diff options
| author | Tejun Heo <tj@kernel.org> | 2015-05-22 23:13:22 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2015-06-02 16:33:34 +0200 |
| commit | ec438699a9ae0856c2ce20a50dd39cdc7e92a732 (patch) | |
| tree | f7406e5c235380474bf829639feed12bf0711101 /include | |
| parent | blkcg: add blkcg_root_css (diff) | |
| download | linux-ec438699a9ae0856c2ce20a50dd39cdc7e92a732.tar.xz linux-ec438699a9ae0856c2ce20a50dd39cdc7e92a732.zip | |
cgroup, block: implement task_get_css() and use it in bio_associate_current()
bio_associate_current() currently open codes task_css() and
css_tryget_online() to find and pin $current's blkcg css. Abstract it
into task_get_css() which is implemented from cgroup side. As a task
is always associated with an online css for every subsystem except
while the css_set update is propagating, task_get_css() retries till
css_tryget_online() succeeds.
This is a cleanup and shouldn't lead to noticeable behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/cgroup.h | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index b9cb94c3102a..e7da0aa65b2d 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -774,6 +774,31 @@ static inline struct cgroup_subsys_state *task_css(struct task_struct *task, } /** + * task_get_css - find and get the css for (task, subsys) + * @task: the target task + * @subsys_id: the target subsystem ID + * + * Find the css for the (@task, @subsys_id) combination, increment a + * reference on and return it. This function is guaranteed to return a + * valid css. + */ +static inline struct cgroup_subsys_state * +task_get_css(struct task_struct *task, int subsys_id) +{ + struct cgroup_subsys_state *css; + + rcu_read_lock(); + while (true) { + css = task_css(task, subsys_id); + if (likely(css_tryget_online(css))) + break; + cpu_relax(); + } + rcu_read_unlock(); + return css; +} + +/** * task_css_is_root - test whether a task belongs to the root css * @task: the target task * @subsys_id: the target subsystem ID |