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cgroup: implement for_each_css()

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There are enough places where css's of a cgroup are iterated, which
currently uses for_each_root_subsys() + explicit cgroup_css().  This
patch implements for_each_css() and replaces the above combination
with it.

This patch doesn't introduce any behavior changes.

v2: Updated to apply cleanly on top of v2 of "cgroup: fix css leaks on
    online_css() failure"

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-12-06 15:11:56 -05:00
parent c81c925ad9
commit 1c6727af4b
1 changed files with 31 additions and 26 deletions
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57
kernel/cgroup.c
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@ -242,6 +242,21 @@ static int notify_on_release(const struct cgroup *cgrp)
return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
}
/**
* for_each_css - iterate all css's of a cgroup
* @css: the iteration cursor
* @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
* @cgrp: the target cgroup to iterate css's of
*
* Should be called under cgroup_mutex.
*/
#define for_each_css(css, ssid, cgrp) \
for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
if (!((css) = rcu_dereference_check( \
(cgrp)->subsys[(ssid)], \
lockdep_is_held(&cgroup_mutex)))) { } \
else
/**
* for_each_subsys - iterate all loaded cgroup subsystems
* @ss: the iteration cursor
@ -1942,8 +1957,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
bool threadgroup)
{
int retval, i, group_size;
struct cgroup_subsys *ss, *failed_ss = NULL;
struct cgroupfs_root *root = cgrp->root;
struct cgroup_subsys_state *css, *failed_css = NULL;
/* threadgroup list cursor and array */
struct task_struct *leader = tsk;
struct task_and_cgroup *tc;
@ -2016,13 +2031,11 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
/*
* step 1: check that we can legitimately attach to the cgroup.
*/
for_each_root_subsys(root, ss) {
struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
if (ss->can_attach) {
retval = ss->can_attach(css, &tset);
for_each_css(css, i, cgrp) {
if (css->ss->can_attach) {
retval = css->ss->can_attach(css, &tset);
if (retval) {
failed_ss = ss;
failed_css = css;
goto out_cancel_attach;
}
}
@ -2058,12 +2071,9 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
/*
* step 4: do subsystem attach callbacks.
*/
for_each_root_subsys(root, ss) {
struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
if (ss->attach)
ss->attach(css, &tset);
}
for_each_css(css, i, cgrp)
if (css->ss->attach)
css->ss->attach(css, &tset);
/*
* step 5: success! and cleanup
@ -2080,13 +2090,11 @@ out_put_css_set_refs:
}
out_cancel_attach:
if (retval) {
for_each_root_subsys(root, ss) {
struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
if (ss == failed_ss)
for_each_css(css, i, cgrp) {
if (css == failed_css)
break;
if (ss->cancel_attach)
ss->cancel_attach(css, &tset);
if (css->ss->cancel_attach)
css->ss->cancel_attach(css, &tset);
}
}
out_free_group_list:
@ -4375,9 +4383,10 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
struct dentry *d = cgrp->dentry;
struct cgroup_subsys *ss;
struct cgroup_subsys_state *css;
struct cgroup *child;
bool empty;
int ssid;
lockdep_assert_held(&d->d_inode->i_mutex);
lockdep_assert_held(&cgroup_mutex);
@ -4413,12 +4422,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
* will be invoked to perform the rest of destruction once the
* percpu refs of all css's are confirmed to be killed.
*/
for_each_root_subsys(cgrp->root, ss) {
struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
if (css)
kill_css(css);
}
for_each_css(css, ssid, cgrp)
kill_css(css);
/*
* Mark @cgrp dead. This prevents further task migration and child