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Commit afbcb364 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Tejun Heo
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cgroup: pids: kill pids_fork(), simplify pids_can_fork() and pids_cancel_fork() 



Now that we know that the forking task can't migrate amd the child is always
moved to the same cgroup by cgroup_post_fork()->css_set_move_task() we can
change pids_can_fork() and pids_cancel_fork() to just use task_css(current).
And since we no longer need to pin this css, we can remove pid_fork().

Note: the patch uses task_css_check(true), perhaps it makes sense to add a
helper or change task_css_set_check() to take cgroup_threadgroup_rwsem into
account.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarZefan Li <lizefan@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent c9e75f04

kernel/cgroup_pids.c

+10 −31
Original line number Original line Diff line number Diff line
@@ -205,48 +205,28 @@ static void pids_cancel_attach(struct cgroup_subsys_state *css, 
	}

	}

}

}





/*

 * task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies

 * on threadgroup_change_begin() held by the copy_process().

 */

static int pids_can_fork(struct task_struct *task, void **priv_p)

static int pids_can_fork(struct task_struct *task, void **priv_p)

{

{

	struct cgroup_subsys_state *css;

	struct cgroup_subsys_state *css;

	struct pids_cgroup *pids;

	struct pids_cgroup *pids;

	int err;





	/*

	css = task_css_check(current, pids_cgrp_id, true);

	 * Use the "current" task_css for the pids subsystem as the tentative

	 * css. It is possible we will charge the wrong hierarchy, in which

	 * case we will forcefully revert/reapply the charge on the right

	 * hierarchy after it is committed to the task proper.

	 */

	css = task_get_css(current, pids_cgrp_id);

	pids = css_pids(css);

	pids = css_pids(css);



	return pids_try_charge(pids, 1);

	err = pids_try_charge(pids, 1);

	if (err)

		goto err_css_put;



	*priv_p = css;

	return 0;



err_css_put:

	css_put(css);

	return err;

}

}





static void pids_cancel_fork(struct task_struct *task, void *priv)

static void pids_cancel_fork(struct task_struct *task, void *priv)

{

{

	struct cgroup_subsys_state *css = priv;

	struct cgroup_subsys_state *css;

	struct pids_cgroup *pids = css_pids(css);

	struct pids_cgroup *pids;





	css = task_css_check(current, pids_cgrp_id, true);

	pids = css_pids(css);

	pids_uncharge(pids, 1);

	pids_uncharge(pids, 1);

	css_put(css);

}



static void pids_fork(struct task_struct *task, void *priv)

{

	struct cgroup_subsys_state *css = priv;



	WARN_ON(task_css_check(task, pids_cgrp_id, true) != css);

	css_put(css);

}

}





static void pids_free(struct task_struct *task)

static void pids_free(struct task_struct *task)
@@ -329,7 +309,6 @@ struct cgroup_subsys pids_cgrp_subsys = { 
	.cancel_attach 	= pids_cancel_attach,

	.cancel_attach 	= pids_cancel_attach,

	.can_fork	= pids_can_fork,

	.can_fork	= pids_can_fork,

	.cancel_fork	= pids_cancel_fork,

	.cancel_fork	= pids_cancel_fork,

	.fork		= pids_fork,

	.free		= pids_free,

	.free		= pids_free,

	.legacy_cftypes	= pids_files,

	.legacy_cftypes	= pids_files,

	.dfl_cftypes	= pids_files,

	.dfl_cftypes	= pids_files,