Commit 755bf5ee authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: restructure child_subsys_mask handling in cgroup_subtree_control_write() 



Make cgroup_subtree_control_write() first calculate new
subtree_control (new_sc), child_subsys_mask (new_ss) and
css_enable/disable masks before applying them to the cgroup.  Also,
store the original subtree_control (old_sc) and child_subsys_mask
(old_ss) and use them to restore the orignal state after failure.

This patch shouldn't cause any behavior changes.  This prepares for a
fix for a bug in the async css offline wait logic.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarZefan Li <lizefan@huawei.com>
parent 0f060deb

kernel/cgroup.c

+12 −12
Original line number Diff line number Diff line
@@ -2653,7 +2653,7 @@ 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;

	unsigned int css_enable, css_disable, old_sc, new_sc, old_ss, new_ss;

	struct cgroup *cgrp, *child;

	struct cgroup_subsys *ss;

	char *tok;
@@ -2770,18 +2770,19 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, 
	 * subsystems than specified may need to be enabled or disabled

	 * depending on subsystem dependencies.

	 */

	cgrp->subtree_control |= enable;

	cgrp->subtree_control &= ~disable;

	old_sc = cgrp->subtree_control;

	old_ss = cgrp->child_subsys_mask;

	new_sc = (old_sc | enable) & ~disable;

	new_ss = cgroup_calc_child_subsys_mask(cgrp, new_sc);



	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;

	css_enable = ~old_ss & new_ss;

	css_disable = old_ss & ~new_ss;

	enable |= css_enable;

	disable |= css_disable;



	cgrp->subtree_control = new_sc;

	cgrp->child_subsys_mask = new_ss;



	/*

	 * Create new csses or make the existing ones visible.  A css is

	 * created invisible if it's being implicitly enabled through
@@ -2844,9 +2845,8 @@ out_unlock: 
	return ret ?: nbytes;



err_undo_css:

	cgrp->subtree_control &= ~enable;

	cgrp->subtree_control |= disable;

	cgroup_refresh_child_subsys_mask(cgrp);

	cgrp->subtree_control = old_sc;

	cgrp->child_subsys_mask = old_ss;



	for_each_subsys(ss, ssid) {

		if (!(enable & (1 << ssid)))

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