Return ECGROUPNOTEQUAL to indicate partial create success

Return ECGROUPNOTEQUAL when copying controller parameters fails--
this allows callers to differentiate between cgroup creation failures and
controller configuration failures, and makes explicit that this function
can return an error code but still have created the cgroup.  Callers,
such as cgroup_create_cgroup_from_parent(), can now explicitly ignore
(the unfortunately expected) controller configuration errors.

Signed-off-by: Eric Brower <ebrower@gmail.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Dhaval Giani <dhaval.giani@gmail.com>

diff --git a/src/api.c b/src/api.c
index dcdd75b4bde35821ba0b04568b812c753e9826cb..c8332f98f7bf4e6758bce817059ad44dfb688284 100644 (file)
--- a/src/api.c
+++ b/src/api.c
@@ -1310,6 +1310,8 @@ err:
  *
  * returns 0 on success. We recommend calling cg_delete_cgroup
  * if this routine fails. That should do the cleanup operation.
+ * If ECGROUPNOTEQUAL is returned, the group was created successfully
+ * but not all controller parameters were successfully set.
  */
 int cgroup_create_cgroup(struct cgroup *cgroup, int ignore_ownership)
 {
@@ -1374,8 +1376,8 @@ int cgroup_create_cgroup(struct cgroup *cgroup, int ignore_ownership)
                for (j = 0; j < cgroup->controller[k]->index; j++) {
                        ret = snprintf(path, FILENAME_MAX, "%s%s", base,
                                        cgroup->controller[k]->values[j]->name);
-                       cgroup_dbg("setting %s to %s, error %d\n", path,
-                               cgroup->controller[k]->values[j]->name, ret);
+                       cgroup_dbg("setting %s to \"%s\", pathlen %d\n", path,
+                               cgroup->controller[k]->values[j]->value, ret);
                        if (ret < 0 || ret >= FILENAME_MAX) {
                                last_errno = errno;
                                error = ECGOTHER;
@@ -1390,10 +1392,15 @@ int cgroup_create_cgroup(struct cgroup *cgroup, int ignore_ownership)
                         * are only conditionally created in the child.
                         *
                         * A middle ground would be to track that there
-                        * was an error and return that value.
+                        * was an error and return a diagnostic value--
+                        * callers don't get context for the error, but can
+                        * ignore it specifically if they wish.
                         */
                        if (error) {
-                               retval = error;
+                               cgroup_dbg("failed to set %s: %s (%d)\n",
+                                       path,
+                                       cgroup_strerror(error), error);
+                               retval = ECGROUPNOTEQUAL;
                                continue;
                        }
                }
@@ -1508,6 +1515,9 @@ free_parent:
  * @cgroup: cgroup data structure to be filled with parent values and then
  *       passed down for creation
  * @ignore_ownership: Ignore doing a chown on the newly created cgroup
+ * @return 0 on success, > 0 on failure.  If ECGROUPNOTEQUAL is returned,
+ * the group was created successfully, but not all controller parameters
+ * were copied from the parent successfully; unfortunately, this is expected...
  */
 int cgroup_create_cgroup_from_parent(struct cgroup *cgroup,
                                        int ignore_ownership)