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From: Hangbin Liu <liuhangbin@gmail.com>
To: netdev@vger.kernel.org
Cc: Phil Karn <karn@ka9q.net>,
	Sukumar Gopalakrishnan <sukumarg1973@gmail.com>,
	"David S . Miller" <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	Hangbin Liu <liuhangbin@gmail.com>
Subject: [PATCHv2 net-next] ipmr: remove cache_resolve_queue_len
Date: Wed,  4 Sep 2019 11:34:08 +0800	[thread overview]
Message-ID: <20190904033408.13988-1-liuhangbin@gmail.com> (raw)
In-Reply-To: <20190903084359.13310-1-liuhangbin@gmail.com>

This is a re-post of previous patch wrote by David Miller[1].

Phil Karn reported[2] that on busy networks with lots of unresolved
multicast routing entries, the creation of new multicast group routes
can be extremely slow and unreliable.

The reason is we hard-coded multicast route entries with unresolved source
addresses(cache_resolve_queue_len) to 10. If some multicast route never
resolves and the unresolved source addresses increased, there will
be no ability to create new multicast route cache.

To resolve this issue, we need either add a sysctl entry to make the
cache_resolve_queue_len configurable, or just remove cache_resolve_queue_len
directly, as we already have the socket receive queue limits of mrouted
socket, pointed by David.

From my side, I'd perfer to remove the cache_resolve_queue_len instead
of creating two more(IPv4 and IPv6 version) sysctl entry.

[1] https://lkml.org/lkml/2018/7/22/11
[2] https://lkml.org/lkml/2018/7/21/343

v2: hold the mfc_unres_lock while walking the unresolved list in
queue_count(), as Nikolay Aleksandrov remind.

Reported-by: Phil Karn <karn@ka9q.net>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
---
 include/linux/mroute_base.h |  2 --
 net/ipv4/ipmr.c             | 30 +++++++++++++++++++++---------
 net/ipv6/ip6mr.c            | 10 +++-------
 3 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/include/linux/mroute_base.h b/include/linux/mroute_base.h
index 34de06b426ef..50fb89533029 100644
--- a/include/linux/mroute_base.h
+++ b/include/linux/mroute_base.h
@@ -235,7 +235,6 @@ struct mr_table_ops {
  * @mfc_hash: Hash table of all resolved routes for easy lookup
  * @mfc_cache_list: list of resovled routes for possible traversal
  * @maxvif: Identifier of highest value vif currently in use
- * @cache_resolve_queue_len: current size of unresolved queue
  * @mroute_do_assert: Whether to inform userspace on wrong ingress
  * @mroute_do_pim: Whether to receive IGMP PIMv1
  * @mroute_reg_vif_num: PIM-device vif index
@@ -252,7 +251,6 @@ struct mr_table {
 	struct rhltable		mfc_hash;
 	struct list_head	mfc_cache_list;
 	int			maxvif;
-	atomic_t		cache_resolve_queue_len;
 	bool			mroute_do_assert;
 	bool			mroute_do_pim;
 	bool			mroute_do_wrvifwhole;
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index c07bc82cbbe9..4d67c64d94a4 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -744,8 +744,6 @@ static void ipmr_destroy_unres(struct mr_table *mrt, struct mfc_cache *c)
 	struct sk_buff *skb;
 	struct nlmsgerr *e;
 
-	atomic_dec(&mrt->cache_resolve_queue_len);
-
 	while ((skb = skb_dequeue(&c->_c.mfc_un.unres.unresolved))) {
 		if (ip_hdr(skb)->version == 0) {
 			struct nlmsghdr *nlh = skb_pull(skb,
@@ -1133,9 +1131,11 @@ static int ipmr_cache_unresolved(struct mr_table *mrt, vifi_t vifi,
 	}
 
 	if (!found) {
+		bool was_empty;
+
 		/* Create a new entry if allowable */
-		if (atomic_read(&mrt->cache_resolve_queue_len) >= 10 ||
-		    (c = ipmr_cache_alloc_unres()) == NULL) {
+		c = ipmr_cache_alloc_unres();
+		if (!c) {
 			spin_unlock_bh(&mfc_unres_lock);
 
 			kfree_skb(skb);
@@ -1161,11 +1161,11 @@ static int ipmr_cache_unresolved(struct mr_table *mrt, vifi_t vifi,
 			return err;
 		}
 
-		atomic_inc(&mrt->cache_resolve_queue_len);
+		was_empty = list_empty(&mrt->mfc_unres_queue);
 		list_add(&c->_c.list, &mrt->mfc_unres_queue);
 		mroute_netlink_event(mrt, c, RTM_NEWROUTE);
 
