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    SubjectRe: [PATCH v5 6/8] tcp buffer limitation: per-cgroup limit
    On 10/04/2011 04:48 PM, Eric Dumazet wrote:
    > Le mardi 04 octobre 2011 à 16:17 +0400, Glauber Costa a écrit :
    >> 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@parallels.com>
    >> CC: David S. Miller<davem@davemloft.net>
    >> CC: Hiroyouki Kamezawa<kamezawa.hiroyu@jp.fujitsu.com>
    >> CC: Eric W. Biederman<ebiederm@xmission.com>
    >> ---
    >
    >
    >> --- 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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