From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1EBBC433F5 for ; Mon, 24 Jan 2022 12:09:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238171AbiAXMJW (ORCPT ); Mon, 24 Jan 2022 07:09:22 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:34480 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238134AbiAXMJV (ORCPT ); Mon, 24 Jan 2022 07:09:21 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id DC610B80EFA for ; Mon, 24 Jan 2022 12:09:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EBF26C340E1; Mon, 24 Jan 2022 12:09:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643026159; bh=v3kttT/BRwIbQp+8AV2QG1ExUjjtohhvXr67VoflewA=; h=Subject:To:Cc:From:Date:From; b=wbf+L3N4G43NUI+jwEYkRLRlUx4FekVdUFj3ycJI7eBa2PaQnxBo/pTRfqhLRWmBi MBLhuaeFKhQts7pik4WTvQJdkIwza/FACjMXtDNpMVrjrBDPfa2fo9/EbOnsGHr06H IRx1ozLUh+fL11iXF/ZLXWPT4IFwB6TLTxI7pHCE= Subject: FAILED: patch "[PATCH] ipv4: avoid quadratic behavior in netns dismantle" failed to apply to 4.4-stable tree To: edumazet@google.com, dsahern@kernel.org, kuba@kernel.org Cc: From: Date: Mon, 24 Jan 2022 13:09:16 +0100 Message-ID: <16430261561186@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d07418afea8f1d9896aaf9dc5ae47ac4f45b220c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 19 Jan 2022 02:04:12 -0800 Subject: [PATCH] ipv4: avoid quadratic behavior in netns dismantle net/ipv4/fib_semantics.c uses an hash table of 256 slots, keyed by device ifindexes: fib_info_devhash[DEVINDEX_HASHSIZE] Problem is that with network namespaces, devices tend to use the same ifindex. lo device for instance has a fixed ifindex of one, for all network namespaces. This means that hosts with thousands of netns spend a lot of time looking at some hash buckets with thousands of elements, notably at netns dismantle. Simply add a per netns perturbation (net_hash_mix()) to spread elements more uniformely. Also change fib_devindex_hashfn() to use more entropy. Fixes: aa79e66eee5d ("net: Make ifindex generation per-net namespace") Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Signed-off-by: Jakub Kicinski diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index 45619c005b8d..9813949da104 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -29,6 +29,7 @@ #include #include #include +#include #include #include @@ -319,11 +320,15 @@ static inline int nh_comp(struct fib_info *fi, struct fib_info *ofi) static inline unsigned int fib_devindex_hashfn(unsigned int val) { - unsigned int mask = DEVINDEX_HASHSIZE - 1; + return hash_32(val, DEVINDEX_HASHBITS); +} + +static struct hlist_head * +fib_info_devhash_bucket(const struct net_device *dev) +{ + u32 val = net_hash_mix(dev_net(dev)) ^ dev->ifindex; - return (val ^ - (val >> DEVINDEX_HASHBITS) ^ - (val >> (DEVINDEX_HASHBITS * 2))) & mask; + return &fib_info_devhash[fib_devindex_hashfn(val)]; } static unsigned int fib_info_hashfn_1(int init_val, u8 protocol, u8 scope, @@ -433,12 +438,11 @@ int ip_fib_check_default(__be32 gw, struct net_device *dev) { struct hlist_head *head; struct fib_nh *nh; - unsigned int hash; spin_lock(&fib_info_lock); - hash = fib_devindex_hashfn(dev->ifindex); - head = &fib_info_devhash[hash]; + head = fib_info_devhash_bucket(dev); + hlist_for_each_entry(nh, head, nh_hash) { if (nh->fib_nh_dev == dev && nh->fib_nh_gw4 == gw && @@ -1609,12 +1613,10 @@ struct fib_info *fib_create_info(struct fib_config *cfg, } else { change_nexthops(fi) { struct hlist_head *head; - unsigned int hash; if (!nexthop_nh->fib_nh_dev) continue; - hash = fib_devindex_hashfn(nexthop_nh->fib_nh_dev->ifindex); - head = &fib_info_devhash[hash]; + head = fib_info_devhash_bucket(nexthop_nh->fib_nh_dev); hlist_add_head(&nexthop_nh->nh_hash, head); } endfor_nexthops(fi) } @@ -1966,8 +1968,7 @@ void fib_nhc_update_mtu(struct fib_nh_common *nhc, u32 new, u32 orig) void fib_sync_mtu(struct net_device *dev, u32 orig_mtu) { - unsigned int hash = fib_devindex_hashfn(dev->ifindex); - struct hlist_head *head = &fib_info_devhash[hash]; + struct hlist_head *head = fib_info_devhash_bucket(dev); struct fib_nh *nh; hlist_for_each_entry(nh, head, nh_hash) { @@ -1986,12 +1987,11 @@ void fib_sync_mtu(struct net_device *dev, u32 orig_mtu) */ int fib_sync_down_dev(struct net_device *dev, unsigned long event, bool force) { - int ret = 0; - int scope = RT_SCOPE_NOWHERE; + struct hlist_head *head = fib_info_devhash_bucket(dev); struct fib_info *prev_fi = NULL; - unsigned int hash = fib_devindex_hashfn(dev->ifindex); - struct hlist_head *head = &fib_info_devhash[hash]; + int scope = RT_SCOPE_NOWHERE; struct fib_nh *nh; + int ret = 0; if (force) scope = -1; @@ -2136,7 +2136,6 @@ static void fib_select_default(const struct flowi4 *flp, struct fib_result *res) int fib_sync_up(struct net_device *dev, unsigned char nh_flags) { struct fib_info *prev_fi; - unsigned int hash; struct hlist_head *head; struct fib_nh *nh; int ret; @@ -2152,8 +2151,7 @@ int fib_sync_up(struct net_device *dev, unsigned char nh_flags) } prev_fi = NULL; - hash = fib_devindex_hashfn(dev->ifindex); - head = &fib_info_devhash[hash]; + head = fib_info_devhash_bucket(dev); ret = 0; hlist_for_each_entry(nh, head, nh_hash) {