pstree: Change type of init_pstree_helper() and check for parent

This is refactoring, which will be used in next patches.
BUG_ON() just to mention that parent must be set before
call of this function.

v5: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/files-reg.c

@@ -532,13 +532,16 @@ static int collect_remap_dead_process(struct reg_file_info *rfi,
 		return 0;
 	}
 
-	init_pstree_helper(helper);
 
 	helper->sid = root_item->sid;
 	helper->pgid = root_item->pgid;
 	helper->pid->ns[0].virt = rfe->remap_id;
 	helper->parent = root_item;
 	helper->ids = root_item->ids;
+	if (init_pstree_helper(helper)) {
+		pr_err("Can't init helper\n");
+		return -1;
+	}
 	list_add_tail(&helper->sibling, &root_item->children);
 
 	pr_info("Added a helper for restoring /proc/%d\n", vpid(helper));

criu/include/pstree.h

@@ -87,7 +87,7 @@ static inline bool task_alive(struct pstree_item *i)
 extern void free_pstree(struct pstree_item *root_item);
 extern struct pstree_item *__alloc_pstree_item(bool rst);
 #define alloc_pstree_item() __alloc_pstree_item(false)
-extern void init_pstree_helper(struct pstree_item *ret);
+extern int init_pstree_helper(struct pstree_item *ret);
 
 extern struct pstree_item *lookup_create_item(pid_t pid);
 extern void pstree_insert_pid(struct pid *pid_node);

criu/pstree.c

@@ -229,11 +229,13 @@ struct pstree_item *__alloc_pstree_item(bool rst)
 	return item;
 }
 
-void init_pstree_helper(struct pstree_item *ret)
+int init_pstree_helper(struct pstree_item *ret)
 {
+	BUG_ON(!ret->parent);
 	ret->pid->state = TASK_HELPER;
 	rsti(ret)->clone_flags = CLONE_FILES | CLONE_FS;
 	task_entries->nr_helpers++;
+	return 0;
 }
 
 /* Deep first search on children */
@@ -675,7 +677,10 @@ static int prepare_pstree_ids(void)
 			helper->ids = root_item->ids;
 			list_add_tail(&helper->sibling, &helpers);
 		}
-		init_pstree_helper(helper);
+		if (init_pstree_helper(helper)) {
+			pr_err("Can't init helper\n");
+			return -1;
+		}
 
 		pr_info("Add a helper %d for restoring SID %d\n",
 				vpid(helper), helper->sid);
@@ -763,13 +768,16 @@ static int prepare_pstree_ids(void)
 			continue;
 
 		helper = pid->item;
-		init_pstree_helper(helper);
 
 		helper->sid = item->sid;
 		helper->pgid = item->pgid;
 		helper->pid->ns[0].virt = item->pgid;
 		helper->parent = item;
 		helper->ids = item->ids;
+		if (init_pstree_helper(helper)) {
+			pr_err("Can't init helper\n");
+			return -1;
+		}
 		list_add(&helper->sibling, &item->children);
 		rsti(item)->pgrp_leader = helper;