Merge branch 'for-3.5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj...

[firefly-linux-kernel-4.4.55.git] / net / ipv4 / tcp_memcontrol.c

diff --git a/net/ipv4/tcp_memcontrol.c b/net/ipv4/tcp_memcontrol.c
index 151703791bb0d43818700349fb0a585736c7dc19..b6f3583ddfe83eae73370c9070c567e452518f57 100644 (file)
--- a/net/ipv4/tcp_memcontrol.c
+++ b/net/ipv4/tcp_memcontrol.c
@@ -74,9 +74,6 @@ void tcp_destroy_cgroup(struct mem_cgroup *memcg)
        percpu_counter_destroy(&tcp->tcp_sockets_allocated);
 
        val = res_counter_read_u64(&tcp->tcp_memory_allocated, RES_LIMIT);
-
-       if (val != RESOURCE_MAX)
-               static_key_slow_dec(&memcg_socket_limit_enabled);
 }
 EXPORT_SYMBOL(tcp_destroy_cgroup);
 
@@ -107,10 +104,33 @@ static int tcp_update_limit(struct mem_cgroup *memcg, u64 val)
                tcp->tcp_prot_mem[i] = min_t(long, val >> PAGE_SHIFT,
                                             net->ipv4.sysctl_tcp_mem[i]);
 
-       if (val == RESOURCE_MAX && old_lim != RESOURCE_MAX)
-               static_key_slow_dec(&memcg_socket_limit_enabled);
-       else if (old_lim == RESOURCE_MAX && val != RESOURCE_MAX)
-               static_key_slow_inc(&memcg_socket_limit_enabled);
+       if (val == RESOURCE_MAX)
+               clear_bit(MEMCG_SOCK_ACTIVE, &cg_proto->flags);
+       else if (val != RESOURCE_MAX) {
+               /*
+                * The active bit needs to be written after the static_key
+                * update. This is what guarantees that the socket activation
+                * function is the last one to run. See sock_update_memcg() for
+                * details, and note that we don't mark any socket as belonging
+                * to this memcg until that flag is up.
+                *
+                * We need to do this, because static_keys will span multiple
+                * sites, but we can't control their order. If we mark a socket
+                * as accounted, but the accounting functions are not patched in
+                * yet, we'll lose accounting.
+                *
+                * We never race with the readers in sock_update_memcg(),
+                * because when this value change, the code to process it is not
+                * patched in yet.
+                *
+                * The activated bit is used to guarantee that no two writers
+                * will do the update in the same memcg. Without that, we can't
+                * properly shutdown the static key.
+                */
+               if (!test_and_set_bit(MEMCG_SOCK_ACTIVATED, &cg_proto->flags))
+                       static_key_slow_inc(&memcg_socket_limit_enabled);
+               set_bit(MEMCG_SOCK_ACTIVE, &cg_proto->flags);
+       }
 
        return 0;
 }