[CRIU] [RFC PATCH 07/16] criu: lazy_pages: use only IOV lists for bookkeeping

[Pavel Emelyanov]

On 09/27/2016 04:42 PM, Mike Rapoport wrote:
> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
> ---
>  criu/uffd.c | 84 ++++---------------------------------------------------------
>  1 file changed, 5 insertions(+), 79 deletions(-)
> 
> diff --git a/criu/uffd.c b/criu/uffd.c
> index 7f17d64..9a44807 100644
> --- a/criu/uffd.c
> +++ b/criu/uffd.c
> @@ -570,69 +570,6 @@ static int uffd_handle_page(struct lazy_pages_info *lpi, __u64 address,
>  	return rc;
>  }
>  
> -static int collect_uffd_pages(struct page_read *pr, struct lazy_pages_info *lpi)
> -{
> -	unsigned long base;
> -	int i;
> -	struct iovec iov;
> -	unsigned long nr_pages;
> -	unsigned long ps;
> -	int rc;
> -	struct uffd_pages_struct *uffd_pages;
> -	struct vma_area *vma;
> -	struct vm_area_list *vmas;
> -	struct pstree_item *item = pstree_item_by_virt(lpi->pid);
> -
> -	BUG_ON(!item);
> -
> -	vmas = &rsti(item)->vmas;
> -
> -	rc = pr->get_pagemap(pr, &iov);
> -	if (rc <= 0)
> -		return 0;
> -
> -	ps = page_size();
> -	nr_pages = iov.iov_len / ps;
> -	base = (unsigned long) iov.iov_base;
> -	pr_debug("iov.iov_base 0x%lx (%ld pages)\n", base, nr_pages);
> -
> -	for (i = 0; i < nr_pages; i++) {
> -		bool uffd_page = false;
> -		base = (unsigned long) iov.iov_base + (i * ps);
> -		/*
> -		 * Only pages which are MAP_ANONYMOUS and MAP_PRIVATE
> -		 * are relevant for userfaultfd handling.
> -		 * Loop over all VMAs to see if the flags matching.
> -		 */
> -		list_for_each_entry(vma, &vmas->h, list) {
> -			/*
> -			 * This loop assumes that base can actually be found
> -			 * in the VMA list.
> -			 */
> -			if (base >= vma->e->start && base < vma->e->end) {
> -				if (vma_entry_can_be_lazy(vma->e)) {
> -					uffd_page = true;
> -					break;
> -				}
> -			}
> -		}
> -
> -		/* This is not a page we are looking for. Move along */
> -		if (!uffd_page)
> -			continue;
> -
> -		pr_debug("Adding 0x%lx to our list\n", base);
> -
> -		uffd_pages = xzalloc(sizeof(struct uffd_pages_struct));
> -		if (!uffd_pages)
> -			return -1;
> -		uffd_pages->addr = base;
> -		list_add(&uffd_pages->list, &lpi->pages);
> -	}
> -
> -	return 1;
> -}
> -
>  static int handle_remaining_pages(struct lazy_pages_info *lpi, void *dest)
>  {
>  	struct lazy_iovec *lazy_iov;
> @@ -687,7 +624,6 @@ static int find_vmas(struct lazy_pages_info *lpi)
>  	struct vm_area_list vmas;
>  	int vn = 0;
>  	struct rst_info *ri;
> -	struct uffd_pages_struct *uffd_pages;
>  	struct pstree_item *item = pstree_item_by_virt(lpi->pid);
>  
>  	BUG_ON(!item);
> @@ -737,22 +673,12 @@ static int find_vmas(struct lazy_pages_info *lpi)
>  		ret = -1;
>  		goto out;
>  	}
> -	/*
> -	 * This puts all pages which should be handled by userfaultfd
> -	 * in the list uffd_list. This list is later used to detect if
> -	 * a page has already been transferred or if it needs to be
> -	 * pushed into the process using userfaultfd.
> -	 */
> -	do {
> -		ret = collect_uffd_pages(&lpi->pr, lpi);
> -		if (ret == -1) {
> -			goto out;
> -		}
> -	} while (ret);
>  
> -	/* Count detected pages */
> -	list_for_each_entry(uffd_pages, &lpi->pages, list)
> -	    ret++;
> +	ret = collect_lazy_iovecs(lpi);

Don't get this place. The collect_lazy_iovect() has already been called
on ud_open(), we do we need the 2nd call here?

> +	if (ret < 0) {
> +		pr_err("collect_lazy_iovecs=%d\n", ret);
> +		goto out;
> +	}
>  
>  	pr_debug("Found %d pages to be handled by UFFD\n", ret);
>  
>