Re: [RFC PATCH v3 1/4] filemap: add function filemap_map_folio_range()

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Fri, Feb 03, 2023 at 09:16:33PM +0800, Yin Fengwei wrote:
> @@ -3378,45 +3425,18 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
>  	addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
>  	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
>  	do {
> -again:
> -		page = folio_file_page(folio, xas.xa_index);
> -		if (PageHWPoison(page))
> -			goto unlock;
> -
> -		if (mmap_miss > 0)
> -			mmap_miss--;
> +		unsigned long end;
>  
>  		addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
>  		vmf->pte += xas.xa_index - last_pgoff;
>  		last_pgoff = xas.xa_index;
> +		end = folio->index + folio_nr_pages(folio) - 1;
> +		nr_pages = min(end, end_pgoff) - xas.xa_index + 1;
>  
> -		/*
> -		 * NOTE: If there're PTE markers, we'll leave them to be
> -		 * handled in the specific fault path, and it'll prohibit the
> -		 * fault-around logic.
> -		 */
> -		if (!pte_none(*vmf->pte))
> -			goto unlock;
> -
> -		/* We're about to handle the fault */
> -		if (vmf->address == addr)
> -			ret = VM_FAULT_NOPAGE;
> +		ret |=	filemap_map_folio_range(vmf, folio,
> +				xas.xa_index - folio->index, addr, nr_pages);
> +		xas.xa_index = end;

IIRC, end here can be beyond end_pgoff. Can it cause an issue? I don't see
it, but just in case.


-- 
  Kiryl Shutsemau / Kirill A. Shutemov