Re: [PATCH 4/8] iov_iter: Convert iov_iter_extract_xarray_pages() to use folios

[David Hildenbrand <david@redhat.com>]

On 02.04.25 23:06, Matthew Wilcox (Oracle) wrote:
> ITER_XARRAY is exclusively used with xarrays that contain folios,
> not pages, so extract folio pointers from it, not page pointers.
> Removes a use of find_subpage().
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>   lib/iov_iter.c | 16 ++++++++--------
>   1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 7c50691fc5bb..a56bbf71a5d6 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1650,11 +1650,11 @@ static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i,
>   					     iov_iter_extraction_t extraction_flags,
>   					     size_t *offset0)
>   {
> -	struct page *page, **p;
> +	struct page **p;
> +	struct folio *folio;
>   	unsigned int nr = 0, offset;
>   	loff_t pos = i->xarray_start + i->iov_offset;
> -	pgoff_t index = pos >> PAGE_SHIFT;
> -	XA_STATE(xas, i->xarray, index);
> +	XA_STATE(xas, i->xarray, pos >> PAGE_SHIFT);
>   
>   	offset = pos & ~PAGE_MASK;
>   	*offset0 = offset;
> @@ -1665,17 +1665,17 @@ static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i,
>   	p = *pages;
>   
>   	rcu_read_lock();
> -	for (page = xas_load(&xas); page; page = xas_next(&xas)) {
> -		if (xas_retry(&xas, page))
> +	for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
> +		if (xas_retry(&xas, folio))
>   			continue;
>   
> -		/* Has the page moved or been split? */
> -		if (unlikely(page != xas_reload(&xas))) {
> +		/* Has the folio moved or been split? */
> +		if (unlikely(folio != xas_reload(&xas))) {
>   			xas_reset(&xas);
>   			continue;
>   		}
>   
> -		p[nr++] = find_subpage(page, xas.xa_index);
> +		p[nr++] = folio_file_page(folio, xas.xa_index);
>   		if (nr == maxpages)
>   			break;
>   	}

I'm curious, if we would have a large folio in there, and we'd want to 
extract multiple pages ... wouldn't we only extract one page per large 
folio only? :/

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

-- 
Cheers,

David / dhildenb