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    SubjectRe: [PATCH] memcg remove warning at DEBUG_VM=off
    On Wed, 8 Apr 2009 10:57:15 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

    > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-08 14:20:42]:
    >
    > > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > > This is against 2.6.30-rc1. (maybe no problem against mmotm.)
    > >
    > > ==
    > > Fix warning as
    > >
    > > CC mm/memcontrol.o
    > > mm/memcontrol.c:318: warning: ?$B!Fmem_cgroup_is_obsolete?$B!G defined but not used
    > >
    > > This is called only from VM_BUG_ON().
    > >
    > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > > ---
    > > Index: linux-2.6.30-rc1/mm/memcontrol.c
    > > ===================================================================
    > > --- linux-2.6.30-rc1.orig/mm/memcontrol.c
    > > +++ linux-2.6.30-rc1/mm/memcontrol.c
    > > @@ -314,13 +314,14 @@ static struct mem_cgroup *try_get_mem_cg
    > > return mem;
    > > }
    > >
    > > +#ifdef CONFIG_DEBUG_VM
    > > static bool mem_cgroup_is_obsolete(struct mem_cgroup *mem)
    > > {
    > > if (!mem)
    > > return true;
    > > return css_is_removed(&mem->css);
    > > }
    > > -
    > > +#endif
    >
    > Can we change the code to use
    >
    > VM_BUG_ON(!mem || css_is_removed(&mem->css));
    >

    yup.

    --- a/mm/memcontrol.c~memcg-remove-warning-when-config_debug_vm=n-fix
    +++ a/mm/memcontrol.c
    @@ -314,14 +314,13 @@ static struct mem_cgroup *try_get_mem_cg
    return mem;
    }

    -#ifdef CONFIG_DEBUG_VM
    static bool mem_cgroup_is_obsolete(struct mem_cgroup *mem)
    {
    if (!mem)
    return true;
    return css_is_removed(&mem->css);
    }
    -#endif
    +

    /*
    * Call callback function against all cgroup under hierarchy tree.
    @@ -933,7 +932,7 @@ static int __mem_cgroup_try_charge(struc
    if (unlikely(!mem))
    return 0;

    - VM_BUG_ON(mem_cgroup_is_obsolete(mem));
    + VM_BUG_ON(!mem || mem_cgroup_is_obsolete(mem));

    while (1) {
    int ret;
    _
    Although it really should be

    VM_BUG_ON(!mem);
    VM_BUG_ON(mem_cgroup_is_obsolete(mem));

    because if that BUG triggers, you'll be wondering which case caused it.




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