[PATCH 12/15] ipvs: convert locks used in persistence engines

[Simon Horman <horms@xxxxxxxxxxxx>]

From: Julian Anastasov <ja@xxxxxx>

Allow the readers to use RCU lock and for
PE module registrations use global mutex instead of
spinlock. All PE modules need to use synchronize_rcu
in their module exit handler.

Signed-off-by: Julian Anastasov <ja@xxxxxx>
Signed-off by: Hans Schillstrom <hans@xxxxxxxxxxxxxxx>
Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
---
 net/netfilter/ipvs/ip_vs_pe.c     |   43 +++++++++++--------------------------
 net/netfilter/ipvs/ip_vs_pe_sip.c |    1 +
 2 files changed, 14 insertions(+), 30 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_pe.c b/net/netfilter/ipvs/ip_vs_pe.c
index 5cf859c..5d9774c 100644
--- a/net/netfilter/ipvs/ip_vs_pe.c
+++ b/net/netfilter/ipvs/ip_vs_pe.c
@@ -13,8 +13,8 @@
 /* IPVS pe list */
 static LIST_HEAD(ip_vs_pe);
 
-/* lock for service table */
-static DEFINE_SPINLOCK(ip_vs_pe_lock);
+/* semaphore for IPVS PEs. */
+static DEFINE_MUTEX(ip_vs_pe_mutex);
 
 /* Bind a service with a pe */
 void ip_vs_bind_pe(struct ip_vs_service *svc, struct ip_vs_pe *pe)
@@ -36,9 +36,8 @@ struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
        IP_VS_DBG(10, "%s(): pe_name \"%s\"\n", __func__,
                  pe_name);
 
-       spin_lock_bh(&ip_vs_pe_lock);
-
-       list_for_each_entry(pe, &ip_vs_pe, n_list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(pe, &ip_vs_pe, n_list) {
                /* Test and get the modules atomically */
                if (pe->module &&
                    !try_module_get(pe->module)) {
@@ -47,14 +46,14 @@ struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
                }
                if (strcmp(pe_name, pe->name)==0) {
                        /* HIT */
-                       spin_unlock_bh(&ip_vs_pe_lock);
+                       rcu_read_unlock();
                        return pe;
                }
                if (pe->module)
                        module_put(pe->module);
        }
+       rcu_read_unlock();
 
-       spin_unlock_bh(&ip_vs_pe_lock);
        return NULL;
 }
 
@@ -83,22 +82,13 @@ int register_ip_vs_pe(struct ip_vs_pe *pe)
        /* increase the module use count */
        ip_vs_use_count_inc();
 
-       spin_lock_bh(&ip_vs_pe_lock);
-
-       if (!list_empty(&pe->n_list)) {
-               spin_unlock_bh(&ip_vs_pe_lock);
-               ip_vs_use_count_dec();
-               pr_err("%s(): [%s] pe already linked\n",
-                      __func__, pe->name);
-               return -EINVAL;
-       }
-
+       mutex_lock(&ip_vs_pe_mutex);
        /* Make sure that the pe with this name doesn't exist
         * in the pe list.
         */
        list_for_each_entry(tmp, &ip_vs_pe, n_list) {
                if (strcmp(tmp->name, pe->name) == 0) {
-                       spin_unlock_bh(&ip_vs_pe_lock);
+                       mutex_unlock(&ip_vs_pe_mutex);
                        ip_vs_use_count_dec();
                        pr_err("%s(): [%s] pe already existed "
                               "in the system\n", __func__, pe->name);
@@ -106,8 +96,8 @@ int register_ip_vs_pe(struct ip_vs_pe *pe)
                }
        }
        /* Add it into the d-linked pe list */
-       list_add(&pe->n_list, &ip_vs_pe);
-       spin_unlock_bh(&ip_vs_pe_lock);
+       list_add_rcu(&pe->n_list, &ip_vs_pe);
+       mutex_unlock(&ip_vs_pe_mutex);
 
        pr_info("[%s] pe registered.\n", pe->name);
 
@@ -118,17 +108,10 @@ EXPORT_SYMBOL_GPL(register_ip_vs_pe);
 /* Unregister a pe from the pe list */
 int unregister_ip_vs_pe(struct ip_vs_pe *pe)
 {
-       spin_lock_bh(&ip_vs_pe_lock);
-       if (list_empty(&pe->n_list)) {
-               spin_unlock_bh(&ip_vs_pe_lock);
-               pr_err("%s(): [%s] pe is not in the list. failed\n",
-                      __func__, pe->name);
-               return -EINVAL;
-       }
-
+       mutex_lock(&ip_vs_pe_mutex);
        /* Remove it from the d-linked pe list */
-       list_del(&pe->n_list);
-       spin_unlock_bh(&ip_vs_pe_lock);
+       list_del_rcu(&pe->n_list);
+       mutex_unlock(&ip_vs_pe_mutex);
 
        /* decrease the module use count */
        ip_vs_use_count_dec();
diff --git a/net/netfilter/ipvs/ip_vs_pe_sip.c 
b/net/netfilter/ipvs/ip_vs_pe_sip.c
index 12475ef..00cc024 100644
--- a/net/netfilter/ipvs/ip_vs_pe_sip.c
+++ b/net/netfilter/ipvs/ip_vs_pe_sip.c
@@ -172,6 +172,7 @@ static int __init ip_vs_sip_init(void)
 static void __exit ip_vs_sip_cleanup(void)
 {
        unregister_ip_vs_pe(&ip_vs_sip_pe);
+       synchronize_rcu();
 }
 
 module_init(ip_vs_sip_init);
-- 
1.7.10.4

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