page-server: Unify async/sync calls

The newly introduced sync-read call may look exactly
the same as its async pair by using the respective
complete callback.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/include/page-xfer.h

@@ -59,6 +59,7 @@ extern int request_remote_pages(int pid, unsigned long addr, int nr_pages);
 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);
+extern int page_server_start_sync_read(void *buf, int nr_pages,
+		ps_async_read_complete complete, void *priv);
 
 #endif /* __CR_PAGE_XFER__H__ */

criu/page-xfer.c

@@ -1201,20 +1201,25 @@ static int receive_remote_pages(int len, void *buf)
 	return 0;
 }
 
-int page_server_start_sync_read(void *buf, int nr, unsigned long *vaddr)
+int page_server_start_sync_read(void *buf, int nr,
+		ps_async_read_complete complete, void *priv)
 {
 	int ret, pid, new_nr;
+	unsigned long vaddr;
 
 	/*
 	 * 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);
+	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);
 	}
 
+	if (ret == 0)
+		ret = complete(pid, vaddr, nr, priv);
+
 	return ret;
 }

criu/pagemap.c

@@ -442,12 +442,8 @@ static int maybe_read_page_remote(struct page_read *pr, unsigned long vaddr,
 		return ret;
 	if (flags & PR_ASYNC)
 		return page_server_start_async_read(buf, nr, read_page_complete, pr);
-
-	ret = page_server_start_sync_read(buf, nr, &vaddr);
-	if (ret == 0 && pr->io_complete)
-		ret = pr->io_complete(pr, vaddr, nr);
-
-	return ret;
+	else
+		return page_server_start_sync_read(buf, nr, read_page_complete, pr);
 }
 
 static int read_pagemap_page(struct page_read *pr, unsigned long vaddr, int nr,