Re: [PATCH] mm/memcontrol.c: add memory allocation result check

[Michal Hocko]

On Mon 30-05-16 17:28:40, Wenwei Tao wrote:
> I think explicit BUG_ON may make the debug easier, since it can point
> out the wrong line.

Does it? NULL ptr dereferencec 6 lines below sounds pretty close to me.
I am not nacking this patch I just think it doesn't add much. If others
think it will be useful I will not object.

> 2016-05-30 16:53 GMT+08:00 Michal Hocko <mhocko@xxxxxxxxxx>:
> > On Mon 30-05-16 16:45:51, Wenwei Tao wrote:
> >> From: Wenwei Tao <ww.tao0320@xxxxxxxxx>
> >>
> >> The mem_cgroup_tree_per_node allocation might fail,
> >> check that before continue the memcg init. Since it
> >> is in the init phase, trigger the panic if that failure
> >> happens.
> >
> > We would blow up in the very same function so what is the point of the
> > explicit BUG_ON?
> >
> >> Signed-off-by: Wenwei Tao <ww.tao0320@xxxxxxxxx>
> >> ---
> >>  mm/memcontrol.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index 925b431..6385c62 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -5712,6 +5712,7 @@ static int __init mem_cgroup_init(void)
> >>
> >>               rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL,
> >>                                   node_online(node) ? node : NUMA_NO_NODE);
> >> +             BUG_ON(!rtpn);
> >>
> >>               for (zone = 0; zone < MAX_NR_ZONES; zone++) {
> >>                       struct mem_cgroup_tree_per_zone *rtpz;
> >> --
> >> 1.8.3.1
> >>
> >>
> >> --
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> >
> > --
> > Michal Hocko
> > SUSE Labs
> 
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-- 
Michal Hocko
SUSE Labs