[PATCH net-next 02/19] ipvs: preparations for using rcu in schedulers

[Julian Anastasov <ja@xxxxxx>]

        Allow schedulers to use rcu_dereference when
returning destination on lookup. The RCU read-side critical
section will allow ip_vs_bind_dest to get dest refcnt as
preparation for the step where destinations will be
deleted without an IP_VS_WAIT_WHILE guard that holds the
packet processing during update.

        Add new optional scheduler methods add_dest,
del_dest and upd_dest. For now the methods are called
together with update_service but update_service will be
removed in a following change.

Signed-off-by: Julian Anastasov <ja@xxxxxx>
---
 include/net/ip_vs.h             |    6 ++++++
 net/netfilter/ipvs/ip_vs_core.c |    6 ++++++
 net/netfilter/ipvs/ip_vs_ctl.c  |    8 ++++++++
 3 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index 5ed8939..5af338b 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -805,6 +805,12 @@ struct ip_vs_scheduler {
        int (*done_service)(struct ip_vs_service *svc);
        /* scheduler updating service */
        int (*update_service)(struct ip_vs_service *svc);
+       /* dest is linked */
+       int (*add_dest)(struct ip_vs_service *svc, struct ip_vs_dest *dest);
+       /* dest is unlinked */
+       int (*del_dest)(struct ip_vs_service *svc, struct ip_vs_dest *dest);
+       /* dest is updated */
+       int (*upd_dest)(struct ip_vs_service *svc, struct ip_vs_dest *dest);
 
        /* selecting a server from the given service */
        struct ip_vs_dest* (*schedule)(struct ip_vs_service *svc,
diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index 207c3b9..7bf62d0 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -304,8 +304,10 @@ ip_vs_sched_persist(struct ip_vs_service *svc,
                 * template is not available.
                 * return *ignored=0 i.e. ICMP and NF_DROP
                 */
+               rcu_read_lock();
                dest = svc->scheduler->schedule(svc, skb);
                if (!dest) {
+                       rcu_read_unlock();
                        IP_VS_DBG(1, "p-schedule: no dest found.\n");
                        kfree(param.pe_data);
                        *ignored = 0;
@@ -321,6 +323,7 @@ ip_vs_sched_persist(struct ip_vs_service *svc,
                 * when the template expires */
                ct = ip_vs_conn_new(&param, &dest->addr, dport,
                                    IP_VS_CONN_F_TEMPLATE, dest, skb->mark);
+               rcu_read_unlock();
                if (ct == NULL) {
                        kfree(param.pe_data);
                        *ignored = -1;
@@ -449,8 +452,10 @@ ip_vs_schedule(struct ip_vs_service *svc, struct sk_buff 
*skb,
                return NULL;
        }
 
+       rcu_read_lock();
        dest = svc->scheduler->schedule(svc, skb);
        if (dest == NULL) {
+               rcu_read_unlock();
                IP_VS_DBG(1, "Schedule: no dest found.\n");
                return NULL;
        }
@@ -471,6 +476,7 @@ ip_vs_schedule(struct ip_vs_service *svc, struct sk_buff 
*skb,
                cp = ip_vs_conn_new(&p, &dest->addr,
                                    dest->port ? dest->port : pptr[1],
                                    flags, dest, skb->mark);
+               rcu_read_unlock();
                if (!cp) {
                        *ignored = -1;
                        return NULL;
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index a66b1c7..ae765b8 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -823,6 +823,11 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct 
ip_vs_dest *dest,
        if (add) {
                list_add(&dest->n_list, &svc->destinations);
                svc->num_dests++;
+               if (svc->scheduler->add_dest)
+                       svc->scheduler->add_dest(svc, dest);
+       } else {
+               if (svc->scheduler->upd_dest)
+                       svc->scheduler->upd_dest(svc, dest);
        }
 
        /* call the update_service, because server weight may be changed */
@@ -1069,6 +1074,9 @@ static void __ip_vs_unlink_dest(struct ip_vs_service *svc,
        list_del(&dest->n_list);
        svc->num_dests--;
 
+       if (svcupd && svc->scheduler->del_dest)
+               svc->scheduler->del_dest(svc, dest);
+
        /*
         *  Call the update_service function of its scheduler
         */
-- 
1.7.3.4

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