Re: [PATCH v5 3/3] kselftest: mm: introduce alloc_isolated_mem()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 9/10/26 13:22, Yeoreum Yun wrote:
> On Thu, Sep 10, 2026 at 01:14:42PM +0200, David Hildenbrand (Arm) wrote:
>> On 9/10/26 13:02, Yeoreum Yun wrote:
>>>
>>> Since there is no interface to get vm_flags not via /proc/self/smaps,
>>> It might be good to have it for preventing unwanted VMA merge.
>>>
>>> And might be useful for future to prevent unwated VMA merge.
>>
>> See my reply on why vm flags are generally not a problem. Just like other
>> properties that are not changed during VMA merging.
>>
>> Let's not perform random code changes without a clear picture.
>>
>> And just to emphasize again: VMA merging could already be a problem before
>> memalign() internal changes.
>>
>> (also observe here how we do a MADV_HUGEPAGE, so this is all rather arbitrary,
>> which is not good)
> 
> As I mentioned in my previous reply, what I’m trying to prevent here is
> a failure when checking, immediately after memory allocation,
> that a specific vm_flag is not set.
> 
> Yes, I agree that this could have been a problem even before
> the internal changes to memalign(). An unwanted VMA merge could already
> occur at the time of memory allocation.
> 
> So what I’m trying to avoid is a test failure where, due to such an
> unexpected VMA merge during allocation, the subsequent check that
> a specific vm_flag is not present fails.
Which is only a guard-region marker problem?

-- 
Cheers,

David