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

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Message-ID: <d0163616-eacc-4ca2-9816-c577e710c5bd@arm.com>
Date: Mon, 21 Jul 2025 09:14:08 +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 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.

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