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cgroup: add cgroup_get_from_file() helper

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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: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Christian Brauner 2020-02-05 14:26:19 +01:00 committed by Tejun Heo
parent 6df970e4f5
commit 17703097f3
1 changed files with 19 additions and 11 deletions
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30
kernel/cgroup/cgroup.c
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@ -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);