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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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