Re: [RESEND PATCH v7 02/10] mm: Non-pmd-mappable, large folios for folio_add_new_anon_rmap()

[David Hildenbrand <david@redhat.com>]

On 22.11.23 17:29, Ryan Roberts wrote:
> In preparation for supporting anonymous small-sized THP, improve
> folio_add_new_anon_rmap() to allow a non-pmd-mappable, large folio to be
> passed to it. In this case, all contained pages are accounted using the
> order-0 folio (or base page) scheme.
> 
> Reviewed-by: Yu Zhao <yuzhao@google.com>
> Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
>   mm/rmap.c | 28 ++++++++++++++++++++--------
>   1 file changed, 20 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 49e4d86a4f70..b086dc957b0c 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1305,32 +1305,44 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma,
>    * This means the inc-and-test can be bypassed.
>    * The folio does not have to be locked.
>    *
> - * If the folio is large, it is accounted as a THP.  As the folio
> + * If the folio is pmd-mappable, it is accounted as a THP.  As the folio
>    * is new, it's assumed to be mapped exclusively by a single process.
>    */
>   void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
>   		unsigned long address)
>   {
> -	int nr;
> +	int nr = folio_nr_pages(folio);
> 
> -	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
> +	VM_BUG_ON_VMA(address < vma->vm_start ||
> +			address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
>   	__folio_set_swapbacked(folio);
> +	__folio_set_anon(folio, vma, address, true);

Likely the changed order doesn't matter.

LGTM

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

-- 
Cheers,

David / dhildenb