Split cgroup_find_parent cgroup/parent on-disk validation from cgroup parent
name generation. This solves a chicken-and-egg problem for callers that need
to obtain a parent name from a cgroup that has not yet been created, such as
cgroup_create_cgroup_from_parent(). The new function enforces the documented
behavior (return NULL) when a "root" cgroup is specified.
Modify cgroup_create_cgroup_from_parent() to use this new function, and clean up
a few possibly-erroneous return values.
diff --git a/src/api.c b/src/api.c
index 4823006..a29fe80 100644
--- a/src/api.c
+++ b/src/api.c
@@ -1428,8 +1435,56 @@ err:
}
/**
+ * Obtain the calculated parent name of specified cgroup; no validation
+ * of the existence of the child or parent group is performed.
+ *
+ * Given the path-like hierarchy of cgroup names, this function returns
+ * the dirname() of the cgroup name as the likely parent name; the caller
+ * is responsible for validating parent as appropriate.
+ *
+ * @param cgroup The cgroup to query for parent's name
+ * @param parent Output, name of parent's group, or NULL if the
+ * provided cgroup is the root group.
+ * Caller is responsible to free the returned string.
+ * @return 0 on success, > 0 on error
+ */
+static int cgroup_get_parent_name(struct cgroup *cgroup, char **parent)
+{
+ int ret = 0;
+ char *dir = NULL;
+ char *pdir = NULL;
+
+ dir = strdup(cgroup->name);
+ if (!dir) {
+ return ECGFAIL;
+ }
+ cgroup_dbg("group name is %s\n", dir);
+
+ pdir = dirname(dir);
+ cgroup_dbg("parent's group name is %s\n", pdir);
+
+ /* check for root group */
+ if (strlen(cgroup->name) == 0 || !strcmp(cgroup->name, pdir)) {
+ cgroup_dbg("specified cgroup \"%s\" is root group\n",
+ cgroup->name);
+ *parent = NULL;
+ }
+ else {
+ *parent = strdup(pdir);
+ }
+ free(dir);
+
+ if (*parent == NULL)
+ ret = ECGFAIL;
+
+ return ret;
+}
+
+/**
* Find the parent of the specified directory. It returns the parent (the
- * parent is usually name/.. unless name is a mount point.
+ * parent is usually name/.. unless name is a mount point. It is assumed
+ * both the cgroup (and, therefore, parent) already exist, and will fail
+ * otherwise.
*
* @param cgroup The cgroup
* @param parent Output, name of parent's group (if the group has parent) or
@@ -1483,20 +1543,7 @@ static int cgroup_find_parent(struct cgroup
*cgroup, char **parent)
ret = 0;
cgroup_dbg("Parent is on different device\n");
} else {
- dir = strdup(cgroup->name);
- cgroup_dbg("group name is %s\n", dir);
- if (!dir) {
- ret = ECGFAIL;
- goto free_parent;
- }
-
- parent_dir = dirname(dir);
- cgroup_dbg("parent's group name is %s\n", parent_dir);
- *parent = strdup(parent_dir);
- free(dir);
-
- if (*parent == NULL)
- ret = ECGFAIL;
+ ret = cgroup_get_parent_name(cgroup, parent);
}
free_parent:
@@ -1519,7 +1569,7 @@ int cgroup_create_cgroup_from_parent(struct
cgroup *cgroup,
if (!cgroup_initialized)
return ECGROUPNOTINITIALIZED;
- ret = cgroup_find_parent(cgroup, &parent);
+ ret = cgroup_get_parent_name(cgroup, &parent);
if (ret)
return ret;
@@ -1533,16 +1583,21 @@ int cgroup_create_cgroup_from_parent(struct
cgroup *cgroup,
cgroup_dbg("parent is %s\n", parent);
parent_cgroup = cgroup_new_cgroup(parent);
- if (!parent_cgroup)
+ if (!parent_cgroup) {
+ ret = ECGFAIL;
goto err_nomem;
+ }
- if (cgroup_get_cgroup(parent_cgroup))
+ if (cgroup_get_cgroup(parent_cgroup)) {
+ ret = ECGFAIL;
goto err_parent;
+ }
cgroup_dbg("got parent group for %s\n", parent_cgroup->name);
ret = cgroup_copy_cgroup(cgroup, parent_cgroup);
- if (ret)
+ if (ret) {
goto err_parent;
+ }
cgroup_dbg("copied parent group %s to %s\n", parent_cgroup->name,
cgroup->name);
--
E
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