[Devel] [PATCH v5 2/8] socket: initial cgroup code.

[Glauber Costa]

We aim to control the amount of kernel memory pinned at any
time by tcp sockets. To lay the foundations for this work,
this patch adds a pointer to the kmem_cgroup to the socket
structure.

Signed-off-by: Glauber Costa <glommer at parallels.com>
Acked-by: Kirill A. Shutemov<kirill at shutemov.name>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujtsu.com>
CC: David S. Miller <davem at davemloft.net>
CC: Eric W. Biederman <ebiederm at xmission.com>
---
 include/linux/memcontrol.h |   15 +++++++++++++++
 include/net/sock.h         |    2 ++
 mm/memcontrol.c            |   36 ++++++++++++++++++++++++++++++++++++
 net/core/sock.c            |    3 +++
 4 files changed, 56 insertions(+), 0 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 343bd76..88aea1b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -376,5 +376,20 @@ mem_cgroup_print_bad_page(struct page *page)
 }
 #endif
 
+#ifdef CONFIG_INET
+struct sock;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+void sock_update_memcg(struct sock *sk);
+void sock_release_memcg(struct sock *sk);
+
+#else
+static inline void sock_update_memcg(struct sock *sk)
+{
+}
+static inline void sock_release_memcg(struct sock *sk)
+{
+}
+#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
+#endif /* CONFIG_INET */
 #endif /* _LINUX_MEMCONTROL_H */
 
diff --git a/include/net/sock.h b/include/net/sock.h
index 8e4062f..afe1467 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -228,6 +228,7 @@ struct sock_common {
   *	@sk_security: used by security modules
   *	@sk_mark: generic packet mark
   *	@sk_classid: this socket's cgroup classid
+  *	@sk_cgrp: this socket's kernel memory (kmem) cgroup
   *	@sk_write_pending: a write to stream socket waits to start
   *	@sk_state_change: callback to indicate change in the state of the sock
   *	@sk_data_ready: callback to indicate there is data to be processed
@@ -339,6 +340,7 @@ struct sock {
 #endif
 	__u32			sk_mark;
 	u32			sk_classid;
+	struct mem_cgroup	*sk_cgrp;
 	void			(*sk_state_change)(struct sock *sk);
 	void			(*sk_data_ready)(struct sock *sk, int bytes);
 	void			(*sk_write_space)(struct sock *sk);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0871e3f..b1dcba9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -296,6 +296,42 @@ struct mem_cgroup {
 	spinlock_t pcp_counter_lock;
 };
 
+/* Writing them here to avoid exposing memcg's inner layout */
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
+#ifdef CONFIG_INET
+#include <net/sock.h>
+
+void sock_update_memcg(struct sock *sk)
+{
+	/* right now a socket spends its whole life in the same cgroup */
+	if (sk->sk_cgrp) {
+		WARN_ON(1);
+		return;
+	}
+
+	rcu_read_lock();
+	sk->sk_cgrp = mem_cgroup_from_task(current);
+
+	/*
+	 * We don't need to protect against anything task-related, because
+	 * we are basically stuck with the sock pointer that won't change,
+	 * even if the task that originated the socket changes cgroups.
+	 *
+	 * What we do have to guarantee, is that the chain leading us to
+	 * the top level won't change under our noses. Incrementing the
+	 * reference count via cgroup_exclude_rmdir guarantees that.
+	 */
+	cgroup_exclude_rmdir(mem_cgroup_css(sk->sk_cgrp));
+	rcu_read_unlock();
+}
+
+void sock_release_memcg(struct sock *sk)
+{
+	cgroup_release_and_wakeup_rmdir(mem_cgroup_css(sk->sk_cgrp));
+}
+#endif /* CONFIG_INET */
+#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
+
 /* Stuffs for move charges at task migration. */
 /*
  * Types of charges to be moved. "move_charge_at_immitgrate" is treated as a
diff --git a/net/core/sock.c b/net/core/sock.c
index bc745d0..5426ba0 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -125,6 +125,7 @@
 #include <net/xfrm.h>
 #include <linux/ipsec.h>
 #include <net/cls_cgroup.h>
+#include <linux/memcontrol.h>
 
 #include <linux/filter.h>
 
@@ -1141,6 +1142,7 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
 		atomic_set(&sk->sk_wmem_alloc, 1);
 
 		sock_update_classid(sk);
+		sock_update_memcg(sk);
 	}
 
 	return sk;
@@ -1172,6 +1174,7 @@ static void __sk_free(struct sock *sk)
 		put_cred(sk->sk_peer_cred);
 	put_pid(sk->sk_peer_pid);
 	put_net(sock_net(sk));
+	sock_release_memcg(sk);
 	sk_prot_free(sk->sk_prot_creator, sk);
 }
 
-- 
1.7.6