[CRIU] [PATCH] lazy-pages: use intermediate pipe in page_server_get_pages

[Andrei Vagin]

Pavel, could you review this patch.

On Mon, Jun 05, 2017 at 05:52:26PM +0300, Mike Rapoport wrote:
> Instead of splice()'ing pages directly from the page-pipe into the socket,
> use intermediate pipe and tee(). This way we keep the pages in page-pipe
> and they can be fetched again by the processes that were fork()'ed after
> restore.
> 
> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
> ---
>  criu/page-xfer.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/criu/page-xfer.c b/criu/page-xfer.c
> index c557407..6217d8a 100644
> --- a/criu/page-xfer.c
> +++ b/criu/page-xfer.c
> @@ -705,17 +705,19 @@ static int page_server_get_pages(int sk, struct page_server_iov *pi)
>  	if (!can_send_pages(ppb, iov, pi))
>  		return -1;
>  
> +	ret = tee(ppb->p[0], cxfer.p[1], iov->iov_len, 0);
> +	if (ret != iov->iov_len)
> +		return -1;
> +
>  	if (send_psi(sk, PS_IOV_ADD, pi->nr_pages, pi->vaddr, pi->dst_id))
>  		return -1;
>  
> -	ret = splice(ppb->p[0], NULL, sk, NULL, iov->iov_len, SPLICE_F_MOVE);
> +	ret = splice(cxfer.p[0], NULL, sk, NULL, iov->iov_len, SPLICE_F_MOVE);
>  	if (ret != iov->iov_len)
>  		return -1;
>  
>  	tcp_nodelay(sk, true);
>  
> -	page_pipe_destroy_ppb(ppb);
> -
>  	return 0;
>  }
>  
> @@ -724,6 +726,12 @@ static int page_server_serve(int sk)
>  	int ret = -1;
>  	bool flushed = false;
>  
> +	if (pipe(cxfer.p)) {
> +		pr_perror("Can't make pipe for xfer");
> +		close(sk);
> +		return -1;
> +	}
> +
>  	if (!opts.lazy_pages) {
>  		/*
>  		 * This socket only accepts data except one thing -- it
> @@ -731,19 +739,15 @@ static int page_server_serve(int sk)
>  		 * make it NODELAY all the time.
>  		 */
>  		tcp_nodelay(sk, true);
> -
> -		if (pipe(cxfer.p)) {
> -			pr_perror("Can't make pipe for xfer");
> -			close(sk);
> -			return -1;
> -		}
> -
> -		cxfer.pipe_size = fcntl(cxfer.p[0], F_GETPIPE_SZ, 0);
> -		pr_debug("Created xfer pipe size %u\n", cxfer.pipe_size);
>  	} else {
> +		if (fcntl(cxfer.p[0], F_SETPIPE_SZ, PIPE_MAX_SIZE * PAGE_SIZE) < 0)
> +			return -1;
>  		tcp_cork(sk, true);
>  	}
>  
> +	cxfer.pipe_size = fcntl(cxfer.p[0], F_GETPIPE_SZ, 0);
> +	pr_debug("Created xfer pipe size %u\n", cxfer.pipe_size);
> +
>  	while (1) {
>  		struct page_server_iov pi;
>  		u32 cmd;
> -- 
> 2.7.4
>