZyLxPEyoR/H2UfsVHYHOhMx6rvXbiTM31i0M3ofckVCFB1aNnrofG96hVFOW OClw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=py5JSSlXJWcBrQyWwWpRNK4T/vAv6z6ZKSuuqxdy+GI=; b=Ml79WI53E70zU/AsvdlMCu8OPJvBtX378W+75wY43JwIfiRj52TQl6/sncpQ8kmrKt N6L9Ve9sJ8RiNGFA+QeWQJJ+y9kfNvoA8rX/iBqETHwtILrInNz5c3MZvAbulqvhZhZU d3+SUPpY4Iu5r0fDNrNeoyqKRfRP2t8afFdyUVNI0RlhdoFVqA6CNO6eLZZyaIWano2o InwJUXRAXjIhgQWeT2j06agK1RQUmSBH0kC6/kGoFMMPJm5zSXUF6Rw4/RELJA1l8P1A JBiym0F8hKrneE/C/94EHFcOE28NV5DzB2KIuw+DC1fFeK05UTCZSJHsarh7oseuQdw/ WuSw== X-Gm-Message-State: AOAM531tjTa72O2LuCwJdvlQBvrb/xMsHfbL19M4oFvIg3YVzFDqBk1e HV1LQAva18ANh0Cl2Cs6V3qo2Yxv9f7RRVn0 X-Google-Smtp-Source: ABdhPJxDTEDp+vPd4v7YrUMs9vuZSE3UyxwzBOlsZN6gCiHjUSOvl2qfj4WixGlLMmWQBjrnBCvTcg== X-Received: by 2002:aa7:982e:0:b029:18b:6372:d445 with SMTP id q14-20020aa7982e0000b029018b6372d445mr466612pfl.31.1606154174168; Mon, 23 Nov 2020 09:56:14 -0800 (PST) Received: from btopel-mobl.ger.intel.com ([192.55.54.40]) by smtp.gmail.com with ESMTPSA id y5sm12903423pfc.165.2020.11.23.09.56.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Nov 2020 09:56:12 -0800 (PST) From: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= To: ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org Cc: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , jonathan.lemon@gmail.com, yhs@fb.com, weqaar.janjua@gmail.com, magnus.karlsson@intel.com, weqaar.a.janjua@intel.com Subject: [PATCH bpf v2] net, xsk: Avoid taking multiple skbuff references Date: Mon, 23 Nov 2020 18:56:00 +0100 Message-Id: <20201123175600.146255-1-bjorn.topel@gmail.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Björn Töpel Commit 642e450b6b59 ("xsk: Do not discard packet when NETDEV_TX_BUSY") addressed the problem that packets were discarded from the Tx AF_XDP ring, when the driver returned NETDEV_TX_BUSY. Part of the fix was bumping the skbuff reference count, so that the buffer would not be freed by dev_direct_xmit(). A reference count larger than one means that the skbuff is "shared", which is not the case. If the "shared" skbuff is sent to the generic XDP receive path, netif_receive_generic_xdp(), and pskb_expand_head() is entered the BUG_ON(skb_shared(skb)) will trigger. This patch adds a variant to dev_direct_xmit(), __dev_direct_xmit(), where a user can select the skbuff free policy. This allows AF_XDP to avoid bumping the reference count, but still keep the NETDEV_TX_BUSY behavior. Reported-by: Yonghong Song Fixes: 642e450b6b59 ("xsk: Do not discard packet when NETDEV_TX_BUSY") Signed-off-by: Björn Töpel --- v2: Removed the bool parameter, and inlined dev_direct_xmit(). (Daniel) --- include/linux/netdevice.h | 11 ++++++++++- net/core/dev.c | 8 ++------ net/xdp/xsk.c | 8 +------- 3 files changed, 13 insertions(+), 14 deletions(-) base-commit: 178648916e73e00de83150eb0c90c0d3a977a46a diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 964b494b0e8d..bd841f31dfab 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -2815,7 +2815,16 @@ u16 dev_pick_tx_cpu_id(struct net_device *dev, struct sk_buff *skb, struct net_device *sb_dev); int dev_queue_xmit(struct sk_buff *skb); int dev_queue_xmit_accel(struct sk_buff *skb, struct net_device *sb_dev); -int dev_direct_xmit(struct sk_buff *skb, u16 queue_id); +int __dev_direct_xmit(struct sk_buff *skb, u16 queue_id); +static inline int dev_direct_xmit(struct sk_buff *skb, u16 queue_id) +{ + int ret; + + ret = __dev_direct_xmit(skb, queue_id); + if (!dev_xmit_complete(ret)) + kfree_skb(skb); + return ret; +} int register_netdevice(struct net_device *dev); void unregister_netdevice_queue(struct net_device *dev, struct list_head *head); void unregister_netdevice_many(struct list_head *head); diff --git a/net/core/dev.c b/net/core/dev.c index 82dc6b48e45f..8588ade790cb 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4180,7 +4180,7 @@ int dev_queue_xmit_accel(struct sk_buff *skb, struct net_device *sb_dev) } EXPORT_SYMBOL(dev_queue_xmit_accel); -int dev_direct_xmit(struct sk_buff *skb, u16 queue_id) +int __dev_direct_xmit(struct sk_buff *skb, u16 queue_id) { struct net_device *dev = skb->dev; struct sk_buff *orig_skb = skb; @@ -4210,17 +4210,13 @@ int dev_direct_xmit(struct sk_buff *skb, u16 queue_id) dev_xmit_recursion_dec(); local_bh_enable(); - - if (!dev_xmit_complete(ret)) - kfree_skb(skb); - return ret; drop: atomic_long_inc(&dev->tx_dropped); kfree_skb_list(skb); return NET_XMIT_DROP; } -EXPORT_SYMBOL(dev_direct_xmit); +EXPORT_SYMBOL(__dev_direct_xmit); /************************************************************************* * Receiver routines diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 5a6cdf7b320d..b7b039bd9d03 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -411,11 +411,7 @@ static int xsk_generic_xmit(struct sock *sk) skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr; skb->destructor = xsk_destruct_skb; - /* Hinder dev_direct_xmit from freeing the packet and - * therefore completing it in the destructor - */ - refcount_inc(&skb->users); - err = dev_direct_xmit(skb, xs->queue_id); + err = __dev_direct_xmit(skb, xs->queue_id); if (err == NETDEV_TX_BUSY) { /* Tell user-space to retry the send */ skb->destructor = sock_wfree; @@ -429,12 +425,10 @@ static int xsk_generic_xmit(struct sock *sk) /* Ignore NET_XMIT_CN as packet might have been sent */ if (err == NET_XMIT_DROP) { /* SKB completed but not sent */ - kfree_skb(skb); err = -EBUSY; goto out; } - consume_skb(skb); sent_frame = true; }