xfrm6_tunnel: RCU conversion

xfrm6_tunnels use one rwlock to protect their hash tables.

Plain and straightforward conversion to RCU locking to permit better SMP
performance.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 19 deletions

diff --git a/net/ipv6/xfrm6_tunnel.c b/net/ipv6/xfrm6_tunnel.c
index 81a95c00e503..438831d33593 100644
--- a/net/ipv6/xfrm6_tunnel.c
+++ b/net/ipv6/xfrm6_tunnel.c
@@ -23,7 +23,7 @@
  */
 #include <linux/module.h>
 #include <linux/xfrm.h>
-#include <linux/list.h>
+#include <linux/rculist.h>
 #include <net/ip.h>
 #include <net/xfrm.h>
 #include <net/ipv6.h>
@@ -36,14 +36,15 @@
  * per xfrm_address_t.
  */
 struct xfrm6_tunnel_spi {
-        struct hlist_node list_byaddr;
-        struct hlist_node list_byspi;
-        xfrm_address_t addr;
-        u32 spi;
-        atomic_t refcnt;
+        struct hlist_node       list_byaddr;
+        struct hlist_node       list_byspi;
+        xfrm_address_t          addr;
+        u32                     spi;
+        atomic_t                refcnt;
+        struct rcu_head         rcu_head;
 };
 
-static DEFINE_RWLOCK(xfrm6_tunnel_spi_lock);
+static DEFINE_SPINLOCK(xfrm6_tunnel_spi_lock);
 
 static u32 xfrm6_tunnel_spi;
 
@@ -107,6 +108,7 @@ static void xfrm6_tunnel_spi_fini(void)
                 if (!hlist_empty(&xfrm6_tunnel_spi_byspi[i]))
                         return;
         }
+        rcu_barrier();
         kmem_cache_destroy(xfrm6_tunnel_spi_kmem);
         xfrm6_tunnel_spi_kmem = NULL;
 }
@@ -116,7 +118,7 @@ static struct xfrm6_tunnel_spi *__xfrm6_tunnel_spi_lookup(xfrm_address_t *saddr)
         struct xfrm6_tunnel_spi *x6spi;
         struct hlist_node *pos;
 
-        hlist_for_each_entry(x6spi, pos,
+        hlist_for_each_entry_rcu(x6spi, pos,
                              &xfrm6_tunnel_spi_byaddr[xfrm6_tunnel_spi_hash_byaddr(saddr)],
                              list_byaddr) {
                 if (memcmp(&x6spi->addr, saddr, sizeof(x6spi->addr)) == 0)
@@ -131,10 +133,10 @@ __be32 xfrm6_tunnel_spi_lookup(xfrm_address_t *saddr)
         struct xfrm6_tunnel_spi *x6spi;
         u32 spi;
 
-        read_lock_bh(&xfrm6_tunnel_spi_lock);
+        rcu_read_lock_bh();
         x6spi = __xfrm6_tunnel_spi_lookup(saddr);
         spi = x6spi ? x6spi->spi : 0;
-        read_unlock_bh(&xfrm6_tunnel_spi_lock);
+        rcu_read_unlock_bh();
         return htonl(spi);
 }
 
@@ -185,14 +187,15 @@ alloc_spi:
         if (!x6spi)
                 goto out;
 
+        INIT_RCU_HEAD(&x6spi->rcu_head);
         memcpy(&x6spi->addr, saddr, sizeof(x6spi->addr));
         x6spi->spi = spi;
         atomic_set(&x6spi->refcnt, 1);
 
-        hlist_add_head(&x6spi->list_byspi, &xfrm6_tunnel_spi_byspi[index]);
+        hlist_add_head_rcu(&x6spi->list_byspi, &xfrm6_tunnel_spi_byspi[index]);
 
         index = xfrm6_tunnel_spi_hash_byaddr(saddr);
-        hlist_add_head(&x6spi->list_byaddr, &xfrm6_tunnel_spi_byaddr[index]);
+        hlist_add_head_rcu(&x6spi->list_byaddr, &xfrm6_tunnel_spi_byaddr[index]);
 out:
         return spi;
 }
@@ -202,26 +205,32 @@ __be32 xfrm6_tunnel_alloc_spi(xfrm_address_t *saddr)
         struct xfrm6_tunnel_spi *x6spi;
         u32 spi;
 
-        write_lock_bh(&xfrm6_tunnel_spi_lock);
+        spin_lock_bh(&xfrm6_tunnel_spi_lock);
         x6spi = __xfrm6_tunnel_spi_lookup(saddr);
         if (x6spi) {
                 atomic_inc(&x6spi->refcnt);
                 spi = x6spi->spi;
         } else
                 spi = __xfrm6_tunnel_alloc_spi(saddr);
-        write_unlock_bh(&xfrm6_tunnel_spi_lock);
+        spin_unlock_bh(&xfrm6_tunnel_spi_lock);
 
         return htonl(spi);
 }
 
 EXPORT_SYMBOL(xfrm6_tunnel_alloc_spi);
 
+static void x6spi_destroy_rcu(struct rcu_head *head)
+{
+        kmem_cache_free(xfrm6_tunnel_spi_kmem,
+                        container_of(head, struct xfrm6_tunnel_spi, rcu_head));
+}
+
 void xfrm6_tunnel_free_spi(xfrm_address_t *saddr)
 {
         struct xfrm6_tunnel_spi *x6spi;
         struct hlist_node *pos, *n;
 
-        write_lock_bh(&xfrm6_tunnel_spi_lock);
+        spin_lock_bh(&xfrm6_tunnel_spi_lock);
 
         hlist_for_each_entry_safe(x6spi, pos, n,
                                   &xfrm6_tunnel_spi_byaddr[xfrm6_tunnel_spi_hash_byaddr(saddr)],
@@ -229,14 +238,14 @@ void xfrm6_tunnel_free_spi(xfrm_address_t *saddr)
         {
                 if (memcmp(&x6spi->addr, saddr, sizeof(x6spi->addr)) == 0) {
                         if (atomic_dec_and_test(&x6spi->refcnt)) {
-                                hlist_del(&x6spi->list_byaddr);
-                                hlist_del(&x6spi->list_byspi);
-                                kmem_cache_free(xfrm6_tunnel_spi_kmem, x6spi);
+                                hlist_del_rcu(&x6spi->list_byaddr);
+                                hlist_del_rcu(&x6spi->list_byspi);
+                                call_rcu(&x6spi->rcu_head, x6spi_destroy_rcu);
                                 break;
                         }
                 }
         }
-        write_unlock_bh(&xfrm6_tunnel_spi_lock);
+        spin_unlock_bh(&xfrm6_tunnel_spi_lock);
 }
 
 EXPORT_SYMBOL(xfrm6_tunnel_free_spi);