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-rw-r--r--include/linux/cgroup.h2
-rw-r--r--kernel/cgroup.c78
2 files changed, 66 insertions, 14 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 8d52c8e..5287f93 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -208,6 +208,8 @@ struct cgroup {
* ->subtree_control is the one configured through
* "cgroup.subtree_control" while ->child_subsys_mask is the
* effective one which may have more subsystems enabled.
+ * Controller knobs are made available iff it's enabled in
+ * ->subtree_control.
*/
unsigned int subtree_control;
unsigned int child_subsys_mask;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 14a9d88..331fa296 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -186,7 +186,8 @@ static void cgroup_put(struct cgroup *cgrp);
static int rebind_subsystems(struct cgroup_root *dst_root,
unsigned int ss_mask);
static int cgroup_destroy_locked(struct cgroup *cgrp);
-static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss);
+static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
+ bool visible);
static void css_release(struct percpu_ref *ref);
static void kill_css(struct cgroup_subsys_state *css);
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
@@ -2577,6 +2578,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
loff_t off)
{
unsigned int enable = 0, disable = 0;
+ unsigned int css_enable, css_disable, old_ctrl, new_ctrl;
struct cgroup *cgrp, *child;
struct cgroup_subsys *ss;
char *tok;
@@ -2630,6 +2632,13 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
}
/*
+ * @ss is already enabled through dependency and
+ * we'll just make it visible. Skip draining.
+ */
+ if (cgrp->child_subsys_mask & (1 << ssid))
+ continue;
+
+ /*
* Because css offlining is asynchronous, userland
* might try to re-enable the same controller while
* the previous instance is still around. In such
@@ -2681,17 +2690,39 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
goto out_unlock;
}
+ /*
+ * Update subsys masks and calculate what needs to be done. More
+ * subsystems than specified may need to be enabled or disabled
+ * depending on subsystem dependencies.
+ */
cgrp->subtree_control |= enable;
cgrp->subtree_control &= ~disable;
+
+ old_ctrl = cgrp->child_subsys_mask;
cgroup_refresh_child_subsys_mask(cgrp);
+ new_ctrl = cgrp->child_subsys_mask;
+
+ css_enable = ~old_ctrl & new_ctrl;
+ css_disable = old_ctrl & ~new_ctrl;
+ enable |= css_enable;
+ disable |= css_disable;
- /* create new csses */
+ /*
+ * Create new csses or make the existing ones visible. A css is
+ * created invisible if it's being implicitly enabled through
+ * dependency. An invisible css is made visible when the userland
+ * explicitly enables it.
+ */
for_each_subsys(ss, ssid) {
if (!(enable & (1 << ssid)))
continue;
cgroup_for_each_live_child(child, cgrp) {
- ret = create_css(child, ss);
+ if (css_enable & (1 << ssid))
+ ret = create_css(child, ss,
+ cgrp->subtree_control & (1 << ssid));
+ else
+ ret = cgroup_populate_dir(child, 1 << ssid);
if (ret)
goto err_undo_css;
}
@@ -2706,13 +2737,21 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
if (ret)
goto err_undo_css;
- /* all tasks are now migrated away from the old csses, kill them */
+ /*
+ * All tasks are migrated out of disabled csses. Kill or hide
+ * them. A css is hidden when the userland requests it to be
+ * disabled while other subsystems are still depending on it.
+ */
for_each_subsys(ss, ssid) {
if (!(disable & (1 << ssid)))
continue;
- cgroup_for_each_live_child(child, cgrp)
- kill_css(cgroup_css(child, ss));
+ cgroup_for_each_live_child(child, cgrp) {
+ if (css_disable & (1 << ssid))
+ kill_css(cgroup_css(child, ss));
+ else
+ cgroup_clear_dir(child, 1 << ssid);
+ }
}
kernfs_activate(cgrp->kn);
@@ -2732,8 +2771,14 @@ err_undo_css:
cgroup_for_each_live_child(child, cgrp) {
struct cgroup_subsys_state *css = cgroup_css(child, ss);
- if (css)
+
+ if (!css)
+ continue;
+
+ if (css_enable & (1 << ssid))
kill_css(css);
+ else
+ cgroup_clear_dir(child, 1 << ssid);
}
}
goto out_unlock;
@@ -4282,12 +4327,14 @@ static void offline_css(struct cgroup_subsys_state *css)
* create_css - create a cgroup_subsys_state
* @cgrp: the cgroup new css will be associated with
* @ss: the subsys of new css
+ * @visible: whether to create control knobs for the new css or not
*
* Create a new css associated with @cgrp - @ss pair. On success, the new
- * css is online and installed in @cgrp with all interface files created.
- * Returns 0 on success, -errno on failure.
+ * css is online and installed in @cgrp with all interface files created if
+ * @visible. Returns 0 on success, -errno on failure.
*/
-static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
+static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss,
+ bool visible)
{
struct cgroup *parent = cgroup_parent(cgrp);
struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
@@ -4311,9 +4358,11 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
goto err_free_percpu_ref;
css->id = err;
- err = cgroup_populate_dir(cgrp, 1 << ss->id);
- if (err)
- goto err_free_id;
+ if (visible) {
+ err = cgroup_populate_dir(cgrp, 1 << ss->id);
+ if (err)
+ goto err_free_id;
+ }
/* @css is ready to be brought online now, make it visible */
list_add_tail_rcu(&css->sibling, &parent_css->children);
@@ -4430,7 +4479,8 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
/* let's create and online css's */
for_each_subsys(ss, ssid) {
if (parent->child_subsys_mask & (1 << ssid)) {
- ret = create_css(cgrp, ss);
+ ret = create_css(cgrp, ss,
+ parent->subtree_control & (1 << ssid));
if (ret)
goto out_destroy;
}
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