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Commit 1c6727af authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: implement for_each_css() 



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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent c81c925a

kernel/cgroup.c

+31 −26
Original line number Diff line number Diff line
@@ -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 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, 
	}

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)

	for_each_css(css, ssid, cgrp)

		kill_css(css);

	}



	/*

	 * Mark @cgrp dead.  This prevents further task migration and child