Commit 667c2491 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
parent c29adf24

include/linux/cgroup.h

+7 −1
Original line number Diff line number Diff line
@@ -203,7 +203,13 @@ struct cgroup { 
	struct kernfs_node *kn;		/* cgroup kernfs entry */

	struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */



	/* the bitmask of subsystems enabled on the child cgroups */

	/*

	 * The bitmask of subsystems enabled on the child cgroups.

	 * ->subtree_control is the one configured through

	 * "cgroup.subtree_control" while ->child_subsys_mask is the

	 * effective one which may have more subsystems enabled.

	 */

	unsigned int subtree_control;

	unsigned int child_subsys_mask;



	/* Private pointers for each registered subsystem */

kernel/cgroup.c

+29 −17
Original line number Diff line number Diff line
@@ -1036,6 +1036,11 @@ static void cgroup_put(struct cgroup *cgrp) 
	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 @@ static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask) 
		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 @@ static int cgroup_controllers_show(struct seq_file *seq, void *v) 
{

	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 @@ static int cgroup_subtree_control_show(struct seq_file *seq, void *v) 
{

	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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 


	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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 
			/* 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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 
				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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 
	}



	/*

	 * 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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 
		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 @@ out_unlock: 
	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 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, 


	/*

	 * 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);

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