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@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Li Zefan <lizefan@xxxxxxxxxx> Cc: cgroups@xxxxxxxxxxxxxxx Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx> --- /* v1 */ patch not present /* v2 */ patch not present /* v3 */ Link: https://lore.kernel.org/r/20200117002143.15559-3-christian.brauner@xxxxxxxxxx patch introduced - Tejun Heo <tj@xxxxxxxxxx>: - split cgroup_get_from_file() changes into separate commmit /* v4 */ Link: https://lore.kernel.org/r/20200117181219.14542-3-christian.brauner@xxxxxxxxxx unchanged /* v5 */ unchanged --- kernel/cgroup/cgroup.c | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 7b98cc389dae..9b3241d67592 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5875,6 +5875,24 @@ 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. @@ -6163,7 +6181,6 @@ 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; @@ -6171,17 +6188,8 @@ 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); -- 2.25.0
