dump: Allocate root_item before run pre-dump scripts

This allows pre-dump scripts to know CT root_item pid
and enter into its namespaces.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cr-dump.c

@@ -1471,6 +1471,11 @@ int cr_pre_dump_tasks(pid_t pid)
 	int ret = -1;
 	LIST_HEAD(ctls);
 
+	root_item = alloc_pstree_item();
+	if (!root_item)
+		goto err;
+	root_item->pid.real = pid;
+
 	if (!opts.track_mem) {
 		pr_info("Enforcing memory tracking for pre-dump.\n");
 		opts.track_mem = true;
@@ -1505,7 +1510,7 @@ int cr_pre_dump_tasks(pid_t pid)
 	if (setup_alarm_handler())
 		goto err;
 
-	if (collect_pstree(pid))
+	if (collect_pstree())
 		goto err;
 
 	if (collect_pstree_ids_predump())
@@ -1616,6 +1621,11 @@ int cr_dump_tasks(pid_t pid)
 	pr_info("Dumping processes (pid: %d)\n", pid);
 	pr_info("========================================\n");
 
+	root_item = alloc_pstree_item();
+	if (!root_item)
+		goto err;
+	root_item->pid.real = pid;
+
 	pre_dump_ret = run_scripts(ACT_PRE_DUMP);
 	if (pre_dump_ret != 0) {
 		pr_err("Pre dump script failed with %d!\n", pre_dump_ret);
@@ -1668,7 +1678,7 @@ int cr_dump_tasks(pid_t pid)
 	 * afterwards.
 	 */
 
-	if (collect_pstree(pid))
+	if (collect_pstree())
 		goto err;
 
 	if (collect_pstree_ids())

criu/include/seize.h

 #ifndef __CR_SEIZE_H__
 #define __CR_SEIZE_H__
 
-extern int collect_pstree(pid_t pid);
+extern int collect_pstree(void);
 extern void pstree_switch_state(struct pstree_item *root_item, int st);
 extern const char *get_real_freezer_state(void);
 extern bool alarm_timeouted(void);

criu/seize.c

@@ -650,8 +650,9 @@ err_close:
 	return -1;
 }
 
-int collect_pstree(pid_t pid)
+int collect_pstree(void)
 {
+	pid_t pid = root_item->pid.real;
 	int ret = -1;
 
 	timing_start(TIME_FREEZING);
@@ -666,12 +667,6 @@ int collect_pstree(pid_t pid)
 	if (opts.freeze_cgroup && freeze_processes())
 		goto err;
 
-	root_item = alloc_pstree_item();
-	if (root_item == NULL)
-		goto err;
-
-	root_item->pid.real = pid;
-
 	if (!opts.freeze_cgroup && seize_catch_task(pid)) {
 		set_cr_errno(ESRCH);
 		goto err;