linux-kernel - Re: [PATCH v5 1/7] mm: Refactor MM_CP_PROT

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Message-ID: <476c1978-af9a-4d25-8e5c-02f23de0b5b4@arm.com>
Date: Tue, 22 Jul 2025 16:35:54 +0530
From: Dev Jain <dev.jain@....com>
To: Barry Song <21cnbao@...il.com>
Cc: akpm@...ux-foundation.org, ryan.roberts@....com, david@...hat.com,
 willy@...radead.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 catalin.marinas@....com, will@...nel.org, Liam.Howlett@...cle.com,
 lorenzo.stoakes@...cle.com, vbabka@...e.cz, jannh@...gle.com,
 anshuman.khandual@....com, peterx@...hat.com, joey.gouly@....com,
 ioworker0@...il.com, kevin.brodsky@....com, quic_zhenhuah@...cinc.com,
 christophe.leroy@...roup.eu, yangyicong@...ilicon.com,
 linux-arm-kernel@...ts.infradead.org, hughd@...gle.com,
 yang@...amperecomputing.com, ziy@...dia.com
Subject: Re: [PATCH v5 1/7] mm: Refactor MM_CP_PROT_NUMA skipping case into
 new function


On 21/07/25 9:14 am, Dev Jain wrote:
>
> On 21/07/25 5:14 am, Barry Song wrote:
>> On Fri, Jul 18, 2025 at 5:03 PM Dev Jain <dev.jain@....com> wrote:
>>> Reduce indentation by refactoring the prot_numa case into a new 
>>> function.
>>> No functional change intended.
>>>
>>> Signed-off-by: Dev Jain <dev.jain@....com>
>> Reviewed-by: Barry Song <baohua@...nel.org>
>>
>>> ---
>>>   mm/mprotect.c | 101 
>>> +++++++++++++++++++++++++++-----------------------
>>>   1 file changed, 55 insertions(+), 46 deletions(-)
>>>
>>> diff --git a/mm/mprotect.c b/mm/mprotect.c
>>> index 88709c01177b..2a9c73bd0778 100644
>>> --- a/mm/mprotect.c
>>> +++ b/mm/mprotect.c
>>> @@ -83,6 +83,59 @@ bool can_change_pte_writable(struct 
>>> vm_area_struct *vma, unsigned long addr,
>>>          return pte_dirty(pte);
>>>   }
>>>
>>> +static bool prot_numa_skip(struct vm_area_struct *vma, unsigned 
>>> long addr,
>>> +                          pte_t oldpte, pte_t *pte, int target_node)
>>> +{
>> [...]
>>
>>> +       /*
>>> +        * Skip scanning top tier node if normal numa
>>> +        * balancing is disabled
>>> +        */
>>> +       if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && 
>>> toptier)
>>> +               return true;
>>> +
>>> +       if (folio_use_access_time(folio))
>>> +               folio_xchg_access_time(folio, 
>>> jiffies_to_msecs(jiffies));
>> Nit: I wonder if this should be moved elsewhere, since this isn't
>> actually about 'skipping', even though the function is named
>> `prot_numa_skip()`.
>
> Agreed, thanks. We can use prot_numa_skip() only to return true
> or false, and if returned false, we can call folio_xchg_access_time.
> I will wait for 2-3 days for any more comments and respin.

Since Andrew has already pulled this and we are quite late into the

release cycle, I'll do this cleanup in the next cycle.


>
>>
>>> +       return false;
>>> +}
>>> +
>> Thanks
>> Barry
>