-		if (atomic_read(&mrt->cache_resolve_queue_len) == 1)
+		if (was_empty)
 			mod_timer(&mrt->ipmr_expire_timer,
 				  c->_c.mfc_un.unres.expires);
 	}
@@ -1272,7 +1272,6 @@ static int ipmr_mfc_add(struct net *net, struct mr_table *mrt,
 		if (uc->mfc_origin == c->mfc_origin &&
 		    uc->mfc_mcastgrp == c->mfc_mcastgrp) {
 			list_del(&_uc->list);
-			atomic_dec(&mrt->cache_resolve_queue_len);
 			found = true;
 			break;
 		}
@@ -1328,7 +1327,7 @@ static void mroute_clean_tables(struct mr_table *mrt, int flags)
 	}
 
 	if (flags & MRT_FLUSH_MFC) {
-		if (atomic_read(&mrt->cache_resolve_queue_len) != 0) {
+		if (!list_empty(&mrt->mfc_unres_queue)) {
 			spin_lock_bh(&mfc_unres_lock);
 			list_for_each_entry_safe(c, tmp, &mrt->mfc_unres_queue, list) {
 				list_del(&c->list);
@@ -2750,9 +2749,22 @@ static int ipmr_rtm_route(struct sk_buff *skb, struct nlmsghdr *nlh,
 		return ipmr_mfc_delete(tbl, &mfcc, parent);
 }
 
+static int queue_count(struct mr_table *mrt)
+{
+	struct list_head *pos;
+	int count = 0;
+
+	spin_lock_bh(&mfc_unres_lock);
+	list_for_each(pos, &mrt->mfc_unres_queue)
+		count++;
+	spin_unlock_bh(&mfc_unres_lock);
+
+	return count;
+}
+
 static bool ipmr_fill_table(struct mr_table *mrt, struct sk_buff *skb)
 {
-	u32 queue_len = atomic_read(&mrt->cache_resolve_queue_len);
+	u32 queue_len = queue_count(mrt);
 
 	if (nla_put_u32(skb, IPMRA_TABLE_ID, mrt->id) ||
 	    nla_put_u32(skb, IPMRA_TABLE_CACHE_RES_QUEUE_LEN, queue_len) ||
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index e80d36c5073d..d02f0f903559 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -768,8 +768,6 @@ static void ip6mr_destroy_unres(struct mr_table *mrt, struct mfc6_cache *c)
 	struct net *net = read_pnet(&mrt->net);
 	struct sk_buff *skb;
 
-	atomic_dec(&mrt->cache_resolve_queue_len);
-
 	while ((skb = skb_dequeue(&c->_c.mfc_un.unres.unresolved)) != NULL) {
 		if (ipv6_hdr(skb)->version == 0) {
 			struct nlmsghdr *nlh = skb_pull(skb,
@@ -1148,8 +1146,8 @@ static int ip6mr_cache_unresolved(struct mr_table *mrt, mifi_t mifi,
 		 *	Create a new entry if allowable
 		 */
 
-		if (atomic_read(&mrt->cache_resolve_queue_len) >= 10 ||
-		    (c = ip6mr_cache_alloc_unres()) == NULL) {
+		c = ip6mr_cache_alloc_unres();
+		if (!c) {
 			spin_unlock_bh(&mfc_unres_lock);
 
 			kfree_skb(skb);
@@ -1176,7 +1174,6 @@ static int ip6mr_cache_unresolved(struct mr_table *mrt, mifi_t mifi,
 			return err;
 		}
 
-		atomic_inc(&mrt->cache_resolve_queue_len);
 		list_add(&c->_c.list, &mrt->mfc_unres_queue);
 		mr6_netlink_event(mrt, c, RTM_NEWROUTE);
 
@@ -1468,7 +1465,6 @@ static int ip6mr_mfc_add(struct net *net, struct mr_table *mrt,
 		if (ipv6_addr_equal(&uc->mf6c_origin, &c->mf6c_origin) &&
 		    ipv6_addr_equal(&uc->mf6c_mcastgrp, &c->mf6c_mcastgrp)) {
 			list_del(&_uc->list);
-			atomic_dec(&mrt->cache_resolve_queue_len);
 			found = true;
 			break;
 		}
@@ -1526,7 +1522,7 @@ static void mroute_clean_tables(struct mr_table *mrt, int flags)
 	}
 
 	if (flags & MRT6_FLUSH_MFC) {
-		if (atomic_read(&mrt->cache_resolve_queue_len) != 0) {
+		if (!list_empty(&mrt->mfc_unres_queue)) {
 			spin_lock_bh(&mfc_unres_lock);
 			list_for_each_entry_safe(c, tmp, &mrt->mfc_unres_queue, list) {
 				list_del(&c->list);
-- 
2.19.2


  parent reply	other threads:[~2019-09-04  3:34 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-03  8:43 [PATCH net] ipmr: remove cache_resolve_queue_len Hangbin Liu
2019-09-03  9:15 ` Nikolay Aleksandrov
2019-09-03 12:55   ` Hangbin Liu
2019-09-03 13:18     ` Nikolay Aleksandrov
2019-09-04  3:34 ` Hangbin Liu [this message]
2019-09-04  7:50   ` [PATCHv2 net-next] " Eric Dumazet
2019-09-05  3:37     ` Hangbin Liu
2019-09-06  7:36 ` [PATCHv3 net-next] ipmr: remove hard code cache_resolve_queue_len limit Hangbin Liu
2019-09-06 10:08   ` Nikolay Aleksandrov
2019-09-07 15:49   ` David Miller

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