From patchwork Thu Oct 15 17:09:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eelco Chaudron X-Patchwork-Id: 11839853 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 C9883C433E7 for ; Thu, 15 Oct 2020 17:09:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51AF022210 for ; Thu, 15 Oct 2020 17:09:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RnZidrLZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390059AbgJORJq (ORCPT ); Thu, 15 Oct 2020 13:09:46 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:49886 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389725AbgJORJp (ORCPT ); Thu, 15 Oct 2020 13:09:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602781783; 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=rOZn4VSKnJnp6C2TuuNsdspA2c0BFXEXOh0g4OMp0/E=; b=RnZidrLZaoJzuQyFBspKod7N6o3NmbAUj4G1gChLSRpCUqAyrBfT4Gyyf3mNJbNcLv1DaC kCW0JMAikyLqS1clczMWiltVeImMwc6/fiLnVsW1Wj3oW334SvwCkDMzuBGCFkgMcz5mbi 0jcIicOUikkHQVJk0fD72koqg3i1H44= 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-209-MfNI3l2iOsyY2r_Km_E8pw-1; Thu, 15 Oct 2020 13:09:40 -0400 X-MC-Unique: MfNI3l2iOsyY2r_Km_E8pw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 616E7AF9A0; Thu, 15 Oct 2020 17:09:38 +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 4B1EB75128; Thu, 15 Oct 2020 17:09:36 +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, i.maximets@ovn.org Subject: [PATCH net v3] net: openvswitch: fix to make sure flow_lookup() is not preempted Date: Thu, 15 Oct 2020 19:09:33 +0200 Message-Id: <160278168341.905188.913081997609088316.stgit@ebuild> User-Agent: StGit/0.21 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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 be called with BH disabled. However, this is fine in the general NAPI use case where the local BH is disabled. But, it's also called from the netlink context. The below patch makes sure that even in the netlink path, the BH is disabled. In addition, u64_stats_update_begin() requires a lock to ensure one writer which is not ensured here. Making it per-CPU and disabling NAPI (softirq) ensures that there is always only one writer. Fixes: eac87c413bf9 ("net: openvswitch: reorder masks array based on usage") Reported-by: Juri Lelli Signed-off-by: Eelco Chaudron --- v3: - Add comment to flow_lookup() call - Some update in code comments, and commit message v2: - Add u64_stats_update_begin() sync point protection - Moved patch to net from net-next branch net/openvswitch/flow_table.c | 58 +++++++++++++++++++++++++----------------- net/openvswitch/flow_table.h | 8 ++++-- 2 files changed, 41 insertions(+), 25 deletions(-) diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c index e2235849a57e..7d50c45fea37 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; } @@ -723,6 +724,8 @@ static struct sw_flow *masked_flow_lookup(struct table_instance *ti, /* Flow lookup does full lookup on flow table. It starts with * mask from index passed in *index. + * This function MUST be called with BH disabled due to the use + * of CPU specific variables. */ static struct sw_flow *flow_lookup(struct flow_table *tbl, struct table_instance *ti, @@ -732,7 +735,7 @@ 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 +745,9 @@ 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 +766,9 @@ 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 +854,17 @@ 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 BH 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 +1120,6 @@ 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 +1130,16 @@ 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[]; };