[PATCH v3 6/7] 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>
CC: David S. Miller <davem@xxxxxxxxxxxxx>
CC: Hiroyouki Kamezawa <kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
---
 Documentation/cgroups/memory.txt |    1 +
 include/linux/memcontrol.h       |   10 ++++
 mm/memcontrol.c                  |   89 +++++++++++++++++++++++++++++++++++---
 net/ipv4/sysctl_net_ipv4.c       |   20 ++++++++
 4 files changed, 113 insertions(+), 7 deletions(-)

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 6f1954a..1ffde3e 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.max_memory      # set/show hard limit for tcp buf memory
 
 1. History
 
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 6b8c0c0..2df6db8 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -416,6 +416,9 @@ int tcp_init_cgroup_fill(struct proto *prot, struct cgroup *cgrp,
 			 struct cgroup_subsys *ss);
 void tcp_destroy_cgroup(struct proto *prot, struct cgroup *cgrp,
 			struct cgroup_subsys *ss);
+
+unsigned long tcp_max_memory(struct mem_cgroup *cg);
+void tcp_prot_mem(struct mem_cgroup *cg, long val, int idx);
 #else
 /* memcontrol includes sockets.h, that includes memcontrol.h ... */
 static inline void memcg_sock_mem_alloc(struct mem_cgroup *mem,
@@ -441,6 +444,13 @@ static inline void sock_update_memcg(struct sock *sk)
 static inline void sock_release_memcg(struct sock *sk)
 {
 }
+static inline unsigned long tcp_max_memory(struct mem_cgroup *cg)
+{
+	return 0;
+}
+static inline void tcp_prot_mem(struct mem_cgroup *cg, 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 5e9b2c7..be5ab89 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -345,6 +345,7 @@ struct mem_cgroup {
 	spinlock_t pcp_counter_lock;
 
 	/* per-cgroup tcp memory pressure knobs */
+	int tcp_max_memory;
 	atomic_long_t tcp_memory_allocated;
 	struct percpu_counter tcp_sockets_allocated;
 	/* those two are read-mostly, leave them at the end */
@@ -352,6 +353,11 @@ struct mem_cgroup {
 	int tcp_memory_pressure;
 };
 
+static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
+{
+	return (mem == root_mem_cgroup);
+}
+
 static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
 /* Writing them here to avoid exposing memcg's inner layout */
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
@@ -466,6 +472,56 @@ struct percpu_counter *sockets_allocated_tcp(struct mem_cgroup *sg)
 	return &sg->tcp_sockets_allocated;
 }
 
+static int tcp_write_maxmem(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+	struct mem_cgroup *sg = mem_cgroup_from_cont(cgrp);
+	struct mem_cgroup *parent = parent_mem_cgroup(sg);
+	struct net *net = current->nsproxy->net_ns;
+	int i;
+
+	if (!cgroup_lock_live_group(cgrp))
+		return -ENODEV;
+
+	/*
+	 * We can't allow more memory than our parents. Since this
+	 * will be tested for all calls, by induction, there is no need
+	 * to test any parent other than our own
+	 * */
+	if (parent && (val > parent->tcp_max_memory))
+		val = parent->tcp_max_memory;
+
+	sg->tcp_max_memory = val;
+
+	for (i = 0; i < 3; i++)
+		sg->tcp_prot_mem[i]  = min_t(long, val,
+					     net->ipv4.sysctl_tcp_mem[i]);
+
+	cgroup_unlock();
+
+	return 0;
+}
+
+static u64 tcp_read_maxmem(struct cgroup *cgrp, struct cftype *cft)
+{
+	struct mem_cgroup *sg = mem_cgroup_from_cont(cgrp);
+	u64 ret;
+
+	if (!cgroup_lock_live_group(cgrp))
+		return -ENODEV;
+	ret = sg->tcp_max_memory;
+
+	cgroup_unlock();
+	return ret;
+}
+
+static struct cftype tcp_files[] = {
+	{
+		.name = "kmem.tcp.max_memory",
+		.write_u64 = tcp_write_maxmem,
+		.read_u64 = tcp_read_maxmem,
+	},
+};
+
 /*
  * For ipv6, we only need to fill in the function pointers (can't initialize
  * things twice). So keep it separated
@@ -487,8 +543,10 @@ int tcp_init_cgroup(struct proto *prot, struct cgroup *cgrp,
 		    struct cgroup_subsys *ss)
 {
 	struct mem_cgroup *cg = mem_cgroup_from_cont(cgrp);
+	struct mem_cgroup *parent = parent_mem_cgroup(cg);
 	unsigned long limit;
 	struct net *net = current->nsproxy->net_ns;
+	int ret = 0;
 
 	cg->tcp_memory_pressure = 0;
 	atomic_long_set(&cg->tcp_memory_allocated, 0);
@@ -497,12 +555,25 @@ int tcp_init_cgroup(struct proto *prot, struct cgroup *cgrp,
 	limit = nr_free_buffer_pages() / 8;
 	limit = max(limit, 128UL);
 
+	if (parent)
+		cg->tcp_max_memory = parent->tcp_max_memory;
+	else
+		cg->tcp_max_memory = limit * 2;
+
 	cg->tcp_prot_mem[0] = net->ipv4.sysctl_tcp_mem[0];
 	cg->tcp_prot_mem[1] = net->ipv4.sysctl_tcp_mem[1];
 	cg->tcp_prot_mem[2] = net->ipv4.sysctl_tcp_mem[2];
 
 	tcp_init_cgroup_fill(prot, cgrp, ss);
-	return 0;
+	/*
+	 * For non-root cgroup, we need to set up all tcp-related variables,
+	 * but to be consistent with the rest of kmem management, we don't
+	 * expose any of the controls
+	 */
+	if (!mem_cgroup_is_root(cg))
+		ret = cgroup_add_files(cgrp, ss, tcp_files,
+				       ARRAY_SIZE(tcp_files));
+	return ret;
 }
 EXPORT_SYMBOL(tcp_init_cgroup);
 
@@ -514,6 +585,16 @@ void tcp_destroy_cgroup(struct proto *prot, struct cgroup *cgrp,
 	percpu_counter_destroy(&cg->tcp_sockets_allocated);
 }
 EXPORT_SYMBOL(tcp_destroy_cgroup);
+
+unsigned long tcp_max_memory(struct mem_cgroup *cg)
+{
+	return cg->tcp_max_memory;
+}
+
+void tcp_prot_mem(struct mem_cgroup *cg, long val, int idx)
+{
+	cg->tcp_prot_mem[idx] = val;
+}
 #endif /* CONFIG_INET */
 #endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
 
@@ -1092,12 +1173,6 @@ 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;
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

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