page-server: Don't setup options in parent task

When service starts page server all the preparations (log, wdir, img dir, etc.)
happen in parent task, then we fork page server.

This is OK for now, but when we will serve several requests per connection, all
these resources would be leaked in parent.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-service.c

@@ -496,7 +496,7 @@ static int pre_dump_loop(int sk, CriuReq *msg)
 
 static int start_page_server_req(int sk, CriuOpts *req)
 {
-	int ret;
+	int ret, pid, start_pipe[2];
 	bool success = false;
 	CriuResp resp = CRIU_RESP__INIT;
 	CriuPageServerInfo ps = CRIU_PAGE_SERVER_INFO__INIT;
@@ -506,14 +506,33 @@ static int start_page_server_req(int sk, CriuOpts *req)
 		goto out;
 	}
 
-	if (setup_opts_from_req(sk, req))
+	if (pipe(start_pipe)) {
+		pr_perror("No start pipe");
 		goto out;
+	}
+
+	pid = fork();
+	if (pid == 0) {
+		close(start_pipe[0]);
+
+		if (setup_opts_from_req(sk, req))
+			goto out_ch;
 
 		setproctitle("page-server --rpc --address %s --port %hu", opts.addr, opts.ps_port);
 
 		pr_debug("Starting page server\n");
 
-	ret = cr_page_server(true);
+		ret = cr_page_server(true, start_pipe[1]);
+out_ch:
+		write(start_pipe[1], &ret, sizeof(ret));
+		close(start_pipe[1]);
+		exit(0);
+	}
+
+	close(start_pipe[1]);
+	wait(NULL);
+	ret = -1;
+	read(start_pipe[0], &ret, sizeof(ret));
 	if (ret > 0) {
 		success = true;
 		ps.has_pid = true;

crtools.c

@@ -496,7 +496,7 @@ int main(int argc, char *argv[], char *envp[])
 	}
 
 	if (!strcmp(argv[optind], "page-server"))
-		return cr_page_server(opts.restore_detach) > 0 ? 0 : 1;
+		return cr_page_server(opts.restore_detach, -1) > 0 ? 0 : 1;
 
 	if (!strcmp(argv[optind], "service"))
 		return cr_service(opts.restore_detach);

include/page-xfer.h

@@ -2,7 +2,7 @@
 #define __CR_PAGE_XFER__H__
 #include "page-read.h"
 
-extern int cr_page_server(bool daemon_mode);
+extern int cr_page_server(bool daemon_mode, int cfd);
 
 /*
  * page_xfer -- transfer pages into image file.

include/util.h

@@ -263,7 +263,7 @@ extern void *shmalloc(size_t bytes);
 extern void shfree_last(void *ptr);
 
 extern int cr_system(int in, int out, int err, char *cmd, char *const argv[]);
-extern int cr_daemon(int nochdir, int noclose);
+extern int cr_daemon(int nochdir, int noclose, int *keep_fd, int close_fd);
 extern int is_root_user(void);
 
 static inline bool dir_dots(struct dirent *de)

page-xfer.c

@@ -254,7 +254,7 @@ static int get_sockaddr_in(struct sockaddr_in *addr)
 	return 0;
 }
 
-int cr_page_server(bool daemon_mode)
+int cr_page_server(bool daemon_mode, int cfd)
 {
 	int sk = -1, ask = -1, ret;
 	struct sockaddr_in saddr, caddr;
@@ -292,7 +292,7 @@ int cr_page_server(bool daemon_mode)
 
 no_server:
 	if (daemon_mode) {
-		ret = cr_daemon(1, 0);
+		ret = cr_daemon(1, 0, &ask, cfd);
 		if (ret == -1) {
 			pr_perror("Can't run in the background");
 			goto out;

util.c

@@ -560,7 +560,7 @@ out:
 	return ret;
 }
 
-int cr_daemon(int nochdir, int noclose)
+int cr_daemon(int nochdir, int noclose, int *keep_fd, int close_fd)
 {
 	int pid;
 
@@ -580,6 +580,12 @@ int cr_daemon(int nochdir, int noclose)
 	if (!noclose) {
 		int fd;
 
+		if (close_fd != -1)
+			close(close_fd);
+
+		if (*keep_fd != -1)
+			*keep_fd = dup2(*keep_fd, 3);
+
 		fd = open("/dev/null", O_RDWR);
 		if (fd < 0) {
 			pr_perror("Can't open /dev/null");