page-server: Introduce page_server_start_sync_read

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@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/include/page-xfer.h

@@ -55,11 +55,10 @@ 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__ */

criu/page-xfer.c

@@ -1171,7 +1171,7 @@ 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;
 
@@ -1191,7 +1191,7 @@ 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");
@@ -1200,3 +1200,21 @@ 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;
+		ret = receive_remote_pages(nr * PAGE_SIZE, buf);
+	}
+
+	return ret;
+}

criu/pagemap.c

@@ -434,7 +434,7 @@ 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);
@@ -443,17 +443,7 @@ 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);