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Subject: Re: [PATCH] mm: Reduce memory bloat with THP
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: linux-mm@kvack.org, steven.sistare@oracle.com,
        Andrew Morton <akpm@linux-foundation.org>,
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References: <1513301359-117568-1-git-send-email-nitin.m.gupta@oracle.com>
 <20171215100151.b7j66q7sg2wsrex3@node.shutemov.name>
From: Nitin Gupta <nitin.m.gupta@oracle.com>
Message-ID: <efad97ec-b28d-ef84-75ee-02ac0d3378f1@oracle.com>
Date: Fri, 15 Dec 2017 23:21:46 -0800
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On 12/15/17 2:01 AM, Kirill A. Shutemov wrote:
> On Thu, Dec 14, 2017 at 05:28:52PM -0800, Nitin Gupta wrote:
>> diff --git a/mm/madvise.c b/mm/madvise.c
>> index 751e97a..b2ec07b 100644
>> --- a/mm/madvise.c
>> +++ b/mm/madvise.c
>> @@ -508,6 +508,7 @@ static long madvise_dontneed_single_vma(struct vm_area_struct *vma,
>>  					unsigned long start, unsigned long end)
>>  {
>>  	zap_page_range(vma, start, end - start);
>> +	vma->space_efficient = true;
>>  	return 0;
>>  }
>>  
> 
> And this modifies vma without down_write(mmap_sem).
> 

I thought this function was always called with mmmap_sem write locked.
I will check again.

- Nitin