From: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Date: Thu, 31 Mar 2022 12:21:55 +0000 (+0530)
Subject: api.c: add support for empty cgroup v2 deletion
X-Git-Tag: v3.0~93
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ca55c929e8074e630f3fd2eded96542b88ef1ad5;p=thirdparty%2Flibcgroup.git

api.c: add support for empty cgroup v2 deletion

Add support to recognize empty cgroup v2 with no controllers attached to
it in cgroup_delete_cgroup_ext(), that gets called to remove a cgroup.

In the deletion path, cgroup_build_tasks_procs_path() builds the path
of the cgroup for re-assignment/movement of tasks from the cgroup that's
getting deleted, teach it to recognize the empty controller as cgroup
V2.

Fixes: https://github.com/libcgroup/libcgroup/issues/125

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
TJH: Fix a couple small typos in commit message
---

diff --git a/src/api.c b/src/api.c
index a1fc4a0d..1c4eaa33 100644
--- a/src/api.c
+++ b/src/api.c
@@ -3083,9 +3083,11 @@ int cgroup_delete_cgroup_ext(struct cgroup *cgroup, int flags)
 {
 	int first_error = 0, first_errno = 0;
 	char parent_path[FILENAME_MAX];
+	char *controller_name = NULL;
 	FILE *parent_tasks = NULL;
 	char *parent_name = NULL;
 	int delete_group = 1;
+	int empty_cgroup = 0;
 	int i, ret;
 
 	if (!cgroup_initialized)
@@ -3098,19 +3100,31 @@ int cgroup_delete_cgroup_ext(struct cgroup *cgroup, int flags)
 	    && (flags & CGFLAG_DELETE_EMPTY_ONLY))
 		return ECGINVAL;
 
+	if (cgroup->index == 0)
+		/* Valid empty cgroup v2 with not controllers added. */
+		empty_cgroup = 1;
+
 	for (i = 0; i < cgroup->index; i++) {
 		if (!cgroup_test_subsys_mounted(cgroup->controller[i]->name))
 			return ECGROUPSUBSYSNOTMOUNTED;
 	}
 
-	/* Remove the group from all controllers. */
-	for (i = 0; i < cgroup->index; i++) {
+	/*
+	 * Remove the group from all controllers and in the case of cgroup
+	 * with no controllers, perform all actions of a single controller.
+	 */
+	for (i = 0;
+	     empty_cgroup > 0 || i < cgroup->index; i++, empty_cgroup--) {
+
 		ret = 0;
+		controller_name = NULL;
+
+		if (cgroup->controller[i])
+			controller_name = cgroup->controller[i]->name;
 
 		/* Find parent, it can be different for each controller */
 		if (!(flags & CGFLAG_DELETE_EMPTY_ONLY)) {
-			ret = cgroup_find_parent(cgroup,
-						 cgroup->controller[i]->name,
+			ret = cgroup_find_parent(cgroup, controller_name,
 						 &parent_name);
 			if (ret) {
 				if (first_error == 0) {
@@ -3147,7 +3161,7 @@ int cgroup_delete_cgroup_ext(struct cgroup *cgroup, int flags)
 			/* Tasks need to be moved, pre-open target tasks file */
 			ret = cgroup_build_tasks_procs_path(parent_path,
 					sizeof(parent_path), parent_name,
-					cgroup->controller[i]->name);
+					controller_name);
 			if (ret != 0) {
 				if (first_error == 0)
 					first_error = ECGFAIL;
@@ -3171,12 +3185,12 @@ int cgroup_delete_cgroup_ext(struct cgroup *cgroup, int flags)
 		if (flags & CGFLAG_DELETE_RECURSIVE) {
 			ret = cg_delete_cgroup_controller_recursive(
 					cgroup->name,
-					cgroup->controller[i]->name,
+					controller_name,
 					parent_tasks, flags,
 					delete_group);
 		} else {
 			ret = cg_delete_cgroup_controller(cgroup->name,
-					cgroup->controller[i]->name,
+					controller_name,
 					parent_tasks, flags);
 		}
 
@@ -5940,6 +5954,11 @@ int cgroup_get_controller_version(const char * const controller,
 	if (!version)
 		return ECGINVAL;
 
+	if (!controller && strlen(cg_cgroup_v2_mount_path) > 0) {
+		*version = CGROUP_V2;
+		return 0;
+	}
+
 	*version = CGROUP_UNK;
 
 	for (i = 0; cg_mount_table[i].name[0] != '\0'; i++) {