Re: [PATCH v9 1/3] madvise: use zap_page_range_single for madvise dontneed

[David Hildenbrand <david@redhat.com>]

On 12.11.22 00:26, Mike Kravetz wrote:
> Expose the routine zap_page_range_single to zap a range within a single
> vma.  The madvise routine madvise_dontneed_single_vma can use this
> routine as it explicitly operates on a single vma.  Also, update the mmu
> notification range in zap_page_range_single to take hugetlb pmd sharing
> into account.  This is required as MADV_DONTNEED supports hugetlb vmas.
> 
> Fixes: 90e7e7f5ef3f ("mm: enable MADV_DONTNEED for hugetlb mappings")
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> Reported-by: Wei Chen <harperchen1110@gmail.com>
> Cc: <stable@vger.kernel.org>


[...]

>   
> -/*
> - * Parameter block passed down to zap_pte_range in exceptional cases.
> - */
> -struct zap_details {
> -	struct folio *single_folio;	/* Locked folio to be unmapped */
> -	bool even_cows;			/* Zap COWed private pages too? */
> -	zap_flags_t zap_flags;		/* Extra flags for zapping */
> -};
> -
>   /* Whether we should zap all COWed (private) pages too */
>   static inline bool should_zap_cows(struct zap_details *details)
>   {
> @@ -1736,19 +1727,27 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
>    *
>    * The range must fit into one VMA.
>    */
> -static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
> +void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
>   		unsigned long size, struct zap_details *details)
>   {
> +	unsigned long end = address + size;

Could make that const.

>   	struct mmu_notifier_range range;
>   	struct mmu_gather tlb;
>   
>   	lru_add_drain();
>   	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
> -				address, address + size);
> +				address, end);
> +	if (is_vm_hugetlb_page(vma))
> +		adjust_range_if_pmd_sharing_possible(vma, &range.start,
> +						     &range.end);
>   	tlb_gather_mmu(&tlb, vma->vm_mm);
>   	update_hiwater_rss(vma->vm_mm);
>   	mmu_notifier_invalidate_range_start(&range);
> -	unmap_single_vma(&tlb, vma, address, range.end, details);
> +	/*
> +	 * unmap 'address-end' not 'range.start-range.end' as range
> +	 * could have been expanded for hugetlb pmd sharing.
> +	 */
> +	unmap_single_vma(&tlb, vma, address, end, details);
>   	mmu_notifier_invalidate_range_end(&range);
>   	tlb_finish_mmu(&tlb);
>   }


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

-- 
Thanks,

David / dhildenb