restore: Pass self-vma file descriptor directly

Instead of passing self-vma file path to restorer
code simply open it before restore_task call and
pass descriptor instead. This saves some memory.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

cr-restore.c

@@ -1341,8 +1341,16 @@ static void sigreturn_restore(pid_t pstree_pid, pid_t pid)
 
 	if (get_image_path(self_vmas_path, sizeof(self_vmas_path), FMT_FNAME_VMAS, getpid()))
 		goto err;
+
+	fd_self_vmas = open(self_vmas_path, O_CREAT | O_RDWR | O_TRUNC, CR_FD_PERM);
+
+	/*
+	 * This is a temporary file used to pass vma info to
+	 * restorer code, thus unlink it early to make it disappear
+	 * as soon as we close it
+	 */
 	unlink(self_vmas_path);
-	fd_self_vmas = open(self_vmas_path, O_CREAT | O_RDWR, CR_FD_PERM);
+
 	if (fd_self_vmas < 0) {
 		pr_perror("Can't open %s\n", self_vmas_path);
 		goto err;
@@ -1482,9 +1490,6 @@ static void sigreturn_restore(pid_t pstree_pid, pid_t pid)
 	task_args->fd_core	= fd_core;
 	task_args->fd_self_vmas	= fd_self_vmas;
 	task_args->shmems_fd	= ret;
-	strncpy(task_args->self_vmas_path,
-		self_vmas_path,
-		sizeof(task_args->self_vmas_path));
 
 	cr_mutex_init(&task_args->rst_lock);
 

include/restorer.h

@@ -66,7 +66,6 @@ struct task_restore_core_args {
 	int				fd_core;		/* opened core file */
 	int				fd_self_vmas;		/* opened file with running VMAs to unmap */
 	union {
-		char			self_vmas_path[PATH_MAX];/* path to it, to unlink it once we're done */
 		char			last_pid_buf[PATH_MAX];	/* internal buffer to save stack space  */
 	};
 	char				ns_last_pid_path[PATH_MAX];

restorer.c

@@ -211,7 +211,6 @@ self_len_end:
 		}
 
 		sys_close(args->fd_self_vmas);
-		sys_unlink(args->self_vmas_path);
 
 		/*
 		 * OK, lets try to map new one.