cgroup: introduce cgroup->subtree_control
cgroup is implementing support for subsystem dependency which would
require a way to enable a subsystem even when it's not directly
configured through "cgroup.subtree_control".
Previously, cgroup->child_subsys_mask directly reflected
"cgroup.subtree_control" and the enabled subsystems in the child
cgroups. This patch adds cgroup->subtree_control which
"cgroup.subtree_control" operates on. cgroup->child_subsys_mask is
now calculated from cgroup->subtree_control by
cgroup_refresh_child_subsys_mask(), which sets it identical to
cgroup->subtree_control for now.
This will allow using cgroup->child_subsys_mask for all the enabled
subsystems including the implicit ones and ->subtree_control for
tracking the explicitly requested ones. This patch keeps the two
masks identical and doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a46d7e2..14a9d88 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1036,6 +1036,11 @@
css_put(&cgrp->self);
}
+static void cgroup_refresh_child_subsys_mask(struct cgroup *cgrp)
+{
+ cgrp->child_subsys_mask = cgrp->subtree_control;
+}
+
/**
* cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
* @kn: the kernfs_node being serviced
@@ -1208,12 +1213,15 @@
up_write(&css_set_rwsem);
src_root->subsys_mask &= ~(1 << ssid);
- src_root->cgrp.child_subsys_mask &= ~(1 << ssid);
+ src_root->cgrp.subtree_control &= ~(1 << ssid);
+ cgroup_refresh_child_subsys_mask(&src_root->cgrp);
/* default hierarchy doesn't enable controllers by default */
dst_root->subsys_mask |= 1 << ssid;
- if (dst_root != &cgrp_dfl_root)
- dst_root->cgrp.child_subsys_mask |= 1 << ssid;
+ if (dst_root != &cgrp_dfl_root) {
+ dst_root->cgrp.subtree_control |= 1 << ssid;
+ cgroup_refresh_child_subsys_mask(&dst_root->cgrp);
+ }
if (ss->bind)
ss->bind(css);
@@ -2454,7 +2462,7 @@
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
- cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->child_subsys_mask);
+ cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->subtree_control);
return 0;
}
@@ -2463,7 +2471,7 @@
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
- cgroup_print_ss_mask(seq, cgrp->child_subsys_mask);
+ cgroup_print_ss_mask(seq, cgrp->subtree_control);
return 0;
}
@@ -2608,7 +2616,7 @@
for_each_subsys(ss, ssid) {
if (enable & (1 << ssid)) {
- if (cgrp->child_subsys_mask & (1 << ssid)) {
+ if (cgrp->subtree_control & (1 << ssid)) {
enable &= ~(1 << ssid);
continue;
}
@@ -2616,7 +2624,7 @@
/* unavailable or not enabled on the parent? */
if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
(cgroup_parent(cgrp) &&
- !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ssid)))) {
+ !(cgroup_parent(cgrp)->subtree_control & (1 << ssid)))) {
ret = -ENOENT;
goto out_unlock;
}
@@ -2644,14 +2652,14 @@
return restart_syscall();
}
} else if (disable & (1 << ssid)) {
- if (!(cgrp->child_subsys_mask & (1 << ssid))) {
+ if (!(cgrp->subtree_control & (1 << ssid))) {
disable &= ~(1 << ssid);
continue;
}
/* a child has it enabled? */
cgroup_for_each_live_child(child, cgrp) {
- if (child->child_subsys_mask & (1 << ssid)) {
+ if (child->subtree_control & (1 << ssid)) {
ret = -EBUSY;
goto out_unlock;
}
@@ -2665,7 +2673,7 @@
}
/*
- * Except for the root, child_subsys_mask must be zero for a cgroup
+ * Except for the root, subtree_control must be zero for a cgroup
* with tasks so that child cgroups don't compete against tasks.
*/
if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) {
@@ -2673,8 +2681,9 @@
goto out_unlock;
}
- cgrp->child_subsys_mask |= enable;
- cgrp->child_subsys_mask &= ~disable;
+ cgrp->subtree_control |= enable;
+ cgrp->subtree_control &= ~disable;
+ cgroup_refresh_child_subsys_mask(cgrp);
/* create new csses */
for_each_subsys(ss, ssid) {
@@ -2713,8 +2722,9 @@
return ret ?: nbytes;
err_undo_css:
- cgrp->child_subsys_mask &= ~enable;
- cgrp->child_subsys_mask |= disable;
+ cgrp->subtree_control &= ~enable;
+ cgrp->subtree_control |= disable;
+ cgroup_refresh_child_subsys_mask(cgrp);
for_each_subsys(ss, ssid) {
if (!(enable & (1 << ssid)))
@@ -4428,10 +4438,12 @@
/*
* On the default hierarchy, a child doesn't automatically inherit
- * child_subsys_mask from the parent. Each is configured manually.
+ * subtree_control from the parent. Each is configured manually.
*/
- if (!cgroup_on_dfl(cgrp))
- cgrp->child_subsys_mask = parent->child_subsys_mask;
+ if (!cgroup_on_dfl(cgrp)) {
+ cgrp->subtree_control = parent->subtree_control;
+ cgroup_refresh_child_subsys_mask(cgrp);
+ }
kernfs_activate(kn);