[CRIU] [PATCH 2/3] mem: if no parent image persists, can't rely on it

[Pavel Emelyanov]

On 04/09/2014 01:34 PM, Tikhomirov Pavel wrote:
> here was bug cause if e.g.: iterative snapshots are made and
> between two of them new process in process tree was created,
> criu will assume that all pages of this new process are "clean"
> believing that there is previous image for it and dirty tracking
> is on, but non of that is true, and it will end up in fail on restore.
>     
> also this bug was not catched because of error in zdtm, look 3/3
> 
> Signed-off-by: Tikhomirov Pavel <snorcht at gmail.com>
> ---
>  mem.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mem.c b/mem.c
> index ef1d010..6df198c 100644
> --- a/mem.c
> +++ b/mem.c
> @@ -106,7 +106,7 @@ static inline bool page_in_parent(u64 pme)
>   * the memory contents is present in the pagent image set.
>   */
>  
> -static int generate_iovs(struct vma_area *vma, struct page_pipe *pp, u64 *map, u64 *off)
> +static int generate_iovs(struct vma_area *vma, struct page_pipe *pp, u64 *map, u64 *off, bool no_parent)
>  {
>  	u64 *at = &map[PAGE_PFN(*off)];
>  	unsigned long pfn, nr_to_scan;
> @@ -130,7 +130,7 @@ static int generate_iovs(struct vma_area *vma, struct page_pipe *pp, u64 *map, u
>  		 * page. The latter would be checked in page-xfer.
>  		 */
>  
> -		if (page_in_parent(at[pfn])) {
> +		if (page_in_parent(at[pfn]) && !no_parent) {

If xfer.parent == NULL then page_in_parent should never return true. Why is this happening?

>  			ret = page_pipe_add_hole(pp, vaddr);
>  			pages[0]++;
>  		} else {
> @@ -282,7 +282,7 @@ static int __parasite_dump_pages_seized(struct parasite_ctl *ctl,
>  		if (!map)
>  			goto out_xfer;
>  again:
> -		ret = generate_iovs(vma_area, pp, map, &off);
> +		ret = generate_iovs(vma_area, pp, map, &off, xfer.parent == NULL);
>  		if (ret == -EAGAIN) {
>  			BUG_ON(pp_ret);
>  
>