Re: [memcg BUG] NULL pointer dereference wheng rmdir

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-19 18:33:41]:

> On Mon, 19 Jan 2009 17:15:05 +0800
> Li Zefan <lizf@cn.fujitsu.com> wrote:
> 
> > note: rmdir[11520] exited with preempt_count 1
> > ===========================================================================
> > 
> > 
> > And I've confirmed it's because (zone == NULL) in mem_cgroup_force_empty_list():
> > 
> > 
> Hmm, curious.  it will be
> 
> ==
> 	for_each_node_state(nid, N_POSSIBLE)
> 		for (zid = 0; zid < MAX_NR_ZONES; zid++)
> 			zone = &NODE_DATA(nid)->node_zones[zid];
> 
> ==
> 
> And, from this message,
> 
> Unable to handle kernel NULL pointer dereference (address 0000000000002680)
> 
> NODE_DATA(nid) seems to be NULL.
> 
> Hmm...could you try this ? Thank you for nice test, very helpful.
> -Kame
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> N_POSSIBLE doesn't means there is memory...and force_empty can
> visit invalud node which have no pgdat.
> 
> To visit all valid nodes, N_HIGH_MEMRY should be used.
> 
> Reporetd-by: Li Zefan <lizf@cn.fujitsu.com>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> ---
>  mm/memcontrol.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: mmotm-2.6.29-Jan16/mm/memcontrol.c
> ===================================================================
> --- mmotm-2.6.29-Jan16.orig/mm/memcontrol.c
> +++ mmotm-2.6.29-Jan16/mm/memcontrol.c
> @@ -1724,7 +1724,7 @@ move_account:
>  		/* This is for making all *used* pages to be on LRU. */
>  		lru_add_drain_all();
>  		ret = 0;
> -		for_each_node_state(node, N_POSSIBLE) {
> +		for_each_node_state(node, N_HIGH_MEMORY) {
>  			for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
>  				enum lru_list l;
>  				for_each_lru(l) {
> 
>

Looks correct to me, but I would wait for Li to test and confirm

Otherwise

Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
 

-- 
	Balbir

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