linux-kernel - Re: [PATCH] mm:mempolicy: skip VM_HUGETLB and VM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CA+eFSM0Nh4e0VjzDoaSEfbQNQwuHEnHkSmfsQCQmfgRUcOoofg@mail.gmail.com>
Date:	Tue, 19 Jan 2016 10:43:36 +0800
From:	Gavin Guo <gavin.guo@...onical.com>
To:	SeongJae Park <sj38.park@...il.com>
Cc:	Liang Chen <liangchen.linux@...il.com>, n-horiguchi@...jp.nec.com,
	linux-mm@...ck.org, riel@...hat.com, Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm:mempolicy: skip VM_HUGETLB and VM_MIXEDMAP VMA for
 lazy mbind

Hi SeongJae,

On Tue, Jan 19, 2016 at 9:12 AM, SeongJae Park <sj38.park@...il.com> wrote:
> Hello Liang,
>
> Just trivial comment below.
>
> On Mon, 18 Jan 2016, Liang Chen wrote:
>
>> VM_HUGETLB and VM_MIXEDMAP vma needs to be excluded to avoid compound
>> pages being marked for migration and unexpected COWs when handling
>> hugetlb fault.
>>
>> Thanks to Naoya Horiguchi for reminding me on these checks.
>>
>> Signed-off-by: Liang Chen <liangchen.linux@...il.com>
>> Signed-off-by: Gavin Guo <gavin.guo@...onical.com>
>> ---
>> mm/mempolicy.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> index 436ff411..415de70 100644
>> --- a/mm/mempolicy.c
>> +++ b/mm/mempolicy.c
>> @@ -610,8 +610,9 @@ static int queue_pages_test_walk(unsigned long start,
>> unsigned long end,
>>
>>         if (flags & MPOL_MF_LAZY) {
>>                 /* Similar to task_numa_work, skip inaccessible VMAs */
>> -               if (vma_migratable(vma) &&
>> -                       vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
>> +               if (vma_migratable(vma) && !is_vm_hugetlb_page(vma) &&
>> +                       (vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))
>> &&
>> +                       !(vma->vm_flags & VM_MIXEDMAP))
>
>
> Isn't there exists few unnecessary parenthesis? IMHO, it makes me hard to
> read the code.
>
> How about below code, instead?
>
> +             if (vma_migratable(vma) && !is_vm_hugetlb_page(vma) &&
> +                     vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE) &&

Thanks for your suggestion, it's good for the above. However, it should be
a typo for the following and I think you mean:

        ~vma->vm_flags & VM_MIXEDMAP

Even though the result is correct, I feel it's a bit of ambiguous for
people to understand and away from it's original meaning.

> +                     !vma->vm_flags & VM_MIXEDMAP)
>
>
> Thanks,
> SeongJae Park.
>
>>                         change_prot_numa(vma, start, endvma);
>>                 return 1;
>>         }
>> --
>> 1.9.1
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@...ck.org.  For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
>>
>