[libvirt] [PATCH] cgroup: Fix start VMs coincidently failed

[Michal Privoznik]

On 20.03.2014 08:24, Wangyufei (James) wrote:
>>From 0163328efa67da1d63e504c86e323db5affa378f Mon Sep 17 00:00:00 2001
> From: Wang Yufei <james.wangyufei at huawei.com>
> Date: Thu, 20 Mar 2014 07:14:01 +0000
> Subject: [PATCH] cgroup: Fix start VMs coincidently failed
> When I start multi VMs coincidently and any of the cgroup directories
> named machine doesn't exist. There's a chance that VM start failed because
> of creating directory failed:
> Unable to initialize /machine cgroup: File exists
> When the errno returned by mkdir in virCgroupMakeGroup is EEXIST,
> we should pass it through and continue to start the VM.
> Signed-off-by: Wang Yufei <james.wangyufei at huawei.com>
> ---
>   src/util/vircgroup.c | 4 ++++
>   1 file changed, 4 insertions(+)
> diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
> index c5925b1..a10d6f6 100644
> --- a/src/util/vircgroup.c
> +++ b/src/util/vircgroup.c
> @@ -924,6 +924,10 @@ virCgroupMakeGroup(virCgroupPtr parent,
>           if (!virFileExists(path)) {
>               if (!create ||
>                   mkdir(path, 0755) < 0) {
> +                if (errno == EEXIST) {
> +                    VIR_FREE(path);
> +                    continue;
> +                }
>                   /* With a kernel that doesn't support multi-level directory
>                    * for blkio controller, libvirt will fail and disable all
>                    * other controllers even though they are available. So
>

NACK. Prior to starting a domain we make sure that no historical cgroup 
is lying around. So if we don't remove the cgroup there that's the 
actual bug and this just shadows it. We can't guarantee anything if the 
old cgroup is not removed and the new one is created by us. However, we 
are not removing the stale cgroup in case of LXC only in QEMU. Is it LXC 
that you are seeing this error on?

Michal