Re: [PATCH v4 2/7] mm/huge_memory: convert "tva_flags" to "enum tva_type"

[Zi Yan <ziy@nvidia.com>]

On 13 Aug 2025, at 9:55, Usama Arif wrote:

> From: David Hildenbrand <david@redhat.com>
>
> When determining which THP orders are eligible for a VMA mapping,
> we have previously specified tva_flags, however it turns out it is
> really not necessary to treat these as flags.
>
> Rather, we distinguish between distinct modes.
>
> The only case where we previously combined flags was with
> TVA_ENFORCE_SYSFS, but we can avoid this by observing that this
> is the default, except for MADV_COLLAPSE or an edge cases in
> collapse_pte_mapped_thp() and hugepage_vma_revalidate(), and
> adding a mode specifically for this case - TVA_FORCED_COLLAPSE.
>
> We have:
> * smaps handling for showing "THPeligible"
> * Pagefault handling
> * khugepaged handling
> * Forced collapse handling: primarily MADV_COLLAPSE, but also for
>   an edge case in collapse_pte_mapped_thp()
>
> Disregarding the edge cases, we only want to ignore sysfs settings only
> when we are forcing a collapse through MADV_COLLAPSE, otherwise we
> want to enforce it, hence this patch does the following flag to enum
> conversions:
>
> * TVA_SMAPS | TVA_ENFORCE_SYSFS -> TVA_SMAPS
> * TVA_IN_PF | TVA_ENFORCE_SYSFS -> TVA_PAGEFAULT
> * TVA_ENFORCE_SYSFS             -> TVA_KHUGEPAGED
> * 0                             -> TVA_FORCED_COLLAPSE
>
> With this change, we immediately know if we are in the forced collapse
> case, which will be valuable next.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> Acked-by: Usama Arif <usamaarif642@gmail.com>
> Signed-off-by: Usama Arif <usamaarif642@gmail.com>
> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> ---
>  fs/proc/task_mmu.c      |  4 ++--
>  include/linux/huge_mm.h | 30 ++++++++++++++++++------------
>  mm/huge_memory.c        |  8 ++++----
>  mm/khugepaged.c         | 17 ++++++++---------
>  mm/memory.c             | 14 ++++++--------
>  5 files changed, 38 insertions(+), 35 deletions(-)
>

Reviewed-by: Zi Yan <ziy@nvidia.com>

Best Regards,
Yan, Zi