Commit 17703097 authored by Christian Brauner's avatar Christian Brauner Committed by Tejun Heo
Browse files

cgroup: add cgroup_get_from_file() helper 



Add a helper cgroup_get_from_file(). The helper will be used in
subsequent patches to retrieve a cgroup while holding a reference to the
struct file it was taken from.

Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: cgroups@vger.kernel.org
Acked-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarChristian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 6df970e4

kernel/cgroup/cgroup.c

+19 −11
Original line number Diff line number Diff line
@@ -5880,6 +5880,24 @@ void cgroup_fork(struct task_struct *child) 
	INIT_LIST_HEAD(&child->cg_list);

}



static struct cgroup *cgroup_get_from_file(struct file *f)

{

	struct cgroup_subsys_state *css;

	struct cgroup *cgrp;



	css = css_tryget_online_from_dir(f->f_path.dentry, NULL);

	if (IS_ERR(css))

		return ERR_CAST(css);



	cgrp = css->cgroup;

	if (!cgroup_on_dfl(cgrp)) {

		cgroup_put(cgrp);

		return ERR_PTR(-EBADF);

	}



	return cgrp;

}



/**

 * cgroup_can_fork - called on a new task before the process is exposed

 * @child: the task in question.
@@ -6171,7 +6189,6 @@ EXPORT_SYMBOL_GPL(cgroup_get_from_path); 
 */

struct cgroup *cgroup_get_from_fd(int fd)

{

	struct cgroup_subsys_state *css;

	struct cgroup *cgrp;

	struct file *f;
@@ -6179,17 +6196,8 @@ struct cgroup *cgroup_get_from_fd(int fd) 
	if (!f)

		return ERR_PTR(-EBADF);



	css = css_tryget_online_from_dir(f->f_path.dentry, NULL);

	cgrp = cgroup_get_from_file(f);

	fput(f);

	if (IS_ERR(css))

		return ERR_CAST(css);



	cgrp = css->cgroup;

	if (!cgroup_on_dfl(cgrp)) {

		cgroup_put(cgrp);

		return ERR_PTR(-EBADF);

	}



	return cgrp;

}

EXPORT_SYMBOL_GPL(cgroup_get_from_fd);

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