Re: [libvirt] [PATCH 3/3] Convert remainder of cgroups code to report errors

19 Jul 2013


      On 07/18/2013 09:00 AM, Daniel P. Berrange wrote:
...
From: "Daniel P. Berrange" <berrange@redhat.com>
Convert the remainiing methods in vircgroup.c to report errors
s/remainiing/remaining/
...
instead of returning errno values.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 src/util/vircgroup.c | 559 +++++++++++++++++++++++++++++----------------------
 1 file changed, 314 insertions(+), 245 deletions(-)

...
@@ -645,29 +661,22 @@ static int virCgroupCpuSetInherit(virCgroupPtr parent, virCgroupPtr group)
     for (i = 0; i < ARRAY_CARDINALITY(inherit_values); i++) {
         char *value;
-        rc = virCgroupGetValueStr(parent,
-                                  VIR_CGROUP_CONTROLLER_CPUSET,
-                                  inherit_values[i],
-                                  &value);
-        if (rc != 0) {
-            virReportSystemError(-rc,
-                                 _("Failed to get '%s'"), inherit_values[i]);
+        if (virCgroupGetValueStr(parent,
+                                 VIR_CGROUP_CONTROLLER_CPUSET,
+                                 inherit_values[i],
+                                 &value) < 0)
Aha - this cleans up something I noticed in 1/3.
...
@@ -675,33 +684,23 @@ static int virCgroupCpuSetInherit(virCgroupPtr parent, virCgroupPtr group)

...
-
-    if (rc != 0) {
-        virReportSystemError(-rc,
-                             _("Failed to set '%s'"), filename);
+    if (virCgroupSetValueU64(group,
+                             VIR_CGROUP_CONTROLLER_MEMORY,
+                             filename, 1) < 0)
         return -1;
-    }
return 0;
Can code like this be simplified to:

return virCgroupSetValueU64(group,
                            VIR_CGROUP_CONTROLLER_MEMORY,
                            filename, 1);
...
@@ -968,11 +964,11 @@ int virCgroupRemove(virCgroupPtr group)
  * @group: The cgroup to add a task to
  * @pid: The pid of the task to add
  *
- * Returns: 0 on success
+ * Returns: 0 on success, -1 on error
  */
 int virCgroupAddTask(virCgroupPtr group, pid_t pid)
Ouch - at least src/qemu/qemu_cgroup.c calls this function, and still
expects errno values:

        rc = virCgroupAddTask(cgroup_vcpu, priv->vcpupids[i]);
        if (rc < 0) {
            virReportSystemError(-rc,
                                 _("unable to add vcpu %zu task %d to
cgroup"),
                                 i, priv->vcpupids[i]);
            goto cleanup;
        }

I didn't look elsewhere; all I needed was one counterexample to state
your patch is incomplete until you audit all callers impacted by
semantic changes.
...
@@ -1019,22 +1023,28 @@ static int virCgroupAddTaskStrController(virCgroupPtr group,
...
+        if (virCgroupAddTaskController(group, p, controller) < 0) {
+            virErrorPtr err = virGetLastError();
+            /* A thread that exits between when we first read the source
+             * tasks and now is not fatal.  */
+            if (err && err->code == VIR_ERR_SYSTEM_ERROR &&
+                err->int1 == ESRCH) {
shorter as 'if (virLastErrorIsSystemErrno(ESRCH))'
...
@@ -1645,18 +1659,30 @@ int virCgroupSetBlkioDeviceWeight(virCgroupPtr group,
...
+    if (stat(path, &sb) < 0) {
+        virReportSystemError(errno,
+                             _("Path '%s' is not accessible"),
+                             path);
+        return -1;
+    }
-    if (!S_ISBLK(sb.st_mode))
-        return -EINVAL;
+    if (!S_ISBLK(sb.st_mode)) {
+        virReportSystemError(errno,
errno is wrong here - stat() succeeded.  You want to explicitly report
EINVAL.
...
@@ -2582,8 +2648,9 @@ static char *virCgroupIdentifyRoot(virCgroupPtr group)
             return NULL;
         }
-        ignore_value(VIR_STRNDUP_QUIET(ret, group->controllers[i].mountPoint,
-                                       tmp - group->controllers[i].mountPoint));
+        if (VIR_STRNDUP(ret, group->controllers[i].mountPoint,
+                        tmp - group->controllers[i].mountPoint) < 0)
+            return NULL;
         return ret;
You can still use ignore_value() here rather than 'if', if desired,
since ret will be NULL if VIR_STRNDUP fails.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

    