tcp buffer limitation: per-cgroup limit

This patch uses the "tcp.limit_in_bytes" field of the kmem_cgroup to
effectively control the amount of kernel memory pinned by a cgroup.

This value is ignored in the root cgroup, and in all others,
caps the value specified by the admin in the net namespaces'
view of tcp_sysctl_mem.

If namespaces are being used, the admin is allowed to set a
value bigger than cgroup's maximum, the same way it is allowed
to set pretty much unlimited values in a real box.

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>

Documentation/cgroups/memory.txt

@@ -78,6 +78,7 @@ Brief summary of control files.
 
  memory.independent_kmem_limit	 # select whether or not kernel memory limits are
 				   independent of user limits
+ memory.kmem.tcp.limit_in_bytes  # set/show hard limit for tcp buf memory
 
 1. History
 

include/net/tcp_memcontrol.h

@@ -14,4 +14,6 @@ struct tcp_memcontrol {
 struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg);
 int tcp_init_cgroup(struct cgroup *cgrp, struct cgroup_subsys *ss);
 void tcp_destroy_cgroup(struct cgroup *cgrp, struct cgroup_subsys *ss);
+unsigned long long tcp_max_memory(const struct mem_cgroup *memcg);
+void tcp_prot_mem(struct mem_cgroup *memcg, long val, int idx);
 #endif /* _TCP_MEMCG_H */

net/ipv4/sysctl_net_ipv4.c

@@ -24,6 +24,7 @@
 #include <net/cipso_ipv4.h>
 #include <net/inet_frag.h>
 #include <net/ping.h>
+#include <net/tcp_memcontrol.h>
 
 static int zero;
 static int tcp_retr1_max = 255;
@@ -182,6 +183,9 @@ static int ipv4_tcp_mem(ctl_table *ctl, int write,
 	int ret;
 	unsigned long vec[3];
 	struct net *net = current->nsproxy->net_ns;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+	struct mem_cgroup *memcg;
+#endif
 
 	ctl_table tmp = {
 		.data = &vec,
@@ -198,6 +202,16 @@ static int ipv4_tcp_mem(ctl_table *ctl, int write,
 	if (ret)
 		return ret;
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+	rcu_read_lock();
+	memcg = mem_cgroup_from_task(current);
+
+	tcp_prot_mem(memcg, vec[0], 0);
+	tcp_prot_mem(memcg, vec[1], 1);
+	tcp_prot_mem(memcg, vec[2], 2);
+	rcu_read_unlock();
+#endif
+
 	net->ipv4.sysctl_tcp_mem[0] = vec[0];
 	net->ipv4.sysctl_tcp_mem[1] = vec[1];
 	net->ipv4.sysctl_tcp_mem[2] = vec[2];

net/ipv4/tcp_memcontrol.c

@@ -6,6 +6,19 @@
 #include <linux/memcontrol.h>
 #include <linux/module.h>
 
+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 struct cftype tcp_files[] = {
+	{
+		.name = "kmem.tcp.limit_in_bytes",
+		.write_string = tcp_cgroup_write,
+		.read_u64 = tcp_cgroup_read,
+		.private = RES_LIMIT,
+	},
+};
+
 static inline struct tcp_memcontrol *tcp_from_cgproto(struct cg_proto *cg_proto)
 {
 	return container_of(cg_proto, struct tcp_memcontrol, cg_proto);
@@ -34,7 +47,7 @@ int tcp_init_cgroup(struct cgroup *cgrp, struct cgroup_subsys *ss)
 
 	cg_proto = tcp_prot.proto_cgroup(memcg);
 	if (!cg_proto)
-		return 0;
+		goto create_files;
 
 	tcp = tcp_from_cgproto(cg_proto);
 
@@ -57,7 +70,9 @@ int tcp_init_cgroup(struct cgroup *cgrp, struct cgroup_subsys *ss)
 	cg_proto->sockets_allocated = &tcp->tcp_sockets_allocated;
 	cg_proto->memcg = memcg;
 
-	return 0;
+create_files:
+	return cgroup_add_files(cgrp, ss, tcp_files,
+				ARRAY_SIZE(tcp_files));
 }
 EXPORT_SYMBOL(tcp_init_cgroup);
 
