Re: [PATCH v8 3/7] mm/highmem: introduce clear_user_highpages()

Ankur Arora
2025-11-10T07:21:37Z

David Hildenbrand (Red Hat) <david@kernel.org> writes:

> On 27.10.25 21:21, Ankur Arora wrote:
>> Define clear_user_highpages() which clears pages sequentially using
>> the single page variant.
>> With !CONFIG_HIGHMEM, pages are contiguous so use the range clearing
>> primitive clear_user_pages().
>> Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
>> Note: fixed
>
> That should be dropped.
>
>> ---
>> include/linux/highmem.h | 29 +++++++++++++++++++++++++++++
>> 1 file changed, 29 insertions(+)
>> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
>> index 105cc4c00cc3..c5f8b1556fd7 100644
>> --- a/include/linux/highmem.h
>> +++ b/include/linux/highmem.h
>> @@ -199,6 +199,11 @@ static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
>> /* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
>> #ifndef clear_user_highpage
>> +/**
>> + * clear_user_highpage() - clear a page to be mapped to user space
>> + * @page: start page
>> + * @vaddr: start address of the user mapping
>> + */
>> static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
>> {
>> void *addr = kmap_local_page(page);
>> @@ -207,6 +212,30 @@ static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
>> }
>> #endif
>> +/**
>> + * clear_user_highpages() - clear a page range to be mapped to user space
>> + * @page: start page
>> + * @vaddr: start address of the user mapping
>> + * @npages: number of pages
>> + *
>> + * Assumes that all the pages in the region (@page, +@npages) are valid
>> + * so this does no exception handling.
>> + */
>> +static inline void clear_user_highpages(struct page *page, unsigned long vaddr,
>> + unsigned int npages)
>> +{
>> + if (!IS_ENABLED(CONFIG_HIGHMEM)) {
>> + clear_user_pages(page_address(page), vaddr, page, npages);
>> + return;
>> + }
>> +
>> + do {
>> + clear_user_highpage(page, vaddr);
>> + vaddr += PAGE_SIZE;
>> + page++;
>> + } while (--npages);
>> +}
>> +
>> #ifndef vma_alloc_zeroed_movable_folio
>> /**
>> * vma_alloc_zeroed_movable_folio - Allocate a zeroed page for a VMA.
>
> Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>

Thanks (for this and the others.)

--
ankur