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>

diff --git a/net/ipv6/xfrm6_tunnel.c b/net/ipv6/xfrm6_tunnel.c
index 81a95c00e50355855cd7fdf22ac207b7e7dc1d91..438831d3359315718ff5cca2ca11ca01f878ae02 100644 (file)
--- 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);