Commit 12b3bb6a authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: factor out cgroup_apply_control_disable() from cgroup_subtree_control_write() 



Factor out css disabling and hiding into cgroup_apply_control_disable().

* Nest subsystem walk inside child walk.  The child walk will later be
  converted to subtree walk which is a bit more expensive.

* Instead of operating on the differential masks @css_enable and
  @css_disable, simply disable or hide csses according to the current
  cgroup_control() and cgroup_ss_mask().  This leads to the same
  result and is simpler and more robust.

* This allows error handling path to share the same code.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarZefan Li <lizefan@huawei.com>
parent 1b9b96a1

kernel/cgroup.c

+41 −33
Original line number Diff line number Diff line
@@ -3012,6 +3012,43 @@ static bool cgroup_drain_offline(struct cgroup *cgrp) 
	return false;

}



/**

 * cgroup_apply_control_disable - kill or hide csses according to control

 * @cgrp: parent of the target cgroups

 *

 * Walk @cgrp's children and kill and hide csses so that they match

 * cgroup_ss_mask() and cgroup_visible_mask().

 *

 * A css is hidden when the userland requests it to be disabled while other

 * subsystems are still depending on it.  The css must not actively control

 * resources and be in the vanilla state if it's made visible again later.

 * Controllers which may be depended upon should provide ->css_reset() for

 * this purpose.

 */

static void cgroup_apply_control_disable(struct cgroup *cgrp)

{

	struct cgroup *dsct;

	struct cgroup_subsys *ss;

	int ssid;



	cgroup_for_each_live_child(dsct, cgrp) {

		for_each_subsys(ss, ssid) {

			struct cgroup_subsys_state *css = cgroup_css(dsct, ss);



			if (!css)

				continue;



			if (!(cgroup_ss_mask(dsct) & (1 << ss->id))) {

				kill_css(css);

			} else if (!(cgroup_control(dsct) & (1 << ss->id))) {

				css_clear_dir(css, NULL);

				if (ss->css_reset)

					ss->css_reset(css);

			}

		}

	}

}



/* change the enabled child controllers for a cgroup in the default hierarchy */

static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,

					    char *buf, size_t nbytes,
@@ -3160,27 +3197,8 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 
	if (ret)

		goto err_undo_css;



	/*

	 * 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.  The

	 * css must not actively control resources and be in the vanilla

	 * state if it's made visible again later.  Controllers which may

	 * be depended upon should provide ->css_reset() for this purpose.

	 */

	do_each_subsys_mask(ss, ssid, disable) {

		cgroup_for_each_live_child(child, cgrp) {

			struct cgroup_subsys_state *css = cgroup_css(child, ss);



			if (css_disable & (1 << ssid)) {

				kill_css(css);

			} else {

				css_clear_dir(css, NULL);

				if (ss->css_reset)

					ss->css_reset(css);

			}

		}

	} while_each_subsys_mask();

	/* all tasks are migrated out of disabled csses, commit disable */

	cgroup_apply_control_disable(cgrp);



	kernfs_activate(cgrp->kn);

	ret = 0;
@@ -3189,22 +3207,12 @@ out_unlock: 
	return ret ?: nbytes;



err_undo_css:

	/* restore masks and shoot down new csses */

	cgrp->subtree_control = old_sc;

	cgrp->subtree_ss_mask = old_ss;



	do_each_subsys_mask(ss, ssid, enable) {

		cgroup_for_each_live_child(child, cgrp) {

			struct cgroup_subsys_state *css = cgroup_css(child, ss);



			if (!css)

				continue;

	cgroup_apply_control_disable(cgrp);



			if (css_enable & (1 << ssid))

				kill_css(css);

			else

				css_clear_dir(css, NULL);

		}

	} while_each_subsys_mask();

	goto out_unlock;

}

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