Re: [RFC PATCH] mm: Enable khugepaged to operate on non-writable VMAs

[Dev Jain <dev.jain@arm.com>]

On 01/09/25 2:02 pm, David Hildenbrand wrote:
> On 01.09.25 09:48, Dev Jain wrote:
>>
>> @@ -19,7 +19,7 @@
>>       EM( SCAN_PTE_NON_PRESENT,    "pte_non_present")        \
>>       EM( SCAN_PTE_UFFD_WP,        "pte_uffd_wp")            \
>>       EM( SCAN_PTE_MAPPED_HUGEPAGE, "pte_mapped_hugepage")        \
>> -    EM( SCAN_PAGE_RO,        "no_writable_page")        \
>> +    EM( SCAN_PAGE_RO,        "no_writable_page") /* deprecated */    \
>>       EM( SCAN_LACK_REFERENCED_PAGE, "lack_referenced_page")        \
>>       EM( SCAN_PAGE_NULL,        "page_null")            \
>>       EM( SCAN_SCAN_ABORT,        "scan_aborted")            \
>> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
>> index 4ec324a4c1fe..5ef8482597a9 100644
>> --- a/mm/khugepaged.c
>> +++ b/mm/khugepaged.c
>> @@ -39,7 +39,7 @@ enum scan_result {
>>       SCAN_PTE_NON_PRESENT,
>>       SCAN_PTE_UFFD_WP,
>>       SCAN_PTE_MAPPED_HUGEPAGE,
>> -    SCAN_PAGE_RO,
>> +    SCAN_PAGE_RO,    /* deprecated */
>
> Why can't we remove that completely.

(I raised this query in the other mail but due to not snipping stuff in 
between,

it may have been glossed over)

I was wondering whether a userspace script could break which assumes 
scan_page_ro

metric is there? I played with tracing long time back so I don't remember.


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