cgroup: distinguish the default and legacy hierarchies when handling cftypes
Until now, cftype arrays carried files for both the default and legacy
hierarchies and the files which needed to be used on only one of them
were flagged with either CFTYPE_ONLY_ON_DFL or CFTYPE_INSANE. This
gets confusing very quickly and we may end up exposing interface files
to the default hierarchy without thinking it through.
This patch makes cgroup core provide separate sets of interfaces for
cftype handling so that the cftypes for the default and legacy
hierarchies are clearly distinguished. The previous two patches
renamed the existing ones so that they clearly indicate that they're
for the legacy hierarchies. This patch adds the interface for the
default hierarchy and apply them selectively depending on the
hierarchy type.
* cftypes added through cgroup_subsys->dfl_cftypes and
cgroup_add_dfl_cftypes() only show up on the default hierarchy.
* cftypes added through cgroup_subsys->legacy_cftypes and
cgroup_add_legacy_cftypes() only show up on the legacy hierarchies.
* cgroup_subsys->dfl_cftypes and ->legacy_cftypes can point to the
same array for the cases where the interface files are identical on
both types of hierarchies.
* This makes all the existing subsystem interface files legacy-only by
default and all subsystems will have no interface file created when
enabled on the default hierarchy. Each subsystem should explicitly
review and compose the interface for the default hierarchy.
* A boot param "cgroup__DEVEL__legacy_files_on_dfl" is added which
makes subsystems which haven't decided the interface files for the
default hierarchy to present the legacy files on the default
hierarchy so that its behavior on the default hierarchy can be
tested. As the awkward name suggests, this is for development only.
* memcg's CFTYPE_INSANE on "use_hierarchy" is noop now as the whole
array isn't used on the default hierarchy. The flag is removed.
v2: Updated documentation for cgroup__DEVEL__legacy_files_on_dfl.
v3: Clear CFTYPE_ONLY_ON_DFL and CFTYPE_INSANE when cfts are removed
as suggested by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c275aa4..374ebdf 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -149,6 +149,12 @@
*/
static bool cgrp_dfl_root_visible;
+/*
+ * Set by the boot param of the same name and makes subsystems with NULL
+ * ->dfl_files to use ->legacy_files on the default hierarchy.
+ */
+static bool cgroup_legacy_files_on_dfl;
+
/* some controllers are not supported in the default hierarchy */
static const unsigned int cgrp_dfl_root_inhibit_ss_mask = 0
#ifdef CONFIG_CGROUP_DEBUG
@@ -3085,6 +3091,9 @@
kfree(cft->kf_ops);
cft->kf_ops = NULL;
cft->ss = NULL;
+
+ /* revert flags set by cgroup core while adding @cfts */
+ cft->flags &= ~(CFTYPE_ONLY_ON_DFL | CFTYPE_INSANE);
}
}
@@ -3195,8 +3204,37 @@
return ret;
}
+/**
+ * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
+ * @ss: target cgroup subsystem
+ * @cfts: zero-length name terminated array of cftypes
+ *
+ * Similar to cgroup_add_cftypes() but the added files are only used for
+ * the default hierarchy.
+ */
+int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
+{
+ struct cftype *cft;
+
+ for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
+ cft->flags |= CFTYPE_ONLY_ON_DFL;
+ return cgroup_add_cftypes(ss, cfts);
+}
+
+/**
+ * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
+ * @ss: target cgroup subsystem
+ * @cfts: zero-length name terminated array of cftypes
+ *
+ * Similar to cgroup_add_cftypes() but the added files are only used for
+ * the legacy hierarchies.
+ */
int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
+ struct cftype *cft;
+
+ for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
+ cft->flags |= CFTYPE_INSANE;
return cgroup_add_cftypes(ss, cfts);
}
@@ -4893,9 +4931,19 @@
* disabled flag and cftype registration needs kmalloc,
* both of which aren't available during early_init.
*/
- if (!ss->disabled) {
- cgrp_dfl_root.subsys_mask |= 1 << ss->id;
- WARN_ON(cgroup_add_cftypes(ss, ss->legacy_cftypes));
+ if (ss->disabled)
+ continue;
+
+ cgrp_dfl_root.subsys_mask |= 1 << ss->id;
+
+ if (cgroup_legacy_files_on_dfl && !ss->dfl_cftypes)
+ ss->dfl_cftypes = ss->legacy_cftypes;
+
+ if (ss->dfl_cftypes == ss->legacy_cftypes) {
+ WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
+ } else {
+ WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
+ WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
}
}
@@ -5291,6 +5339,14 @@
}
__setup("cgroup_disable=", cgroup_disable);
+static int __init cgroup_set_legacy_files_on_dfl(char *str)
+{
+ printk("cgroup: using legacy files on the default hierarchy\n");
+ cgroup_legacy_files_on_dfl = true;
+ return 0;
+}
+__setup("cgroup__DEVEL__legacy_files_on_dfl", cgroup_set_legacy_files_on_dfl);
+
/**
* css_tryget_online_from_dir - get corresponding css from a cgroup dentry
* @dentry: directory dentry of interest