[CRIU] [PATCH 3/3] criu: lazy-pages: use new pagemap features

[Pavel Emelyanov]

On 06/27/2016 07:53 AM, Mike Rapoport wrote:
> Pagemap now is more friendly to random accesses, enable use of new APIs.
> 
> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
> ---
>  criu/uffd.c | 29 +++++++++--------------------
>  1 file changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/criu/uffd.c b/criu/uffd.c
> index a920ae7..1e0a57a 100644
> --- a/criu/uffd.c
> +++ b/criu/uffd.c
> @@ -46,6 +46,8 @@ struct lazy_pages_info {
>  
>  	struct list_head pages;
>  
> +	struct page_read pr;
> +
>  	unsigned long total_pages;
>  	unsigned long copied_pages;
>  
> @@ -76,6 +78,8 @@ static void lpi_fini(struct lazy_pages_info *lpi)
>  {
>  	if (lpi->uffd)
>  		close(lpi->uffd);
> +	if (lpi->pr.close)
> +		lpi->pr.close(&lpi->pr);
>  	free(lpi);
>  }
>  
> @@ -326,34 +330,23 @@ out:
>  
>  static int get_page(struct lazy_pages_info *lpi, unsigned long addr, void *dest)
>  {
> -	struct iovec iov;
>  	int ret;
>  	unsigned char buf[PAGE_SIZE];
> -	struct page_read pr;
> -
> -	ret = open_page_read(lpi->pid, &pr, PR_TASK | PR_MOD);
> -	pr_debug("get_page ret %d\n", ret);
>  
> -	ret = pr.get_pagemap(&pr, &iov);
> -	pr_debug("get_pagemap ret %d\n", ret);
> -	if (ret <= 0)
> -		return ret;
> +	lpi->pr.reset(&lpi->pr);

Maybe it's better to reset the pr _only_ if the requesting address is below the 
recently read one?

>  
> -	ret = pr.seek_page(&pr, addr, true);
> +	ret = lpi->pr.seek_page(&lpi->pr, addr, true);
>  	pr_debug("seek_pagemap_page ret 0x%x\n", ret);
>  	if (ret <= 0)
>  		return ret;
>  
> -	ret = pr.read_pages(&pr, addr, 1, buf);
> +	ret = lpi->pr.read_pages(&lpi->pr, addr, 1, buf);
>  	pr_debug("read_pages ret %d\n", ret);
>  	if (ret <= 0)
>  		return ret;
>  
>  	memcpy(dest, buf, PAGE_SIZE);
>  
> -	if (pr.close)
> -		pr.close(&pr);
> -
>  	return 1;
>  }
>  
> @@ -560,7 +553,6 @@ static int find_vmas(struct lazy_pages_info *lpi)
>  	struct vm_area_list vmas;
>  	int vn = 0;
>  	struct rst_info *ri;
> -	struct page_read pr;
>  	struct uffd_pages_struct *uffd_pages;
>  	struct pstree_item *item = pstree_item_by_virt(lpi->pid);
>  
> @@ -606,7 +598,7 @@ static int find_vmas(struct lazy_pages_info *lpi)
>  		pr_info("vma 0x%"PRIx64" 0x%"PRIx64"\n", vma->e->start, vma->e->end);
>  	}
>  
> -	ret = open_page_read(lpi->pid, &pr, PR_TASK);
> +	ret = open_page_read(lpi->pid, &lpi->pr, PR_TASK);
>  	if (ret <= 0) {
>  		ret = -1;
>  		goto out;
> @@ -618,15 +610,12 @@ static int find_vmas(struct lazy_pages_info *lpi)
>  	 * pushed into the process using userfaultfd.
>  	 */
>  	do {
> -		ret = collect_uffd_pages(&pr, lpi);
> +		ret = collect_uffd_pages(&lpi->pr, lpi);
>  		if (ret == -1) {
>  			goto out;
>  		}
>  	} while (ret);
>  
> -	if (pr.close)
> -		pr.close(&pr);
> -
>  	/* Count detected pages */
>  	list_for_each_entry(uffd_pages, &lpi->pages, list)
>  	    ret++;
>