linux-kernel - Re: [PATCH] mm: compact: fix zoneindex in compact

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Date:	Thu, 19 May 2016 19:45:34 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Chen Feng <puck.chen@...ilicon.com>, mhocko@...e.com,
	kirill.shutemov@...ux.intel.com, hannes@...xchg.org, tj@...nel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	suzhuangluan@...ilicon.com, dan.zhao@...ilicon.com,
	qijiwen@...ilicon.com, xuyiping@...ilicon.com,
	oliver.fu@...ilicon.com, puck.chen@...mail.com
Subject: Re: [PATCH] mm: compact: fix zoneindex in compact

On 19.5.2016 19:23, Hugh Dickins wrote:
> On Thu, 19 May 2016, Vlastimil Babka wrote:
>> On 05/19/2016 02:11 PM, Vlastimil Babka wrote:
>>> On 05/19/2016 01:58 PM, Chen Feng wrote:
>>>> While testing the kcompactd in my platform 3G MEM only DMA ZONE.
>>>> I found the kcompactd never wakeup. It seems the zoneindex
>>>> has already minus 1 before. So the traverse here should be <=.
>>>
>>> Ouch, thanks!
>>>
>>>> Signed-off-by: Chen Feng <puck.chen@...ilicon.com>
>>>
>>> Fixes: 0f87baf4f7fb ("mm: wake kcompactd before kswapd's short sleep")
>>
>> Bah, not that one.
>>
>> Fixes: accf62422b3a ("mm, kswapd: replace kswapd compaction with waking
>> up kcompactd")
>>
>>> Cc: stable@...r.kernel.org
>>> Acked-by: Vlastimil Babka <vbabka@...e.cz>
>>>
>>>> ---
>>>>  mm/compaction.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/mm/compaction.c b/mm/compaction.c
>>>> index 8fa2540..e5122d9 100644
>>>> --- a/mm/compaction.c
>>>> +++ b/mm/compaction.c
>>>> @@ -1742,7 +1742,7 @@ static bool kcompactd_node_suitable(pg_data_t *pgdat)
>>>>  	struct zone *zone;
>>>>  	enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx;
>>>>  
>>>> -	for (zoneid = 0; zoneid < classzone_idx; zoneid++) {
>>>> +	for (zoneid = 0; zoneid <= classzone_idx; zoneid++) {
>>>>  		zone = &pgdat->node_zones[zoneid];
>>>>  
>>>>  		if (!populated_zone(zone))
> 
> Ignorant question: kcompactd_do_work() just below has a similar loop:

You spelled "Important" wrong.

> should that one be saying "zoneid <= cc.classzone_idx" too?

Yes. Chen, can you send updated patch (also with the ack/cc/fixes tags I added?)

Thanks!

> Hugh
>