libcgroup: added new flag to cgroup_delete_cgroup_ext to delete only empty groups

New flag CGFLAG_DELETE_EMPTY_ONLY tells cgroup_delete_cgroup_ext that the
group being deleted must be empty, i.e. have no subgroups and no tasks
inside.

Signed-off-by: Jan Safranek <jsafrane@redhat.com>

diff --git a/include/libcgroup/groups.h b/include/libcgroup/groups.h
index 86c5b76612d9d4356c2cdb1574af8cbee6467553..f375a824cea3e4f69cf0eff878b797d91a841f65 100644 (file)
--- a/include/libcgroup/groups.h
+++ b/include/libcgroup/groups.h
@@ -26,6 +26,13 @@ enum cgroup_delete_flag {
         * Recursively delete all child groups.
         */
        CGFLAG_DELETE_RECURSIVE = 2,
+
+       /**
+        * Delete the cgroup only if it is empty, i.e. it has no subgroups and
+        * no processes inside. This flag cannot be used with
+        * CGFLAG_DELETE_RECURSIVE.
+        */
+       CGFLAG_DELETE_EMPTY_ONLY        = 4,
 };
 
 /**

diff --git a/src/api.c b/src/api.c
index 663c6a7c51ab2770d21210e77b3a287062459835..e2e4189b01e83a37a44d8e834637719fec7e4657 100644 (file)
--- a/src/api.c
+++ b/src/api.c
@@ -1871,30 +1871,33 @@ static int cg_delete_cgroup_controller(char *cgroup_name, char *controller,
 
        cgroup_dbg("Removing group %s:%s\n", controller, cgroup_name);
 
-       /*
-        * Open tasks file of the group to delete.
-        */
-       if (!cg_build_path(cgroup_name, path, controller))
-               return ECGROUPSUBSYSNOTMOUNTED;
-       strncat(path, "tasks", sizeof(path) - strlen(path));
-
-       delete_tasks = fopen(path, "re");
-       if (delete_tasks) {
-               ret = cg_move_task_files(delete_tasks, target_tasks);
-               fclose(delete_tasks);
-       } else {
+       if (!(flags & CGFLAG_DELETE_EMPTY_ONLY)) {
                /*
-                * Can't open the tasks file. If the file does not exist, ignore
-                * it - the group has been already removed.
+                * Open tasks file of the group to delete.
                 */
-               if (errno != ENOENT) {
-                       last_errno = errno;
-                       ret = ECGOTHER;
+               if (!cg_build_path(cgroup_name, path, controller))
+                       return ECGROUPSUBSYSNOTMOUNTED;
+               strncat(path, "tasks", sizeof(path) - strlen(path));
+
+               delete_tasks = fopen(path, "re");
+               if (delete_tasks) {
+                       ret = cg_move_task_files(delete_tasks, target_tasks);
+                       fclose(delete_tasks);
+               } else {
+                       /*
+                        * Can't open the tasks file. If the file does not
+                        * exist, ignore it - the group has been already
+                        * removed.
+                        */
+                       if (errno != ENOENT) {
+                               last_errno = errno;
+                               ret = ECGOTHER;
+                       }
                }
-       }
 
-       if (ret != 0 && !(flags & CGFLAG_DELETE_IGNORE_MIGRATION))
-               return ret;
+               if (ret != 0 && !(flags & CGFLAG_DELETE_IGNORE_MIGRATION))
+                       return ret;
+       }
 
        /*
         * Remove the group.
@@ -2009,35 +2012,41 @@ int cgroup_delete_cgroup_ext(struct cgroup *cgroup, int flags)
        if (!cgroup)
                return ECGROUPNOTALLOWED;
 
+       if ((flags & CGFLAG_DELETE_RECURSIVE)
+                       && (flags & CGFLAG_DELETE_EMPTY_ONLY))
+               return ECGINVAL;
+
        for (i = 0; i < cgroup->index; i++) {
                if (!cgroup_test_subsys_mounted(cgroup->controller[i]->name))
                        return ECGROUPSUBSYSNOTMOUNTED;
        }
 
-       ret = cgroup_find_parent(cgroup, &parent_name);
-       if (ret)
-               return ret;
+       if (!(flags & CGFLAG_DELETE_EMPTY_ONLY)) {
+               ret = cgroup_find_parent(cgroup, &parent_name);
+               if (ret)
+                       return ret;
 
-       if (parent_name == NULL) {
-               /*
-                * Root group is being deleted.
-                */
-               if (flags & CGFLAG_DELETE_RECURSIVE) {
+               if (parent_name == NULL) {
                        /*
-                        * Move all tasks to the root group and do not delete
-                        * it afterwards.
+                        * Root group is being deleted.
                         */
-                       parent_name = strdup(".");
-                       if (parent_name == NULL) {
-                               last_errno = errno;
+                       if (flags & CGFLAG_DELETE_RECURSIVE) {
+                               /*
+                                * Move all tasks to the root group and do not
+                                * delete it afterwards.
+                                */
+                               parent_name = strdup(".");
+                               if (parent_name == NULL) {
+                                       last_errno = errno;
                                return ECGOTHER;
-                       }
-                       delete_group = 0;
-               } else
-                       /*
-                        *  TODO: should it succeed?
-                        */
-                       return 0;
+                               }
+                               delete_group = 0;
+                       } else
+                               /*
+                                *  TODO: should it succeed?
+                                */
+                               return 0;
+               }
        }
 
        /*
@@ -2046,18 +2055,22 @@ int cgroup_delete_cgroup_ext(struct cgroup *cgroup, int flags)
        for (i = 0; i < cgroup->index; i++) {
                ret = 0;
 
-               if (!cg_build_path(parent_name, parent_path,
+               if (parent_name) {
+                       /* tasks need to be moved, pre-open target tasks file */
+                       if (!cg_build_path(parent_name, parent_path,
                                        cgroup->controller[i]->name))
-                       continue;
+                               continue;
 
-               strncat(parent_path, "/tasks", sizeof(parent_path)
-                               - strlen(parent_path));
+                       strncat(parent_path, "/tasks", sizeof(parent_path)
+                                       - strlen(parent_path));
 
-               parent_tasks = fopen(parent_path, "we");
-               if (!parent_tasks) {
-                       last_errno = errno;
-                       ret = ECGOTHER;
-               } else {
+                       parent_tasks = fopen(parent_path, "we");
+                       if (!parent_tasks) {
+                               last_errno = errno;
+                               ret = ECGOTHER;
+                       }
+               }
+               if (parent_tasks || !parent_name) {
                        if (flags & CGFLAG_DELETE_RECURSIVE) {
                                ret = cg_delete_cgroup_controller_recursive(
                                                cgroup->name,
@@ -2069,7 +2082,8 @@ int cgroup_delete_cgroup_ext(struct cgroup *cgroup, int flags)
                                                cgroup->controller[i]->name,
                                                parent_tasks, flags);
                        }
-                       fclose(parent_tasks);
+                       if (parent_tasks)
+                               fclose(parent_tasks);
                }
 
                /*