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ipvs: avoid rcu_barrier during netns cleanup 

commit 578bc3ef1e ("ipvs: reorganize dest trash") added
rcu_barrier() on cleanup to wait dest users and schedulers
like LBLC and LBLCR to put their last dest reference.
Using rcu_barrier with many namespaces is problematic.

Trying to fix it by freeing dest with kfree_rcu is not
a solution, RCU callbacks can run in parallel and execution
order is random.

Fix it by creating new function ip_vs_dest_put_and_free()
which is heavier than ip_vs_dest_put(). We will use it just
for schedulers like LBLC, LBLCR that can delay their dest
release.

By default, dests reference is above 0 if they are present in
service and it is 0 when deleted but still in trash list.
Change the dest trash code to use ip_vs_dest_put_and_free(),
so that refcnt -1 can be used for freeing. As result,
such checks remain in slow path and the rcu_barrier() from
netns cleanup can be removed.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
This commit is contained in:
Julian Anastasov 2013-10-09 09:24:27 +03:00 committed by Simon Horman
parent 120c9794a3
commit 9e4e948a3e
4 changed files with 9 additions and 7 deletions
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6
include/net/ip_vs.h
View File

@ -1442,6 +1442,12 @@ static inline void ip_vs_dest_put(struct ip_vs_dest *dest)
atomic_dec(&dest->refcnt);
}
static inline void ip_vs_dest_put_and_free(struct ip_vs_dest *dest)
{
if (atomic_dec_return(&dest->refcnt) < 0)
kfree(dest);
}
/*
* IPVS sync daemon data and function prototypes
* (from ip_vs_sync.c)

6
net/netfilter/ipvs/ip_vs_ctl.c
View File

@ -704,7 +704,7 @@ static void ip_vs_dest_free(struct ip_vs_dest *dest)
__ip_vs_dst_cache_reset(dest);
__ip_vs_svc_put(svc, false);
free_percpu(dest->stats.cpustats);
kfree(dest);
ip_vs_dest_put_and_free(dest);
}
/*
@ -3820,10 +3820,6 @@ void __net_exit ip_vs_control_net_cleanup(struct net *net)
{
struct netns_ipvs *ipvs = net_ipvs(net);
/* Some dest can be in grace period even before cleanup, we have to
* defer ip_vs_trash_cleanup until ip_vs_dest_wait_readers is called.
*/
rcu_barrier();
ip_vs_trash_cleanup(net);
ip_vs_stop_estimator(net, &ipvs->tot_stats);
ip_vs_control_net_cleanup_sysctl(net);

2
net/netfilter/ipvs/ip_vs_lblc.c
View File

@ -136,7 +136,7 @@ static void ip_vs_lblc_rcu_free(struct rcu_head *head)
struct ip_vs_lblc_entry,
rcu_head);
ip_vs_dest_put(en->dest);
ip_vs_dest_put_and_free(en->dest);
kfree(en);
}

2
net/netfilter/ipvs/ip_vs_lblcr.c
View File

@ -130,7 +130,7 @@ static void ip_vs_lblcr_elem_rcu_free(struct rcu_head *head)
struct ip_vs_dest_set_elem *e;
e = container_of(head, struct ip_vs_dest_set_elem, rcu_head);
ip_vs_dest_put(e->dest);
ip_vs_dest_put_and_free(e->dest);
kfree(e);
}