wireguard: allowedips: allocate nodes in kmem_cache

The previous commit moved from O(n) to O(1) for removal, but in the
process introduced an additional pointer member to a struct that
increased the size from 60 to 68 bytes, putting nodes in the 128-byte
slab. With deployed systems having as many as 2 million nodes, this
represents a significant doubling in memory usage (128 MiB -> 256 MiB).
Fix this by using our own kmem_cache, that's sized exactly right. This
also makes wireguard's memory usage more transparent in tools like
slabtop and /proc/slabinfo.

Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/wireguard/allowedips.c b/drivers/net/wireguard/allowedips.c
index 2785cfd..c540dce 100644 (file)
--- a/drivers/net/wireguard/allowedips.c
+++ b/drivers/net/wireguard/allowedips.c
@@ -6,6 +6,8 @@
 #include "allowedips.h"
 #include "peer.h"
 
+static struct kmem_cache *node_cache;
+
 static void swap_endian(u8 *dst, const u8 *src, u8 bits)
 {
        if (bits == 32) {
@@ -40,6 +42,11 @@ static void push_rcu(struct allowedips_node **stack,
        }
 }
 
+static void node_free_rcu(struct rcu_head *rcu)
+{
+       kmem_cache_free(node_cache, container_of(rcu, struct allowedips_node, rcu));
+}
+
 static void root_free_rcu(struct rcu_head *rcu)
 {
        struct allowedips_node *node, *stack[128] = {
@@ -49,7 +56,7 @@ static void root_free_rcu(struct rcu_head *rcu)
        while (len > 0 && (node = stack[--len])) {
                push_rcu(stack, node->bit[0], &len);
                push_rcu(stack, node->bit[1], &len);
-               kfree(node);
+               kmem_cache_free(node_cache, node);
        }
 }
 
@@ -164,7 +171,7 @@ static int add(struct allowedips_node __rcu **trie, u8 bits, const u8 *key,
                return -EINVAL;
 
        if (!rcu_access_pointer(*trie)) {
-               node = kzalloc(sizeof(*node), GFP_KERNEL);
+               node = kmem_cache_zalloc(node_cache, GFP_KERNEL);
                if (unlikely(!node))
                        return -ENOMEM;
                RCU_INIT_POINTER(node->peer, peer);
@@ -180,7 +187,7 @@ static int add(struct allowedips_node __rcu **trie, u8 bits, const u8 *key,
                return 0;
        }
 
-       newnode = kzalloc(sizeof(*newnode), GFP_KERNEL);
+       newnode = kmem_cache_zalloc(node_cache, GFP_KERNEL);
        if (unlikely(!newnode))
                return -ENOMEM;
        RCU_INIT_POINTER(newnode->peer, peer);
@@ -213,10 +220,10 @@ static int add(struct allowedips_node __rcu **trie, u8 bits, const u8 *key,
                return 0;
        }
 
-       node = kzalloc(sizeof(*node), GFP_KERNEL);
+       node = kmem_cache_zalloc(node_cache, GFP_KERNEL);
        if (unlikely(!node)) {
                list_del(&newnode->peer_list);
-               kfree(newnode);
+               kmem_cache_free(node_cache, newnode);
                return -ENOMEM;
        }
        INIT_LIST_HEAD(&node->peer_list);
@@ -306,7 +313,7 @@ void wg_allowedips_remove_by_peer(struct allowedips *table,
                if (child)
                        child->parent_bit = node->parent_bit;
                *rcu_dereference_protected(node->parent_bit, lockdep_is_held(lock)) = child;
-               kfree_rcu(node, rcu);
+               call_rcu(&node->rcu, node_free_rcu);
 
                /* TODO: Note that we currently don't walk up and down in order to
                 * free any potential filler nodes. This means that this function
@@ -350,4 +357,16 @@ struct wg_peer *wg_allowedips_lookup_src(struct allowedips *table,
        return NULL;
 }
 
+int __init wg_allowedips_slab_init(void)
+{
+       node_cache = KMEM_CACHE(allowedips_node, 0);
+       return node_cache ? 0 : -ENOMEM;
+}
+
+void wg_allowedips_slab_uninit(void)
+{
+       rcu_barrier();
+       kmem_cache_destroy(node_cache);
+}
+
 #include "selftest/allowedips.c"

diff --git a/drivers/net/wireguard/allowedips.h b/drivers/net/wireguard/allowedips.h
index f08f552..32d611a 100644 (file)
--- a/drivers/net/wireguard/allowedips.h
+++ b/drivers/net/wireguard/allowedips.h
@@ -19,7 +19,7 @@ struct allowedips_node {
        u8 bits[16] __aligned(__alignof(u64));
 
        /* Keep rarely used members at bottom to be beyond cache line. */
-       struct allowedips_node *__rcu *parent_bit; /* XXX: this puts us at 68->128 bytes instead of 60->64 bytes!! */
+       struct allowedips_node *__rcu *parent_bit;
        union {
                struct list_head peer_list;
                struct rcu_head rcu;
@@ -53,4 +53,7 @@ struct wg_peer *wg_allowedips_lookup_src(struct allowedips *table,
 bool wg_allowedips_selftest(void);
 #endif
 
+int wg_allowedips_slab_init(void);
+void wg_allowedips_slab_uninit(void);
+
 #endif /* _WG_ALLOWEDIPS_H */

diff --git a/drivers/net/wireguard/main.c b/drivers/net/wireguard/main.c
index 0a3ebfd..75dbe77 100644 (file)
--- a/drivers/net/wireguard/main.c
+++ b/drivers/net/wireguard/main.c
@@ -21,10 +21,15 @@ static int __init mod_init(void)
 {
        int ret;
 
+       ret = wg_allowedips_slab_init();
+       if (ret < 0)
+               goto err_allowedips;
+
 #ifdef DEBUG
+       ret = -ENOTRECOVERABLE;
        if (!wg_allowedips_selftest() || !wg_packet_counter_selftest() ||
            !wg_ratelimiter_selftest())
-               return -ENOTRECOVERABLE;
+               goto err_peer;
 #endif
        wg_noise_init();
 
@@ -50,6 +55,8 @@ err_netlink:
 err_device:
        wg_peer_uninit();
 err_peer:
+       wg_allowedips_slab_uninit();
+err_allowedips:
        return ret;
 }
 
@@ -58,6 +65,7 @@ static void __exit mod_exit(void)
        wg_genetlink_uninit();
        wg_device_uninit();
        wg_peer_uninit();
+       wg_allowedips_slab_uninit();
 }
 
 module_init(mod_init);