linux-kernel - Re: [PATCH] mm: init gfp mask in kcompactd_do

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Date:   Mon, 10 Oct 2016 16:16:39 +0800
From:   Xishi Qiu <qiuxishi@...wei.com>
To:     Vlastimil Babka <vbabka@...e.cz>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        "Michal Hocko" <mhocko@...e.com>, Minchan Kim <minchan@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Yisheng Xie <xieyisheng1@...wei.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: init gfp mask in kcompactd_do_work()

On 2016/10/10 14:40, Vlastimil Babka wrote:

> On 10/10/2016 05:35 AM, Xishi Qiu wrote:
>> We will use gfp_mask in the following path, but it's not init.
>>
>> kcompactd_do_work
>>     compact_zone
>>         gfpflags_to_migratetype
>>
>> However if not init, gfp_mask is always 0, and the result of
>> gfpflags_to_migratetype(0) and gfpflags_to_migratetype(GFP_KERNEL)
>> are the same, but it's a little confusion, so init it first.
> 
> Michal already did this as part of his patch, as it was needed to avoid wrongly restricting kcompactd to anonymous pages:
> 
> http://lkml.kernel.org/r/<20161007065019.GA18439@...p22.suse.cz>
> 

Oh yes, I missed your discussion.

Thanks,
Xishi Qiu

>> Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
>> ---
>>  mm/compaction.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index 9affb29..4b9a9d1 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -1895,10 +1895,10 @@ static void kcompactd_do_work(pg_data_t *pgdat)
>>      struct zone *zone;
>>      struct compact_control cc = {
>>          .order = pgdat->kcompactd_max_order,
>> +        .gfp_mask = GFP_KERNEL,
>>          .classzone_idx = pgdat->kcompactd_classzone_idx,
>>          .mode = MIGRATE_SYNC_LIGHT,
>>          .ignore_skip_hint = true,
>> -
>>      };
>>      bool success = false;
>>
>>
> 
> 
> .
>