[PATCH v7 6/8] tcp buffer limitation: per-cgroup limit

[Glauber Costa]

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

We have to make sure that none of the memory pressure thresholds
specified in the namespace are bigger than the current cgroup.

Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: David S. Miller <davem@xxxxxxxxxxxxx>
CC: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
 Documentation/cgroups/memory.txt |    1 +
 include/linux/memcontrol.h       |   10 +++++
 mm/memcontrol.c                  |   79 ++++++++++++++++++++++++++++++++++----
 net/ipv4/sysctl_net_ipv4.c       |   20 ++++++++++
 4 files changed, 102 insertions(+), 8 deletions(-)

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 0dafd70..e773bd7 100644
--- a/Documentation/cgroups/memory.txt
+++ b/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
 
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index a27dad9..e0ccec5 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -397,6 +397,9 @@ int tcp_init_cgroup(const struct proto *prot, struct cgroup *cgrp,
 		    struct cgroup_subsys *ss);
 void tcp_destroy_cgroup(const struct proto *prot, 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);
 #else
 /* memcontrol includes sockets.h, that includes memcontrol.h ... */
 static inline void memcg_sockets_allocated_dec(struct mem_cgroup *memcg,
@@ -413,6 +416,13 @@ static inline void sock_update_memcg(struct sock *sk)
 static inline void sock_release_memcg(struct sock *sk)
 {
 }
+static inline unsigned long long tcp_max_memory(const struct mem_cgroup *memcg)
+{
+	return -1ULL;
+}
+static inline void tcp_prot_mem(struct mem_cgroup *memcg, long val, int idx)
+{
+}
 #endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
 #endif /* CONFIG_INET */
 #endif /* _LINUX_MEMCONTROL_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f953b32..b696267 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -365,6 +365,7 @@ enum mem_type {
 	_MEMSWAP,
 	_OOM_TYPE,
 	_KMEM,
+	_KMEM_TCP,
 };
 
 #define MEMFILE_PRIVATE(x, val)	(((x) << 16) | (val))
@@ -385,6 +386,11 @@ enum mem_type {
 
 static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
 static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont);
+static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
+{
+	return (memcg == root_mem_cgroup);
+}
+
 /* Writing them here to avoid exposing memcg's inner layout */
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
 #ifdef CONFIG_INET
@@ -510,6 +516,35 @@ struct percpu_counter *sockets_allocated_tcp(const struct mem_cgroup *memcg)
 }
 EXPORT_SYMBOL(sockets_allocated_tcp);
 
+static void tcp_update_limit(struct mem_cgroup *memcg, u64 val)
+{
+	struct net *net = current->nsproxy->net_ns;
+	int i;
+
+	val >>= PAGE_SHIFT;
+
+	for (i = 0; i < 3; i++)
+		memcg->tcp.tcp_prot_mem[i]  = min_t(long, val,
+					     net->ipv4.sysctl_tcp_mem[i]);
+}
+
+static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
+			    const char *buffer);
+
+static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft);
+/*
+ * We need those things internally in pages, so don't reuse
+ * mem_cgroup_{read,write}
+ */
+static struct cftype tcp_files[] = {
+	{
+		.name = "kmem.tcp.limit_in_bytes",
+		.write_string = mem_cgroup_write,
+		.read_u64 = mem_cgroup_read,
+		.private = MEMFILE_PRIVATE(_KMEM_TCP, RES_LIMIT),
+	},
+};
+
 static void tcp_create_cgroup(struct mem_cgroup *cg, struct cgroup_subsys *ss)
 {
 	struct res_counter *parent_res_counter = NULL;
@@ -527,6 +562,7 @@ int tcp_init_cgroup(const struct proto *prot, struct cgroup *cgrp,
 		    struct cgroup_subsys *ss)
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+	struct mem_cgroup *parent = parent_mem_cgroup(memcg);
 	struct net *net = current->nsproxy->net_ns;
 	/*
 	 * We need to initialize it at populate, not create time.
@@ -537,7 +573,20 @@ int tcp_init_cgroup(const struct proto *prot, struct cgroup *cgrp,
 	memcg->tcp.tcp_prot_mem[1] = net->ipv4.sysctl_tcp_mem[1];
 	memcg->tcp.tcp_prot_mem[2] = net->ipv4.sysctl_tcp_mem[2];
 
