[Devel] [PATCH RHEL7 COMMIT] ms/ipv4: Don't do expensive useless work during inetdev destroy.

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.10.1.vz7.12.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.10.1.vz7.12.1
------>
commit 7cc3b754e77256e473e6294355f3883ff01da0af
Author: David Miller <davem at davemloft.net>
Date:   Tue Mar 15 19:54:43 2016 +0400

    ms/ipv4: Don't do expensive useless work during inetdev destroy.
    
    When an inetdev is destroyed, every address assigned to the interface
    is removed.  And in this scenerio we do two pointless things which can
    be very expensive if the number of assigned interfaces is large:
    
    1) Address promotion.  We are deleting all addresses, so there is no
       point in doing this.
    
    2) A full nf conntrack table purge for every address.  We only need to
       do this once, as is already caught by the existing
       masq_dev_notifier so masq_inet_event() can skip this.
    
    Reported-by: Solar Designer <solar at openwall.com>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    Tested-by: Cyrill Gorcunov <gorcunov at gmail.com>
    Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
    
    https://jira.sw.ru/browse/PSBM-42414
    
    The backport of net-next fbd40ea0180a2d328c5adc61414dc8bab9335ce2
    (http://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/patch/?id=fbd40ea0180a2d328c5adc61414dc8bab9335ce2)
---
 net/ipv4/devinet.c                          |  4 ++++
 net/ipv4/fib_frontend.c                     |  4 ++++
 net/ipv4/netfilter/nf_nat_masquerade_ipv4.c | 12 ++++++++++--
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 25ce9bd..8a69d4a 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -324,6 +324,9 @@ static void __inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
 
 	ASSERT_RTNL();
 
+	if (in_dev->dead)
+		goto no_promotions;
+
 	/* 1. Deleting primary ifaddr forces deletion all secondaries
 	 * unless alias promotion is set
 	 **/
@@ -370,6 +373,7 @@ static void __inet_del_ifa(struct in_device *in_dev, struct in_ifaddr **ifap,
 			fib_del_ifaddr(ifa, ifa1);
 	}
 
+no_promotions:
 	/* 2. Unlink it */
 
 	*ifap = ifa1->ifa_next;
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index a6d8553..bff0b97 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -814,6 +814,9 @@ void fib_del_ifaddr(struct in_ifaddr *ifa, struct in_ifaddr *iprim)
 		subnet = 1;
 	}
 
+	if (in_dev->dead)
+		goto no_promotions;
+
 	/* Deletion is more complicated than add.
 	 * We should take care of not to delete too much :-)
 	 *
@@ -889,6 +892,7 @@ void fib_del_ifaddr(struct in_ifaddr *ifa, struct in_ifaddr *iprim)
 		}
 	}
 
+no_promotions:
 	if (!(ok & BRD_OK))
 		fib_magic(RTM_DELROUTE, RTN_BROADCAST, ifa->ifa_broadcast, 32, prim);
 	if (subnet && ifa->ifa_prefixlen < 31) {
diff --git a/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c b/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c
index ab16e47..ee01003 100644
--- a/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c
+++ b/net/ipv4/netfilter/nf_nat_masquerade_ipv4.c
@@ -108,9 +108,17 @@ static int masq_inet_event(struct notifier_block *this,
 			   unsigned long event,
 			   void *ptr)
 {
-	struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
+	struct in_device *idev = ((struct in_ifaddr *)ptr)->ifa_dev;
 
-	return masq_device_event(this, event, dev);
+	/* The masq_dev_notifier will catch the case of the device going
+	 * down.  So if the inetdev is dead and being destroyed we have
+	 * no work to do.  Otherwise this is an individual address removal
+	 * and we have to perform the flush.
+	 */
+	if (idev->dead)
+		return NOTIFY_DONE;
+
+	return masq_device_event(this, event, idev->dev);
 }
 
 static struct notifier_block masq_dev_notifier = {