Re: [PATCH v3 0/2] __folio_split() clean up.

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

Hm something has gone weird in mm-new with this.

The patches are in the correct order, but the 2/2 patch, 'mm/huge_memory: use
folio_expected_ref_count() to calculate ref_count.' contains the cover letter
and has the suffix:

    This patch (of 2):

    Instead of open coding the ref_count calculation, use
    folio_expected_ref_count()

But immediately prior to it is 1/2 - mm/huge_memory: move unrelated code
out of __split_unmapped_folio() but with no cover letter reference.

Andrew - has quilt got confused here? :)

Thanks, Lorenzo

On Mon, Jul 14, 2025 at 01:18:21PM -0400, Zi Yan wrote:
> Based on the prior discussion[1], this patch improves
> __split_unmapped_folio() by making it reusable for splitting unmapped
> folios. This helps avoid the need for a new boolean unmapped parameter
> to guard mapping-related code.
>
> An additional benefit is that __split_unmapped_folio() could be
> called on after-split folios by __folio_split(). It can enable new split
> methods. For example, at deferred split time, unmapped subpages can
> scatter arbitrarily within a large folio, neither uniform nor non-uniform
> split can maximize after-split folio orders for mapped subpages.
> The hope is that by calling __split_unmapped_folio() multiple times,
> a better split result can be achieved.
>
> It passed mm selftests.
>
>
> Changelog
> ===
> From V2[3]:
> 1. Code format fixes
> 2. Restructured code to remove after_split goto label.
>
> From V1[2]:
> 1. Fixed indentations.
> 2. Used folio_expected_ref_count() to calculate ref_count instead of
>    open coding.
>
>
> [1] https://lore.kernel.org/linux-mm/94D8C1A4-780C-4BEC-A336-7D3613B54845@nvidia.com/
> [2] https://lore.kernel.org/linux-mm/20250711030259.3574392-1-ziy@nvidia.com/
> [2] https://lore.kernel.org/linux-mm/20250711182355.3592618-1-ziy@nvidia.com/
>
> Zi Yan (2):
>   mm/huge_memory: move unrelated code out of __split_unmapped_folio()
>   mm/huge_memory: use folio_expected_ref_count() to calculate ref_count.
>
>  mm/huge_memory.c | 289 +++++++++++++++++++++++------------------------
>  1 file changed, 142 insertions(+), 147 deletions(-)
>
> --
> 2.47.2
>