[CRIU] [PATCH 1/5] page-server: Introduce page_server_start_sync_read

[Mike Rapoport]

On Wed, Jun 14, 2017 at 01:14:28PM +0300, Pavel Emelyanov wrote:
> There's no need in two API calls to read xfer header
> and pages themselves, so merge them into one single
> call.
> 
> Signed-off-by: Pavel Emelyanov <xemul at virtuozzo.com>
> ---
>  criu/include/page-xfer.h |  3 +--
>  criu/page-xfer.c         | 22 ++++++++++++++++++++--
>  criu/pagemap.c           | 14 ++------------
>  3 files changed, 23 insertions(+), 16 deletions(-)
> 
> diff --git a/criu/include/page-xfer.h b/criu/include/page-xfer.h
> index 0b92ec9..5d8dc81 100644
> --- a/criu/include/page-xfer.h
> +++ b/criu/include/page-xfer.h
> @@ -60,11 +60,10 @@ extern int check_parent_page_xfer(int fd_type, long id);
>  
>  /* async request/receive of remote pages */
>  extern int request_remote_pages(int pid, unsigned long addr, int nr_pages);
> -extern int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid);
> -extern int receive_remote_pages(int len, void *buf);
>  
>  typedef int (*ps_async_read_complete)(int pid, unsigned long vaddr, int nr_pages, void *);
>  extern int page_server_start_async_read(void *buf, int nr_pages,
>  		ps_async_read_complete complete, void *priv);
> +extern int page_server_start_sync_read(void *buf, int nr_pages, unsigned long *vaddr);
>  
>  #endif /* __CR_PAGE_XFER__H__ */
> diff --git a/criu/page-xfer.c b/criu/page-xfer.c
> index c557407..761985a 100644
> --- a/criu/page-xfer.c
> +++ b/criu/page-xfer.c
> @@ -1174,7 +1174,7 @@ int request_remote_pages(int pid, unsigned long addr, int nr_pages)
>  	return 0;
>  }
>  
> -int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid)
> +static int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid)
>  {
>  	struct page_server_iov pi;
>  
> @@ -1194,7 +1194,7 @@ int receive_remote_pages_info(int *nr_pages, unsigned long *addr, int *pid)
>  	return 0;
>  }
>  
> -int receive_remote_pages(int len, void *buf)
> +static int receive_remote_pages(int len, void *buf)
>  {
>  	if (recv(page_server_sk, buf, len, MSG_WAITALL) != len) {
>  		pr_perror("Failed to receive page data");
> @@ -1203,3 +1203,21 @@ int receive_remote_pages(int len, void *buf)
>  
>  	return 0;
>  }
> +
> +int page_server_start_sync_read(void *buf, int nr, unsigned long *vaddr)
> +{
> +	int ret, pid, new_nr;
> +
> +	/*
> +	 * Note, that for async remote page_read, the actual
> +	 * transfer happens in the lazy-pages daemon
> +	 */
> +	ret = receive_remote_pages_info(&new_nr, vaddr, &pid);
> +	if (ret == 0) {
> +		if (new_nr < 0 || new_nr > nr)
> +			return -1;

To be completely on the safe side we should also take care of the case when
new_nr < nr. With current implementation of remote lazy-pages this should
not happen because both dump and restore sides see identical iovecs, but we
may extend usage of read_page_remote, e.g. for the image-less case
(--remote). I think adding

nr = new_nr;

here will do the right thing.

> +		ret = receive_remote_pages(nr * PAGE_SIZE, buf);
> +	}
> +
> +	return ret;
> +}
> diff --git a/criu/pagemap.c b/criu/pagemap.c
> index d770e81..06264a1 100644
> --- a/criu/pagemap.c
> +++ b/criu/pagemap.c
> @@ -466,7 +466,7 @@ static int read_page_complete(int pid, unsigned long vaddr, int nr_pages, void *
>  static int maybe_read_page_remote(struct page_read *pr, unsigned long vaddr,
>  				  int nr, void *buf, unsigned flags)
>  {
> -	int ret, pid, new_nr;
> +	int ret;
>  
>  	/* We always do PR_ASAP mode here (FIXME?) */
>  	ret = request_remote_pages(pr->pid, vaddr, nr);
> @@ -475,17 +475,7 @@ static int maybe_read_page_remote(struct page_read *pr, unsigned long vaddr,
>  	if (flags & PR_ASYNC)
>  		return page_server_start_async_read(buf, nr, read_page_complete, pr);
>  
> -	/*
> -	 * Note, that for async remote page_read, the actual
> -	 * transfer happens in the lazy-pages daemon
> -	 */
> -	ret = receive_remote_pages_info(&new_nr, &vaddr, &pid);
> -	if (ret == 0) {
> -		if (new_nr < 0 || new_nr > nr)
> -			return -1;
> -		ret = receive_remote_pages(nr * PAGE_SIZE, buf);
> -	}
> -
> +	ret = page_server_start_sync_read(buf, nr, &vaddr);
>  	if (ret == 0 && pr->io_complete)
>  		ret = pr->io_complete(pr, vaddr, nr);
>  
> -- 
> 2.1.4
> 
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