Re: [PATCH v4 2/8] socket: initial cgroup code.

[Glauber Costa]

On 10/03/2011 02:47 PM, Kirill A. Shutemov wrote:
> On Mon, Oct 03, 2011 at 02:18:37PM +0400, Glauber Costa wrote:
> > 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@xxxxxxxxxxxxx>
> > CC: David S. Miller<davem@xxxxxxxxxxxxx>
> > CC: Hiroyouki Kamezawa<kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > CC: Eric W. Biederman<ebiederm@xxxxxxxxxxxx>
> > ---
> >   include/linux/memcontrol.h |   15 +++++++++++++++
> >   include/net/sock.h         |    2 ++
> >   mm/memcontrol.c            |   33 +++++++++++++++++++++++++++++++++
> >   net/core/sock.c            |    3 +++
> >   4 files changed, 53 insertions(+), 0 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 3b535db..2cb9226 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -395,5 +395,20 @@ 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 8aaf4ce..08a520e 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -339,6 +339,39 @@ 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 */
> > +	BUG_ON(sk->sk_cgrp);
>
> Do we really want to panic in this case?
>
> What about WARN() + return?

Kirill,

I am keeping this code just to have something workable in between.
If you take a look at the last patch, this hunk is going away anyway.

So if you don't oppose it, I'll just keep it to avoid rebasing it.

> Otherwise: Acked-by: Kirill A. Shutemov<kirill@xxxxxxxxxxxxx>
>
> > +
> > +	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();
> > +}

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