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cgroup: factor out cgroup_apply_control_disable() from cgroup_subtree_control_write()

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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: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2016-03-03 09:57:59 -05:00
parent 1b9b96a12b
commit 12b3bb6af8
1 changed files with 41 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

74
kernel/cgroup.c
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@ -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 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
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);
cgroup_apply_control_disable(cgrp);
if (!css)
continue;
if (css_enable & (1 << ssid))
kill_css(css);
else
css_clear_dir(css, NULL);
}
} while_each_subsys_mask();
goto out_unlock;
}