Display current tcp failcnt in kmem cgroup

This patch introduces kmem.tcp.failcnt file, living in the
kmem_cgroup filesystem. Following the pattern in the other
memcg resources, this files keeps a counter of how many times
allocation failed due to limits being hit in this cgroup.
The root cgroup will always show a failcnt of 0.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Reviewed-by: Hiroyouki Kamezawa <kamezawa.hiroyu@jp.fujitsu.com>
CC: David S. Miller <davem@davemloft.net>
CC: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 0 deletions

diff --git a/net/ipv4/tcp_memcontrol.c b/net/ipv4/tcp_memcontrol.c
index 9481f235803e..d438fba31ba8 100644
--- a/net/ipv4/tcp_memcontrol.c
+++ b/net/ipv4/tcp_memcontrol.c
@@ -9,6 +9,7 @@
 static u64 tcp_cgroup_read(struct cgroup *cont, struct cftype *cft);
 static int tcp_cgroup_write(struct cgroup *cont, struct cftype *cft,
                             const char *buffer);
+static int tcp_cgroup_reset(struct cgroup *cont, unsigned int event);
 
 static struct cftype tcp_files[] = {
         {
@@ -22,6 +23,12 @@ static struct cftype tcp_files[] = {
                 .read_u64 = tcp_cgroup_read,
                 .private = RES_USAGE,
         },
+        {
+                .name = "kmem.tcp.failcnt",
+                .private = RES_FAILCNT,
+                .trigger = tcp_cgroup_reset,
+                .read_u64 = tcp_cgroup_read,
+        },
 };
 
 static inline struct tcp_memcontrol *tcp_from_cgproto(struct cg_proto *cg_proto)
@@ -197,12 +204,36 @@ static u64 tcp_cgroup_read(struct cgroup *cont, struct cftype *cft)
         case RES_USAGE:
                 val = tcp_read_usage(memcg);
                 break;
+        case RES_FAILCNT:
+                val = tcp_read_stat(memcg, RES_FAILCNT, 0);
+                break;
         default:
                 BUG();
         }
         return val;
 }
 
+static int tcp_cgroup_reset(struct cgroup *cont, unsigned int event)
+{
+        struct mem_cgroup *memcg;
+        struct tcp_memcontrol *tcp;
+        struct cg_proto *cg_proto;
+
+        memcg = mem_cgroup_from_cont(cont);
+        cg_proto = tcp_prot.proto_cgroup(memcg);
+        if (!cg_proto)
+                return 0;
+        tcp = tcp_from_cgproto(cg_proto);
+
+        switch (event) {
+        case RES_FAILCNT:
+                res_counter_reset_failcnt(&tcp->tcp_memory_allocated);
+                break;
+        }
+
+        return 0;
+}
+
 unsigned long long tcp_max_memory(const struct mem_cgroup *memcg)
 {
         struct tcp_memcontrol *tcp;