-	return 0;
+	/* Let root cgroup unlimited. All others, respect parent's if needed */
+	if (parent && !parent->use_hierarchy) {
+		unsigned long limit;
+		int ret;
+		limit = nr_free_buffer_pages() / 8;
+		limit = max(limit, 128UL);
+		ret = res_counter_set_limit(&memcg->tcp.tcp_memory_allocated,
+					    limit * 2);
+		if (ret)
+			return ret;
+	}
+
+	return cgroup_add_files(cgrp, ss, tcp_files,
+				ARRAY_SIZE(tcp_files));
 }
 EXPORT_SYMBOL(tcp_init_cgroup);
 
@@ -549,7 +598,18 @@ void tcp_destroy_cgroup(const struct proto *prot, struct cgroup *cgrp,
 	percpu_counter_destroy(&memcg->tcp.tcp_sockets_allocated);
 }
 EXPORT_SYMBOL(tcp_destroy_cgroup);
+
+unsigned long long tcp_max_memory(const struct mem_cgroup *memcg)
+{
+	return res_counter_read_u64(&CONSTCG(memcg)->tcp.tcp_memory_allocated,
+				    RES_LIMIT);
+}
 #undef CONSTCG
+
+void tcp_prot_mem(struct mem_cgroup *memcg, long val, int idx)
+{
+	memcg->tcp.tcp_prot_mem[idx] = val;
+}
 #endif /* CONFIG_INET */
 #endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
 
@@ -1048,12 +1108,6 @@ static struct mem_cgroup *mem_cgroup_get_next(struct mem_cgroup *iter,
 #define for_each_mem_cgroup_all(iter) \
 	for_each_mem_cgroup_tree_cond(iter, NULL, true)
 
-
-static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
-{
-	return (mem == root_mem_cgroup);
-}
-
 void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 {
 	struct mem_cgroup *mem;
@@ -4071,7 +4125,9 @@ static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
 	case _KMEM:
 		val = res_counter_read_u64(&mem->kmem, name);
 		break;
-
+	case _KMEM_TCP:
+		val = res_counter_read_u64(&mem->tcp.tcp_memory_allocated, name);
+		break;
 	default:
 		BUG();
 		break;
@@ -4104,6 +4160,13 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
 			break;
 		if (type == _MEM)
 			ret = mem_cgroup_resize_limit(memcg, val);
+#if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) && defined(CONFIG_INET)
+		else if (type == _KMEM_TCP) {
+			ret = res_counter_set_limit(&memcg->tcp.tcp_memory_allocated,
+						    val);
+			tcp_update_limit(memcg, val);
+		}
+#endif
 		else
 			ret = mem_cgroup_resize_memsw_limit(memcg, val);
 		break;
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index bbd67ab..cdc35f6 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -14,6 +14,7 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/nsproxy.h>
+#include <linux/memcontrol.h>
 #include <linux/swap.h>
 #include <net/snmp.h>
 #include <net/icmp.h>
@@ -182,6 +183,10 @@ 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
+	int i;
+	struct mem_cgroup *cg;
+#endif
 
 	ctl_table tmp = {
 		.data = &vec,
@@ -198,6 +203,21 @@ static int ipv4_tcp_mem(ctl_table *ctl, int write,
 	if (ret)
 		return ret;
 
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+	rcu_read_lock();
+	cg = mem_cgroup_from_task(current);
+	for (i = 0; i < 3; i++)
+		if (vec[i] > tcp_max_memory(cg)) {
+			rcu_read_unlock();
+			return -EINVAL;
+		}
+
+	tcp_prot_mem(cg, vec[0], 0);
+	tcp_prot_mem(cg, vec[1], 1);
+	tcp_prot_mem(cg, 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];
-- 
1.7.6.4

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