On Thu, Oct 04, 2018 at 02:43:18PM +0200, Fabiano Fidêncio wrote:
> On Tue, 2018-10-02 at 10:43 +0200, Pavel Hrdina wrote:
> > When creating cgroup hierarchy we need to enable controllers in the
> > parent cgroup in order to be usable. That means writing
> > "+{controller}"
> > into cgroup.subtree_control file. We can enable only controllers
> > that
> > are enabled for parent cgroup, that means we need to do that for the
> > whole cgroup tree.
> >
> > Cgroups for threads needs to be handled differently in cgroup
> > v2. There
> > are two types of controllers:
> >
> > - domain controllers: these cannot be enabled for threads
> > - threaded controllers: these can be enabled for threads
> >
> > In addition there are multiple types of cgroups:
> >
> > - domain: normal cgroup
> > - domain threaded: a domain cgroup that serves as root for
> > threaded
> > cgroups
> > - domain invalid: invalid cgroup, can be changed into threaded,
> > this
> > is the default state if you create subgroup
> > inside
> > domain threaded group or threaded group
> > - threaded: threaded cgroup which can have domain threaded or
> > threaded as parent group
> >
> > In order to create threaded cgroup it's sufficient to write
> > "threaded"
> > into cgroup.type file, it will automatically make parent cgroup
> > "domain threaded" if it was only "domain". In case the parent cgroup
> > is already "domain threaded" or "threaded" it will modify only the
> > type
> > of current cgroup. After that we can enable threaded controllers.
> >
> > Signed-off-by: Pavel Hrdina <phrdina@xxxxxxxxxx>
> > ---
> > src/util/vircgroup.c | 2 +-
> > src/util/vircgroupbackend.h | 1 +
> > src/util/vircgroupv2.c | 78
> > +++++++++++++++++++++++++++++++++++++
> > 3 files changed, 80 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/util/vircgroup.c b/src/util/vircgroup.c
> > index 1097b1f998..dc249bfe33 100644
> > --- a/src/util/vircgroup.c
> > +++ b/src/util/vircgroup.c
> > @@ -938,7 +938,7 @@ virCgroupNewThread(virCgroupPtr domain,
> > if (virCgroupNew(-1, name, domain, controllers, group) < 0)
> > return -1;
> >
> > - if (virCgroupMakeGroup(domain, *group, create, VIR_CGROUP_NONE)
> > < 0) {
> > + if (virCgroupMakeGroup(domain, *group, create,
> > VIR_CGROUP_THREAD) < 0) {
> > virCgroupFree(group);
> > return -1;
> > }
> > diff --git a/src/util/vircgroupbackend.h
> > b/src/util/vircgroupbackend.h
> > index b1f19233e4..86d1539e07 100644
> > --- a/src/util/vircgroupbackend.h
> > +++ b/src/util/vircgroupbackend.h
> > @@ -33,6 +33,7 @@ typedef enum {
> > * before creating subcgroups
> > and
> > * attaching tasks
> > */
> > + VIR_CGROUP_THREAD = 1 << 1, /* cgroup v2 handles threads
> > differently */
> > } virCgroupBackendFlags;
> >
> > typedef enum {
> > diff --git a/src/util/vircgroupv2.c b/src/util/vircgroupv2.c
> > index 3ca463e4c2..8fb9ace474 100644
> > --- a/src/util/vircgroupv2.c
> > +++ b/src/util/vircgroupv2.c
> > @@ -336,6 +336,83 @@ virCgroupV2PathOfController(virCgroupPtr group,
> > }
> >
> >
> > +static int
> > +virCgroupV2EnableController(virCgroupPtr parent,
> > + int controller)
> > +{
> > + VIR_AUTOFREE(char *) val = NULL;
> > +
> > + if (virAsprintf(&val, "+%s",
> > + virCgroupV2ControllerTypeToString(controller)) <
> > 0) {
> > + return -1;
> > + }
> > +
> > + if (virCgroupSetValueStr(parent, controller,
> > + "cgroup.subtree_control", val) < 0) {
> > + return -1;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +
> > +static int
> > +virCgroupV2MakeGroup(virCgroupPtr parent ATTRIBUTE_UNUSED,
> > + virCgroupPtr group,
> > + bool create,
> > + unsigned int flags)
> > +{
> > + VIR_AUTOFREE(char *) path = NULL;
> > + int controller;
> > +
> > + VIR_DEBUG("Make group %s", group->path);
> > +
> > + controller = virCgroupV2GetAnyController(group);
> > + if (virCgroupV2PathOfController(group, controller, "", &path) <
> > 0)
> > + return -1;
> > +
> > + VIR_DEBUG("Make controller %s", path);
> > +
> > + if (!virFileExists(path)) {
> > + if (!create || mkdir(path, 0755 || errno == EEXIST) < 0) {
>
> The `mdkir(path, 0755 || errno == EEXIST) < 0` part of the check
> doesn't look right.
Nice catch, I'll fix that, thanks.
Pavel
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