From patchwork Tue Dec 10 13:39:41 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Durrant X-Patchwork-Id: 299470 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id F31262C0373 for ; Wed, 11 Dec 2013 09:21:44 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753607Ab3LJNjx (ORCPT ); Tue, 10 Dec 2013 08:39:53 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:27072 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752376Ab3LJNju (ORCPT ); Tue, 10 Dec 2013 08:39:50 -0500 X-IronPort-AV: E=Sophos;i="4.93,865,1378857600"; d="scan'208";a="80430477" Received: from accessns.citrite.net (HELO FTLPEX01CL03.citrite.net) ([10.9.154.239]) by FTLPIPO02.CITRIX.COM with ESMTP; 10 Dec 2013 13:39:48 +0000 Received: from ukmail1.uk.xensource.com (10.80.16.128) by smtprelay.citrix.com (10.13.107.80) with Microsoft SMTP Server id 14.2.342.4; Tue, 10 Dec 2013 08:39:47 -0500 Received: from etemp.uk.xensource.com ([10.80.228.66] helo=etemp.uk.xensource.com.) by ukmail1.uk.xensource.com with esmtp (Exim 4.69) (envelope-from ) id 1VqNXP-0004In-FL; Tue, 10 Dec 2013 13:39:47 +0000 From: Paul Durrant To: , CC: Paul Durrant , Wei Liu , "Ian Campbell" , David Vrabel Subject: [PATCH net v3 1/2] xen-netback: napi: fix abuse of budget Date: Tue, 10 Dec 2013 13:39:41 +0000 Message-ID: <1386682782-7052-2-git-send-email-paul.durrant@citrix.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1386682782-7052-1-git-send-email-paul.durrant@citrix.com> References: <1386682782-7052-1-git-send-email-paul.durrant@citrix.com> MIME-Version: 1.0 X-DLP: MIA2 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org netback seems to be somewhat confused about the napi budget parameter. The parameter is supposed to limit the number of skbs processed in each poll, but netback has this confused with grant operations. This patch fixes that, properly limiting the work done in each poll. Note that this limit makes sure we do not process any more data from the shared ring than we intend to pass back from the poll. This is important to prevent tx_queue potentially growing without bound. Signed-off-by: Paul Durrant Cc: Wei Liu Cc: Ian Campbell Cc: David Vrabel --- drivers/net/xen-netback/netback.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 43341b8..83b4e5b 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -1351,14 +1351,15 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size) return false; } -static unsigned xenvif_tx_build_gops(struct xenvif *vif) +static unsigned xenvif_tx_build_gops(struct xenvif *vif, int budget) { struct gnttab_copy *gop = vif->tx_copy_ops, *request_gop; struct sk_buff *skb; int ret; while ((nr_pending_reqs(vif) + XEN_NETBK_LEGACY_SLOTS_MAX - < MAX_PENDING_REQS)) { + < MAX_PENDING_REQS) && + (skb_queue_len(&vif->tx_queue) < budget)) { struct xen_netif_tx_request txreq; struct xen_netif_tx_request txfrags[XEN_NETBK_LEGACY_SLOTS_MAX]; struct page *page; @@ -1520,14 +1521,13 @@ static unsigned xenvif_tx_build_gops(struct xenvif *vif) } -static int xenvif_tx_submit(struct xenvif *vif, int budget) +static int xenvif_tx_submit(struct xenvif *vif) { struct gnttab_copy *gop = vif->tx_copy_ops; struct sk_buff *skb; int work_done = 0; - while (work_done < budget && - (skb = __skb_dequeue(&vif->tx_queue)) != NULL) { + while ((skb = __skb_dequeue(&vif->tx_queue)) != NULL) { struct xen_netif_tx_request *txp; u16 pending_idx; unsigned data_len; @@ -1602,14 +1602,14 @@ int xenvif_tx_action(struct xenvif *vif, int budget) if (unlikely(!tx_work_todo(vif))) return 0; - nr_gops = xenvif_tx_build_gops(vif); + nr_gops = xenvif_tx_build_gops(vif, budget); if (nr_gops == 0) return 0; gnttab_batch_copy(vif->tx_copy_ops, nr_gops); - work_done = xenvif_tx_submit(vif, nr_gops); + work_done = xenvif_tx_submit(vif); return work_done; }