Re: [PATCH v5 6/8] tcp buffer limitation: per-cgroup limit

[Glauber Costa]

On 10/04/2011 04:48 PM, Eric Dumazet wrote:
> Le mardi 04 octobre 2011 Ã 16:17 +0400, Glauber Costa a Ãcrit :
> > 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>
> > ---
>
>
> > --- a/include/net/tcp.h
> > +++ b/include/net/tcp.h
> > @@ -256,6 +256,7 @@ extern int sysctl_tcp_thin_dupack;
> >   struct mem_cgroup;
> >   struct tcp_memcontrol {
> >   	/* 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 */
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>
> So tcp_max_memory is an "int".
>
>
> > +static u64 tcp_read_limit(struct cgroup *cgrp, struct cftype *cft)
> > +{
> > +	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
> > +	return memcg->tcp.tcp_max_memory<<  PAGE_SHIFT;
> > +}
>
> 1) Typical integer overflow here.
>
> You need :
>
> return ((u64)memcg->tcp.tcp_max_memory)<<  PAGE_SHIFT;

Thanks for spotting this, Eric.

> 2) Could you add const qualifiers when possible to your pointers ?

Well, I'll go over the patches again and see where I can add them.
Any specific place site you're concerned about?
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