@@ -66,12 +81,130 @@ void tcp_destroy_cgroup(struct cgroup *cgrp, struct cgroup_subsys *ss)
 	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
 	struct cg_proto *cg_proto;
 	struct tcp_memcontrol *tcp;
+	u64 val;
 
 	cg_proto = tcp_prot.proto_cgroup(memcg);
 	if (!cg_proto)
 		return;
 
 	tcp = tcp_from_cgproto(cg_proto);
 	percpu_counter_destroy(&tcp->tcp_sockets_allocated);
+
+	val = res_counter_read_u64(&tcp->tcp_memory_allocated, RES_USAGE);
+
+	if (val != RESOURCE_MAX)
+		jump_label_dec(&memcg_socket_limit_enabled);
 }
 EXPORT_SYMBOL(tcp_destroy_cgroup);
+
+static int tcp_update_limit(struct mem_cgroup *memcg, u64 val)
+{
+	struct net *net = current->nsproxy->net_ns;
+	struct tcp_memcontrol *tcp;
+	struct cg_proto *cg_proto;
+	u64 old_lim;
+	int i;
+	int ret;
+
+	cg_proto = tcp_prot.proto_cgroup(memcg);
+	if (!cg_proto)
+		return -EINVAL;
+
+	if (val > RESOURCE_MAX)
+		val = RESOURCE_MAX;
+
+	tcp = tcp_from_cgproto(cg_proto);
+
+	old_lim = res_counter_read_u64(&tcp->tcp_memory_allocated, RES_LIMIT);
+	ret = res_counter_set_limit(&tcp->tcp_memory_allocated, val);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < 3; i++)
+		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)
+		jump_label_dec(&memcg_socket_limit_enabled);
+	else if (old_lim == RESOURCE_MAX && val != RESOURCE_MAX)
+		jump_label_inc(&memcg_socket_limit_enabled);
+
+	return 0;
+}
+
+static int tcp_cgroup_write(struct cgroup *cont, struct cftype *cft,
+			    const char *buffer)
+{
+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
+	unsigned long long val;
+	int ret = 0;
+
+	switch (cft->private) {
+	case RES_LIMIT:
+		/* see memcontrol.c */
+		ret = res_counter_memparse_write_strategy(buffer, &val);
+		if (ret)
+			break;
+		ret = tcp_update_limit(memcg, val);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	return ret;
+}
+
+static u64 tcp_read_stat(struct mem_cgroup *memcg, int type, u64 default_val)
+{
+	struct tcp_memcontrol *tcp;
+	struct cg_proto *cg_proto;
+
+	cg_proto = tcp_prot.proto_cgroup(memcg);
+	if (!cg_proto)
+		return default_val;
+
+	tcp = tcp_from_cgproto(cg_proto);
+	return res_counter_read_u64(&tcp->tcp_memory_allocated, type);
+}
+
+static u64 tcp_cgroup_read(struct cgroup *cont, struct cftype *cft)
+{
+	struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
+	u64 val;
+
+	switch (cft->private) {
+	case RES_LIMIT:
+		val = tcp_read_stat(memcg, RES_LIMIT, RESOURCE_MAX);
+		break;
+	default:
+		BUG();
+	}
+	return val;
+}
+
+unsigned long long tcp_max_memory(const struct mem_cgroup *memcg)
+{
+	struct tcp_memcontrol *tcp;
+	struct cg_proto *cg_proto;
+
+	cg_proto = tcp_prot.proto_cgroup((struct mem_cgroup *)memcg);
+	if (!cg_proto)
+		return 0;
+
+	tcp = tcp_from_cgproto(cg_proto);
+	return res_counter_read_u64(&tcp->tcp_memory_allocated, RES_LIMIT);
+}
+
+void tcp_prot_mem(struct mem_cgroup *memcg, long val, int idx)
+{
+	struct tcp_memcontrol *tcp;
+	struct cg_proto *cg_proto;
+
+	cg_proto = tcp_prot.proto_cgroup(memcg);
+	if (!cg_proto)
+		return;
+
+	tcp = tcp_from_cgproto(cg_proto);
+
+	tcp->tcp_prot_mem[idx] = val;
+}