linux-kernel - Re: [RFC PATCH 3/5] mm proc/task_mmu.c: add soft dirty pte checks for hugetlb

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Message-ID: <008f5ebc-6547-9244-24e0-710e3fe82b5e@oracle.com>
Date:   Thu, 18 Feb 2021 15:59:49 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, shu wang <malate_wangshu@...mail.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michel Lespinasse <walken@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 3/5] mm proc/task_mmu.c: add soft dirty pte checks for
 hugetlb

On 2/17/21 11:35 AM, Peter Xu wrote:
> On Wed, Feb 10, 2021 at 04:03:20PM -0800, Mike Kravetz wrote:
>> Pagemap was only using the vma flag PM_SOFT_DIRTY for hugetlb vmas.
>> This is insufficient.  Check the individual pte entries.
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
>> ---
>>  fs/proc/task_mmu.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>> index 602e3a52884d..829b35016aaa 100644
>> --- a/fs/proc/task_mmu.c
>> +++ b/fs/proc/task_mmu.c
>> @@ -1507,6 +1507,10 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
>>  		flags |= PM_SOFT_DIRTY;
>>  
>>  	pte = huge_ptep_get(ptep);
>> +
>> +	if (huge_pte_soft_dirty(pte))
>> +		flags |= PM_SOFT_DIRTY;
> 
> Should this be put into pte_present() chunk below?  Since I feel like we'd need
> huge_pte_swp_soft_dirty() for !pte_present().  Say, _PAGE_SOFT_DIRTY and
> _PAGE_SWP_SOFT_DIRTY can be different.
> 

Yes this should be moved below, and it should check for both.

Thanks,
-- 
Mike Kravetz

>> +
>>  	if (pte_present(pte)) {
>>  		struct page *page = pte_page(pte);
>>  
>> -- 
>> 2.29.2
>>
>