Re: [RFC PATCH 5/5] filemap: batched update mm counter,rmap when map file folio

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

On Mon, Jan 30, 2023 at 08:55:04PM +0800, Yin Fengwei wrote:
> +++ b/mm/filemap.c
> @@ -3360,28 +3360,52 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
>  	struct vm_area_struct *vma = vmf->vma;
>  	struct file *file = vma->vm_file;
>  	unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
> -	int ref_count = 0, count = 0;
> +	int ref_count = 0, count = 0, maplen = 0;
> +	struct page *pg = page;

OK, having read it through, I think you're making your life a lot harder
by keeping page pointers at all.  I'd pass xas.xa_index - folio->index
from filemap_map_pages() as a parameter called something like 'first'.

>  	do {
> -		if (PageHWPoison(page))
> +		if (PageHWPoison(page)) {
> +			if (maplen) {
> +				page_add_file_rmap_range(folio, pg, maplen,
> +					vma, false);
> +				add_mm_counter(vma->vm_mm,
> +					mm_counter_file(pg), maplen);

Again you've made your life harder ;-)  Try something like this:

void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
{
	do_set_pte_range(vmf, page, addr, 1);
}

... and then here, you can do:

			if (maplen)
				do_set_pte_range(vmf, page - maplen - 1,
						base_addr, maplen);
			base_addr += (maplen + 1) * PAGE_SIZE
			maplen = 0;
			continue;