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cgroup: restructure child_subsys_mask handling in cgroup_subtree_control_write()

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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: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2014-11-18 02:49:50 -05:00
parent 0f060deb5c
commit 755bf5ee86
1 changed files with 12 additions and 12 deletions
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24
kernel/cgroup.c
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@ -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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
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)))