From 913ffdb54366f94eec65c656cae8c6e00e1ab1b0 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 11 Jul 2013 16:34:48 -0700 Subject: cgroup: replace task_cgroup_path_from_hierarchy() with task_cgroup_path() task_cgroup_path_from_hierarchy() was added for the planned new users and none of the currently planned users wants to know about multiple hierarchies. This patch drops the multiple hierarchy part and makes it always return the path in the first non-dummy hierarchy. As unified hierarchy will always have id 1, this is guaranteed to return the path for the unified hierarchy if mounted; otherwise, it will return the path from the hierarchy which happens to occupy the lowest hierarchy id, which will usually be the first hierarchy mounted after boot. Signed-off-by: Tejun Heo Acked-by: Li Zefan Cc: Lennart Poettering Cc: Kay Sievers Cc: Jan Kaluža --- kernel/cgroup.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) (limited to 'kernel/cgroup.c') diff --git a/kernel/cgroup.c b/kernel/cgroup.c index e5583d10a325..afb8d53ca6c7 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1846,36 +1846,43 @@ out: EXPORT_SYMBOL_GPL(cgroup_path); /** - * task_cgroup_path_from_hierarchy - cgroup path of a task on a hierarchy + * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy * @task: target task - * @hierarchy_id: the hierarchy to look up @task's cgroup from * @buf: the buffer to write the path into * @buflen: the length of the buffer * - * Determine @task's cgroup on the hierarchy specified by @hierarchy_id and - * copy its path into @buf. This function grabs cgroup_mutex and shouldn't - * be used inside locks used by cgroup controller callbacks. + * Determine @task's cgroup on the first (the one with the lowest non-zero + * hierarchy_id) cgroup hierarchy and copy its path into @buf. This + * function grabs cgroup_mutex and shouldn't be used inside locks used by + * cgroup controller callbacks. + * + * Returns 0 on success, fails with -%ENAMETOOLONG if @buflen is too short. */ -int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id, - char *buf, size_t buflen) +int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen) { struct cgroupfs_root *root; - struct cgroup *cgrp = NULL; - int ret = -ENOENT; + struct cgroup *cgrp; + int hierarchy_id = 1, ret = 0; + + if (buflen < 2) + return -ENAMETOOLONG; mutex_lock(&cgroup_mutex); - root = idr_find(&cgroup_hierarchy_idr, hierarchy_id); + root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id); + if (root) { cgrp = task_cgroup_from_root(task, root); ret = cgroup_path(cgrp, buf, buflen); + } else { + /* if no hierarchy exists, everyone is in "/" */ + memcpy(buf, "/", 2); } mutex_unlock(&cgroup_mutex); - return ret; } -EXPORT_SYMBOL_GPL(task_cgroup_path_from_hierarchy); +EXPORT_SYMBOL_GPL(task_cgroup_path); /* * Control Group taskset -- cgit v1.2.3