[libvirt] [PATCH 1/3] vircgroup: fix cgroups v2 controllers detection

[Pavel Hrdina]

When creating new group for cgroups v2 the we cannot check
cgroups.controllers for that cgroup because the directory is created
later.  In that case we should check cgroups.subtree_control of parent
group to get list of controllers enabled for child cgroups.

In order to achieve that we will prefer the parent group if it exists,
the current group will be used only for root group.

Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
---
 src/util/vircgroup.c        |  2 +-
 src/util/vircgroupbackend.h |  3 ++-
 src/util/vircgroupv1.c      |  3 ++-
 src/util/vircgroupv2.c      | 23 ++++++++++++++++-------
 4 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
index f7afc2964d..cc21758323 100644
--- a/src/util/vircgroup.c
+++ b/src/util/vircgroup.c
@@ -407,7 +407,7 @@ virCgroupDetect(virCgroupPtr group,
 
     for (i = 0; i < VIR_CGROUP_BACKEND_TYPE_LAST; i++) {
         if (group->backends[i]) {
-            int rc = group->backends[i]->detectControllers(group, controllers);
+            int rc = group->backends[i]->detectControllers(group, controllers, parent);
             if (rc < 0)
                 return -1;
             controllersAvailable |= rc;
diff --git a/src/util/vircgroupbackend.h b/src/util/vircgroupbackend.h
index a91719f89d..77451b0cb6 100644
--- a/src/util/vircgroupbackend.h
+++ b/src/util/vircgroupbackend.h
@@ -98,7 +98,8 @@ typedef char *
 
 typedef int
 (*virCgroupDetectControllersCB)(virCgroupPtr group,
-                                int controllers);
+                                int controllers,
+                                virCgroupPtr parent);
 
 typedef bool
 (*virCgroupHasControllerCB)(virCgroupPtr cgroup,
diff --git a/src/util/vircgroupv1.c b/src/util/vircgroupv1.c
index 7968ab3cf0..4231d8d6fa 100644
--- a/src/util/vircgroupv1.c
+++ b/src/util/vircgroupv1.c
@@ -420,7 +420,8 @@ virCgroupV1StealPlacement(virCgroupPtr group)
 
 static int
 virCgroupV1DetectControllers(virCgroupPtr group,
-                             int controllers)
+                             int controllers,
+                             virCgroupPtr parent ATTRIBUTE_UNUSED)
 {
     size_t i;
     size_t j;
diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c
index 9d8a38925a..9c44b3473e 100644
--- a/src/util/vircgroupv2.c
+++ b/src/util/vircgroupv2.c
@@ -242,7 +242,8 @@ virCgroupV2StealPlacement(virCgroupPtr group)
 
 
 static int
-virCgroupV2ParseControllersFile(virCgroupPtr group)
+virCgroupV2ParseControllersFile(virCgroupPtr group,
+                                virCgroupPtr parent)
 {
     int rc;
     VIR_AUTOFREE(char *) contStr = NULL;
@@ -250,10 +251,17 @@ virCgroupV2ParseControllersFile(virCgroupPtr group)
     char **contList = NULL;
     char **tmp;
 
-    if (virAsprintf(&contFile, "%s%s/cgroup.controllers",
-                    group->unified.mountPoint,
-                    NULLSTR_EMPTY(group->unified.placement)) < 0)
-        return -1;
+    if (parent) {
+        if (virAsprintf(&contFile, "%s%s/cgroup.subtree_control",
+                        parent->unified.mountPoint,
+                        NULLSTR_EMPTY(parent->unified.placement)) < 0)
+            return -1;
+    } else {
+        if (virAsprintf(&contFile, "%s%s/cgroup.controllers",
+                        group->unified.mountPoint,
+                        NULLSTR_EMPTY(group->unified.placement)) < 0)
+            return -1;
+    }
 
     rc = virFileReadAll(contFile, 1024 * 1024, &contStr);
     if (rc < 0) {
@@ -286,11 +294,12 @@ virCgroupV2ParseControllersFile(virCgroupPtr group)
 
 static int
 virCgroupV2DetectControllers(virCgroupPtr group,
-                             int controllers)
+                             int controllers,
+                             virCgroupPtr parent)
 {
     size_t i;
 
-    if (virCgroupV2ParseControllersFile(group) < 0)
+    if (virCgroupV2ParseControllersFile(group, parent) < 0)
         return -1;
 
     /* In cgroup v2 there is no cpuacct controller, the cpu.stat file always
-- 
2.21.0