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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>
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@ -203,7 +203,13 @@ struct cgroup {
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struct kernfs_node *kn; /* cgroup kernfs entry */
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struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */
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/* the bitmask of subsystems enabled on the child cgroups */
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/*
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* The bitmask of subsystems enabled on the child cgroups.
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* ->subtree_control is the one configured through
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* "cgroup.subtree_control" while ->child_subsys_mask is the
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* effective one which may have more subsystems enabled.
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*/
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unsigned int subtree_control;
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unsigned int child_subsys_mask;
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/* Private pointers for each registered subsystem */
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@ -1036,6 +1036,11 @@ static void cgroup_put(struct cgroup *cgrp)
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css_put(&cgrp->self);
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}
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static void cgroup_refresh_child_subsys_mask(struct cgroup *cgrp)
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{
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cgrp->child_subsys_mask = cgrp->subtree_control;
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}
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/**
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* cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
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* @kn: the kernfs_node being serviced
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@ -1208,12 +1213,15 @@ static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask)
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up_write(&css_set_rwsem);
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src_root->subsys_mask &= ~(1 << ssid);
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src_root->cgrp.child_subsys_mask &= ~(1 << ssid);
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src_root->cgrp.subtree_control &= ~(1 << ssid);
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cgroup_refresh_child_subsys_mask(&src_root->cgrp);
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/* default hierarchy doesn't enable controllers by default */
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dst_root->subsys_mask |= 1 << ssid;
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if (dst_root != &cgrp_dfl_root)
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dst_root->cgrp.child_subsys_mask |= 1 << ssid;
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if (dst_root != &cgrp_dfl_root) {
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dst_root->cgrp.subtree_control |= 1 << ssid;
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cgroup_refresh_child_subsys_mask(&dst_root->cgrp);
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}
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if (ss->bind)
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ss->bind(css);
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@ -2454,7 +2462,7 @@ static int cgroup_controllers_show(struct seq_file *seq, void *v)
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{
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struct cgroup *cgrp = seq_css(seq)->cgroup;
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cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->child_subsys_mask);
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cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->subtree_control);
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return 0;
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}
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@ -2463,7 +2471,7 @@ static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
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{
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struct cgroup *cgrp = seq_css(seq)->cgroup;
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cgroup_print_ss_mask(seq, cgrp->child_subsys_mask);
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cgroup_print_ss_mask(seq, cgrp->subtree_control);
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return 0;
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}
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@ -2608,7 +2616,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
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for_each_subsys(ss, ssid) {
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if (enable & (1 << ssid)) {
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if (cgrp->child_subsys_mask & (1 << ssid)) {
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if (cgrp->subtree_control & (1 << ssid)) {
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enable &= ~(1 << ssid);
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continue;
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}
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@ -2616,7 +2624,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
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/* unavailable or not enabled on the parent? */
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if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
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(cgroup_parent(cgrp) &&
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!(cgroup_parent(cgrp)->child_subsys_mask & (1 << ssid)))) {
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!(cgroup_parent(cgrp)->subtree_control & (1 << ssid)))) {
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ret = -ENOENT;
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goto out_unlock;
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}
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@ -2644,14 +2652,14 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
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return restart_syscall();
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}
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} else if (disable & (1 << ssid)) {
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if (!(cgrp->child_subsys_mask & (1 << ssid))) {
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if (!(cgrp->subtree_control & (1 << ssid))) {
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disable &= ~(1 << ssid);
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continue;
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}
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/* a child has it enabled? */
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cgroup_for_each_live_child(child, cgrp) {
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if (child->child_subsys_mask & (1 << ssid)) {
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if (child->subtree_control & (1 << ssid)) {
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ret = -EBUSY;
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goto out_unlock;
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}
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@ -2665,7 +2673,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
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}
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/*
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* Except for the root, child_subsys_mask must be zero for a cgroup
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* Except for the root, subtree_control must be zero for a cgroup
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* with tasks so that child cgroups don't compete against tasks.
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*/
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if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) {
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@ -2673,8 +2681,9 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
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goto out_unlock;
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}
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cgrp->child_subsys_mask |= enable;
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cgrp->child_subsys_mask &= ~disable;
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cgrp->subtree_control |= enable;
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cgrp->subtree_control &= ~disable;
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cgroup_refresh_child_subsys_mask(cgrp);
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/* create new csses */
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for_each_subsys(ss, ssid) {
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@ -2713,8 +2722,9 @@ out_unlock:
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return ret ?: nbytes;
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err_undo_css:
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cgrp->child_subsys_mask &= ~enable;
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cgrp->child_subsys_mask |= disable;
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cgrp->subtree_control &= ~enable;
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cgrp->subtree_control |= disable;
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cgroup_refresh_child_subsys_mask(cgrp);
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for_each_subsys(ss, ssid) {
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if (!(enable & (1 << ssid)))
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@ -4428,10 +4438,12 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
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/*
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* On the default hierarchy, a child doesn't automatically inherit
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* child_subsys_mask from the parent. Each is configured manually.
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* subtree_control from the parent. Each is configured manually.
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*/
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if (!cgroup_on_dfl(cgrp))
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cgrp->child_subsys_mask = parent->child_subsys_mask;
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if (!cgroup_on_dfl(cgrp)) {
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cgrp->subtree_control = parent->subtree_control;
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cgroup_refresh_child_subsys_mask(cgrp);
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}
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kernfs_activate(kn);
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