From 41b2cee2a8946c3ee293ca04ed60f7e2817936b9 Mon Sep 17 00:00:00 2001
From: Lai Jiangshan <laijs@cn.fujitsu.com>
Date: Fri, 29 Oct 2010 17:32:16 +0800
Subject: [PATCH] qemu_driver: add virCgroupMounted

When we mount any cgroup without "-o devices", we will fail to start vms:

error: Failed to start domain vm1
error: Unable to deny all devices for vm1: No such file or directory

When we mount any cgroup without "-o cpu", we will fail to get schedinfo:
Scheduler      : posix
error: unable to get cpu shares tunable: No such file or directory

We should only use the cgroup controllers which are mounted on host.
So I add virCgroupMounted() for qemuCgroupControllerActive()

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 src/libvirt_private.syms |  1 +
 src/qemu/qemu_driver.c   |  2 ++
 src/util/cgroup.c        | 13 +++++++++++++
 src/util/cgroup.h        |  1 +
 4 files changed, 17 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index cf06256ccd..cf64bd3661 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -72,6 +72,7 @@ virCgroupGetMemoryHardLimit;
 virCgroupGetMemorySoftLimit;
 virCgroupGetMemoryUsage;
 virCgroupGetSwapHardLimit;
+virCgroupMounted;
 virCgroupRemove;
 virCgroupSetCpuShares;
 virCgroupSetFreezerState;
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 1eea3a989f..554bf86281 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -730,6 +730,8 @@ static int qemuCgroupControllerActive(struct qemud_driver *driver,
 {
     if (driver->cgroup == NULL)
         return 0;
+    if (!virCgroupMounted(driver->cgroup, controller))
+        return 0;
     if (driver->cgroupControllers & (1 << controller))
         return 1;
     return 0;
diff --git a/src/util/cgroup.c b/src/util/cgroup.c
index 7e887dc55c..3779f76241 100644
--- a/src/util/cgroup.c
+++ b/src/util/cgroup.c
@@ -71,6 +71,19 @@ void virCgroupFree(virCgroupPtr *group)
     VIR_FREE(*group);
 }
 
+/**
+ * virCgroupMounted: query whether a cgroup subsystem is mounted or not
+ *
+ * @cgroup: The group structure to be queried
+ * @controller: cgroup subsystem id
+ *
+ * Returns true if a cgroup is subsystem is mounted.
+ */
+bool virCgroupMounted(virCgroupPtr cgroup, int controller)
+{
+    return cgroup->controllers[controller].mountPoint != NULL;
+}
+
 #if defined HAVE_MNTENT_H && defined HAVE_GETMNTENT_R
 /*
  * Process /proc/mounts figuring out what controllers are
diff --git a/src/util/cgroup.h b/src/util/cgroup.h
index b8f2d0899b..9e1c61fca5 100644
--- a/src/util/cgroup.h
+++ b/src/util/cgroup.h
@@ -83,5 +83,6 @@ int virCgroupGetFreezerState(virCgroupPtr group, char **state);
 int virCgroupRemove(virCgroupPtr group);
 
 void virCgroupFree(virCgroupPtr *group);
+bool virCgroupMounted(virCgroupPtr cgroup, int controller);
 
 #endif /* CGROUP_H */
-- 
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