This patch add a new debug control file on the cgroup v2 root directory
to print out the cgroup hierarchy for each of the v2 controllers.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
kernel/cgroup/debug.c | 141 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 141 insertions(+)
diff --git a/kernel/cgroup/debug.c b/kernel/cgroup/debug.c
index a2dbf77..3adb26a 100644
--- a/kernel/cgroup/debug.c
+++ b/kernel/cgroup/debug.c
@@ -268,6 +268,141 @@ static int cgroup_masks_read(struct seq_file *seq, void *v)
return 0;
}
+/*
+ * Print out all the child cgroup names that doesn't have a css for the
+ * corresponding cgroup_subsys. If a child cgroup has a css, put that into
+ * the given cglist to be processed in the next iteration.
+ */
+#define CGLIST_MAX 16
+static void print_hierarchy(struct seq_file *seq,
+ struct cgroup *cgrp,
+ struct cgroup_subsys *ss,
+ struct cgroup_subsys_state *css,
+ struct cgroup **cglist,
+ int *cgcnt)
+{
+ struct cgroup *child;
+ struct cgroup_subsys_state *child_css;
+ char cgname[64];
+
+ cgname[sizeof(cgname) - 1] = '\0';
+ /*
+ * Iterate all live children of the given cgroup.
+ */
+ list_for_each_entry(child, &cgrp->self.children, self.sibling) {
+ if (cgroup_is_dead(child))
+ continue;
+
+ child_css = rcu_dereference_check(child->subsys[ss->id], true);
+ if (child_css) {
+ WARN_ON(child_css->parent != css);
+ if (*cgcnt < CGLIST_MAX) {
+ cglist[*cgcnt] = child;
+ (*cgcnt)++;
+ }
+ continue;
+ }
+
+ /*
+ * Skip resource domain cgroup
+ */
+ if (test_bit(CGRP_RESOURCE_DOMAIN, &child->flags))
+ continue;
+
+ cgroup_name(child, cgname, sizeof(cgname)-1);
+ seq_putc(seq, ',');
+ seq_puts(seq, cgname);
+ print_hierarchy(seq, child, ss, css, cglist, cgcnt);
+ }
+}
+
+/*
+ * Print the hierachies with respect to each controller for the default
+ * hierarchy.
+ *
+ * Each child level is printed on a separate line. Set of cgroups that
+ * have the same css will be grouped together and separated by comma.
+ * Process in those cgroups will be in the same node (css) in the
+ * controller's hierarchy. There is an exception that for resource
+ * domain cgroup, the processes associated with its parent and its
+ * affiliates will be mapped to the css of that resource domain cgroup
+ * instead.
+ *
+ * If there are more than CGLIST_MAX sets of cgroups in each level,
+ * the extra ones will be skipped.
+ */
+static int controller_hierachies_read(struct seq_file *seq, void *v)
+{
+ struct cgroup *root = seq_css(seq)->cgroup;
+ struct cgroup_subsys *ss;
+ struct cgroup_subsys_state *css;
+ struct cgroup *cgrp;
+ struct cgroup *cglist[CGLIST_MAX];
+ struct cgroup *cg2list[CGLIST_MAX];
+ int i, idx, cgnum, cg2num;
+ char cgname[64];
+
+ cgname[sizeof(cgname) - 1] = '\0';
+ mutex_lock(&cgroup_mutex);
+ for_each_subsys(ss, i) {
+ if (!(root->root->subsys_mask & (1 << ss->id)))
+ continue;
+ seq_puts(seq, ss->name);
+ seq_puts(seq, ":\n");
+
+ cgnum = 1;
+ cg2num = 0;
+ cglist[0] = root;
+ idx = 0;
+ while (cgnum) {
+ if (idx)
+ seq_putc(seq, ' ');
+ cgrp = cglist[idx];
+ if (test_bit(CGRP_RESOURCE_DOMAIN, &cgrp->flags)) {
+ struct cgroup *parent;
+
+ parent = container_of(cgrp->self.parent,
+ struct cgroup, self);
+ cgroup_name(parent, cgname, sizeof(cgname)-1);
+ seq_printf(seq, "%s.rd", cgname);
+ } else {
+ cgroup_name(cgrp, cgname, sizeof(cgname)-1);
+ seq_puts(seq, cgname);
+ }
+ css = rcu_dereference_check(cgrp->subsys[ss->id], true);
+ WARN_ON(!css);
+
+ if (cgrp == root)
+ seq_printf(seq, "[%d]", css->id);
+ else
+ seq_printf(seq, "[%d:P=%d]", css->id,
+ css->parent->id);
+
+ /*
+ * List all the cgroups that use the current
+ * css.
+ */
+ print_hierarchy(seq, cgrp, ss, css, cg2list, &cg2num);
+
+ if (++idx < cgnum)
+ continue;
+
+ /*
+ * Move cg2list to cglist.
+ */
+ cgnum = cg2num;
+ idx = cg2num = 0;
+ if (cgnum)
+ memcpy(cglist, cg2list,
+ cgnum * sizeof(cglist[0]));
+ seq_putc(seq, '\n');
+ }
+ seq_putc(seq, '\n');
+ }
+ mutex_unlock(&cgroup_mutex);
+ return 0;
+}
+
static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
{
return (!cgroup_is_populated(css->cgroup) &&
@@ -314,6 +449,12 @@ static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
},
{
+ .name = "controller_hierachies",
+ .seq_show = controller_hierachies_read,
+ .flags = CFTYPE_ONLY_ON_ROOT|__CFTYPE_ONLY_ON_DFL,
+ },
+
+ {
.name = "releasable",
.read_u64 = releasable_read,
},
--
1.8.3.1
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