uffdd: Implement --daemon mode

Right now the zdtm.py hacks around core code and waits for
a second for the socket to appear. Let's better make proper
--daemon mode for lazy-pages daemon and pidfile generation.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>

criu/crtools.c

@@ -738,7 +738,7 @@ int main(int argc, char *argv[], char *envp[])
 	}
 
 	if (!strcmp(argv[optind], "lazy-pages"))
-		return cr_lazy_pages() != 0;
+		return cr_lazy_pages(opts.daemon_mode) != 0;
 
 	if (!strcmp(argv[optind], "check"))
 		return cr_check() != 0;

criu/include/crtools.h

@@ -25,7 +25,7 @@ extern int cr_restore_tasks(void);
 extern int convert_to_elf(char *elf_path, int fd_core);
 extern int cr_check(void);
 extern int cr_dedup(void);
-extern int cr_lazy_pages(void);
+extern int cr_lazy_pages(bool daemon);
 
 extern int check_add_feature(char *arg);
 extern void pr_check_features(const char *offset, const char *sep, int width);

criu/uffd.c

@@ -15,12 +15,13 @@
 #include <sys/un.h>
 #include <sys/socket.h>
 #include <sys/epoll.h>
+#include <sys/wait.h>
 
 #include "linux/userfaultfd.h"
 
 #include "int.h"
 #include "page.h"
-#include "log.h"
+#include "criu-log.h"
 #include "criu-plugin.h"
 #include "pagemap.h"
 #include "files-reg.h"
@@ -776,12 +777,9 @@ static int epoll_add_lpi(int epollfd, struct lazy_pages_info *lpi)
 	return 0;
 }
 
-static int prepare_uffds(int epollfd)
+static int prepare_lazy_socket(void)
 {
-	int i;
 	int listen;
-	int client;
-	socklen_t len;
 	struct sockaddr_un saddr;
 
 	if (prepare_sock_addr(&saddr))
@@ -793,6 +791,16 @@ static int prepare_uffds(int epollfd)
 		return -1;
 	}
 
+	return listen;
+}
+
+static int prepare_uffds(int listen, int epollfd)
+{
+	int i;
+	int client;
+	socklen_t len;
+	struct sockaddr_un saddr;
+
 	/* accept new client request */
 	len = sizeof(struct sockaddr_un);
 	if ((client = accept(listen, (struct sockaddr *) &saddr, &len)) < 0) {
@@ -822,10 +830,11 @@ close_uffd:
 	return -1;
 }
 
-int cr_lazy_pages()
+int cr_lazy_pages(bool daemon)
 {
 	struct epoll_event *events;
 	int epollfd;
+	int lazy_sk;
 	int ret;
 
 	if (check_for_uffd())
@@ -834,11 +843,38 @@ int cr_lazy_pages()
 	if (lazy_pages_prepare_pstree())
 		return -1;
 
+	lazy_sk = prepare_lazy_socket();
+	if (lazy_sk < 0)
+		return -1;
+
+	if (daemon) {
+		ret = cr_daemon(1, 0, &lazy_sk, -1);
+		if (ret == -1) {
+			pr_err("Can't run in the background\n");
+			return -1;
+		}
+		if (ret > 0) { /* parent task, daemon started */
+			if (opts.pidfile) {
+				if (write_pidfile(ret) == -1) {
+					pr_perror("Can't write pidfile");
+					kill(ret, SIGKILL);
+					waitpid(ret, NULL, 0);
+					return -1;
+				}
+			}
+
+			return 0;
+		}
+	}
+
+	if (close_status_fd())
+		return -1;
+
 	epollfd = prepare_epoll(task_entries->nr_tasks, &events);
 	if (epollfd < 0)
 		return -1;
 
-	if (prepare_uffds(epollfd))
+	if (prepare_uffds(lazy_sk, epollfd))
 		return -1;
 
 	if (connect_to_page_server())

test/zdtm.py

@@ -962,11 +962,9 @@ class criu:
 			r_opts.append('--external')
 			r_opts.append('mnt[zdtm]:%s' % criu_dir)
 
-		lazy_pages_p = None
 		if self.__lazy_pages:
-			lazy_pages_p = self.__criu_act("lazy-pages", opts = [], nowait = True)
+			self.__criu_act("lazy-pages", opts = ["--daemon", "--pidfile", "lp.pid"])
 			r_opts += ["--lazy-pages"]
-			time.sleep(1)  # FIXME wait user fault fd socket
 
 		if self.__leave_stopped:
 			r_opts += ['--leave-stopped']
@@ -989,8 +987,8 @@ class criu:
 			pstree_check_stopped(self.__test.getpid())
 			pstree_signal(self.__test.getpid(), signal.SIGCONT)
 
-		if lazy_pages_p and lazy_pages_p.wait():
-			raise test_fail_exc("CRIU lazy-pages")
+		if self.__lazy_pages:
+			wait_pid_die(int(rpidfile(self.__ddir() + "/lp.pid")), "lazy pages daemon")
 
 	@staticmethod
 	def check(feature):