From patchwork Thu Oct 15 09:46:53 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eelco Chaudron X-Patchwork-Id: 11838835 X-Patchwork-Delegate: kuba@kernel.org 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=-9.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 BD3E9C433DF for ; Thu, 15 Oct 2020 09:47:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50B182224A for ; Thu, 15 Oct 2020 09:47:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="IX+Y40xe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388920AbgJOJrI (ORCPT ); Thu, 15 Oct 2020 05:47:08 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:58515 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388789AbgJOJrI (ORCPT ); Thu, 15 Oct 2020 05:47:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602755226; 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; bh=1TaUMLO70lMW7u1wsGwZHTX2AFWks1AkvWQYCuOPHPI=; b=IX+Y40xezqY6ayI32x08+OKTZ7+bVpWAojYIh8uPWd9qZ2kvobGfWPlDE9rwiBCCW6EwSt A7v2impvc7WLrg9rcMeUJ0bk4SbKVCr9n6zZpyUdA8tWOuspZnpSg3F2CJvLKkl5ozGSma Vl0pyO/j3/FiNNmg4i3dmzIx/j45ZGs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-495-bk2-abcnNbWyLUX6ZAiRJQ-1; Thu, 15 Oct 2020 05:47:03 -0400 X-MC-Unique: bk2-abcnNbWyLUX6ZAiRJQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EB5C28030DE; Thu, 15 Oct 2020 09:47:01 +0000 (UTC) Received: from ebuild.redhat.com (ovpn-115-61.ams2.redhat.com [10.36.115.61]) by smtp.corp.redhat.com (Postfix) with ESMTP id 87239610F3; Thu, 15 Oct 2020 09:46:58 +0000 (UTC) From: Eelco Chaudron To: netdev@vger.kernel.org Cc: davem@davemloft.net, dev@openvswitch.org, kuba@kernel.org, pabeni@redhat.com, pshelar@ovn.org, jlelli@redhat.com, bigeasy@linutronix.de Subject: [PATCH net v2] net: openvswitch: fix to make sure flow_lookup() is not preempted Date: Thu, 15 Oct 2020 11:46:53 +0200 Message-Id: <160275519174.566500.6537031776378218151.stgit@ebuild> User-Agent: StGit/0.21 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org The flow_lookup() function uses per CPU variables, which must not be preempted. However, this is fine in the general napi use case where the local BH is disabled. But, it's also called in the netlink context, which is preemptible. The below patch makes sure that even in the netlink path, preemption is disabled. In addition, the u64_stats_update_begin() sync point was not protected, making the sync point part of the per CPU variable fixed this. Fixes: eac87c413bf9 ("net: openvswitch: reorder masks array based on usage") Reported-by: Juri Lelli Signed-off-by: Eelco Chaudron --- v2: - Add u64_stats_update_begin() sync point protection - Moved patch to net from net-next branch net/openvswitch/flow_table.c | 56 +++++++++++++++++++++++++----------------- net/openvswitch/flow_table.h | 8 +++++- 2 files changed, 39 insertions(+), 25 deletions(-) diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c index e2235849a57e..d90b4af6f539 100644 --- a/net/openvswitch/flow_table.c +++ b/net/openvswitch/flow_table.c @@ -172,7 +172,7 @@ static struct table_instance *table_instance_alloc(int new_size) static void __mask_array_destroy(struct mask_array *ma) { - free_percpu(ma->masks_usage_cntr); + free_percpu(ma->masks_usage_stats); kfree(ma); } @@ -196,15 +196,15 @@ static void tbl_mask_array_reset_counters(struct mask_array *ma) ma->masks_usage_zero_cntr[i] = 0; for_each_possible_cpu(cpu) { - u64 *usage_counters = per_cpu_ptr(ma->masks_usage_cntr, - cpu); + struct mask_array_stats *stats; unsigned int start; u64 counter; + stats = per_cpu_ptr(ma->masks_usage_stats, cpu); do { - start = u64_stats_fetch_begin_irq(&ma->syncp); - counter = usage_counters[i]; - } while (u64_stats_fetch_retry_irq(&ma->syncp, start)); + start = u64_stats_fetch_begin_irq(&stats->syncp); + counter = stats->usage_cntrs[i]; + } while (u64_stats_fetch_retry_irq(&stats->syncp, start)); ma->masks_usage_zero_cntr[i] += counter; } @@ -227,9 +227,10 @@ static struct mask_array *tbl_mask_array_alloc(int size) sizeof(struct sw_flow_mask *) * size); - new->masks_usage_cntr = __alloc_percpu(sizeof(u64) * size, - __alignof__(u64)); - if (!new->masks_usage_cntr) { + new->masks_usage_stats = __alloc_percpu(sizeof(struct mask_array_stats) + + sizeof(u64) * size, + __alignof__(u64)); + if (!new->masks_usage_stats) { kfree(new); return NULL; } @@ -732,7 +733,7 @@ static struct sw_flow *flow_lookup(struct flow_table *tbl, u32 *n_cache_hit, u32 *index) { - u64 *usage_counters = this_cpu_ptr(ma->masks_usage_cntr); + struct mask_array_stats *stats = this_cpu_ptr(ma->masks_usage_stats); struct sw_flow *flow; struct sw_flow_mask *mask; int i; @@ -742,9 +743,9 @@ static struct sw_flow *flow_lookup(struct flow_table *tbl, if (mask) { flow = masked_flow_lookup(ti, key, mask, n_mask_hit); if (flow) { - u64_stats_update_begin(&ma->syncp); - usage_counters[*index]++; - u64_stats_update_end(&ma->syncp); + u64_stats_update_begin(&stats->syncp); + stats->usage_cntrs[*index]++; + u64_stats_update_end(&stats->syncp); (*n_cache_hit)++; return flow; } @@ -763,9 +764,9 @@ static struct sw_flow *flow_lookup(struct flow_table *tbl, flow = masked_flow_lookup(ti, key, mask, n_mask_hit); if (flow) { /* Found */ *index = i; - u64_stats_update_begin(&ma->syncp); - usage_counters[*index]++; - u64_stats_update_end(&ma->syncp); + u64_stats_update_begin(&stats->syncp); + stats->usage_cntrs[*index]++; + u64_stats_update_end(&stats->syncp); return flow; } } @@ -851,9 +852,17 @@ struct sw_flow *ovs_flow_tbl_lookup(struct flow_table *tbl, struct mask_array *ma = rcu_dereference_ovsl(tbl->mask_array); u32 __always_unused n_mask_hit; u32 __always_unused n_cache_hit; + struct sw_flow *flow; u32 index = 0; - return flow_lookup(tbl, ti, ma, key, &n_mask_hit, &n_cache_hit, &index); + /* This function gets called trough the netlink interface and therefore + * is preemptible. However, flow_lookup() function needs to be called + * with preemption disabled due to CPU specific variables. + */ + local_bh_disable(); + flow = flow_lookup(tbl, ti, ma, key, &n_mask_hit, &n_cache_hit, &index); + local_bh_enable(); + return flow; } struct sw_flow *ovs_flow_tbl_lookup_exact(struct flow_table *tbl, @@ -1109,7 +1118,6 @@ void ovs_flow_masks_rebalance(struct flow_table *table) for (i = 0; i < ma->max; i++) { struct sw_flow_mask *mask; - unsigned int start; int cpu; mask = rcu_dereference_ovsl(ma->masks[i]); @@ -1120,14 +1128,16 @@ void ovs_flow_masks_rebalance(struct flow_table *table) masks_and_count[i].counter = 0; for_each_possible_cpu(cpu) { - u64 *usage_counters = per_cpu_ptr(ma->masks_usage_cntr, - cpu); + struct mask_array_stats *stats; + unsigned int start; u64 counter; + stats = per_cpu_ptr(ma->masks_usage_stats, cpu); do { - start = u64_stats_fetch_begin_irq(&ma->syncp); - counter = usage_counters[i]; - } while (u64_stats_fetch_retry_irq(&ma->syncp, start)); + start = u64_stats_fetch_begin_irq(&stats->syncp); + counter = stats->usage_cntrs[i]; + } while (u64_stats_fetch_retry_irq(&stats->syncp, + start)); masks_and_count[i].counter += counter; } diff --git a/net/openvswitch/flow_table.h b/net/openvswitch/flow_table.h index 6e7d4ac59353..43144396e192 100644 --- a/net/openvswitch/flow_table.h +++ b/net/openvswitch/flow_table.h @@ -38,12 +38,16 @@ struct mask_count { u64 counter; }; +struct mask_array_stats { + struct u64_stats_sync syncp; + u64 usage_cntrs[]; +}; + struct mask_array { struct rcu_head rcu; int count, max; - u64 __percpu *masks_usage_cntr; + struct mask_array_stats __percpu *masks_usage_stats; u64 *masks_usage_zero_cntr; - struct u64_stats_sync syncp; struct sw_flow_mask __rcu *masks[]; };