Re: [PATCH v5 14/25] rmap: Add support for PUD sized mappings to rmap

[David Hildenbrand <david@redhat.com>]

On 07.01.25 04:42, Alistair Popple wrote:
> The rmap doesn't currently support adding a PUD mapping of a
> folio. This patch adds support for entire PUD mappings of folios,
> primarily to allow for more standard refcounting of device DAX
> folios. Currently DAX is the only user of this and it doesn't require
> support for partially mapped PUD-sized folios so we don't support for
> that for now.
> 
> Signed-off-by: Alistair Popple <apopple@nvidia.com>
> 
> ---
> 
> Changes for v5:
>   - Fixed accounting as suggested by David.
> 
> Changes for v4:
> 
>   - New for v4, split out rmap changes as suggested by David.
> ---
>   include/linux/rmap.h | 15 ++++++++++-
>   mm/rmap.c            | 65 ++++++++++++++++++++++++++++++++++++++++++---
>   2 files changed, 76 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> index 683a040..7043914 100644
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -192,6 +192,7 @@ typedef int __bitwise rmap_t;
>   enum rmap_level {
>   	RMAP_LEVEL_PTE = 0,
>   	RMAP_LEVEL_PMD,
> +	RMAP_LEVEL_PUD,
>   };
>   
>   static inline void __folio_rmap_sanity_checks(const struct folio *folio,
> @@ -228,6 +229,14 @@ static inline void __folio_rmap_sanity_checks(const struct folio *folio,
>   		VM_WARN_ON_FOLIO(folio_nr_pages(folio) != HPAGE_PMD_NR, folio);
>   		VM_WARN_ON_FOLIO(nr_pages != HPAGE_PMD_NR, folio);
>   		break;
> +	case RMAP_LEVEL_PUD:
> +		/*
> +		 * Assume that we are creating * a single "entire" mapping of the
> +		 * folio.

Misplaced " *", can likely be fixed up when applying.

Apart from that LGTM

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb