blkcg: add blkcg_root_css
Add global constant blkcg_root_css which points to &blkcg_root.css.
This will be used by cgroup writeback support. If blkcg is disabled,
it's defined as ERR_PTR(-EINVAL).
v2: The declarations moved to include/linux/blk-cgroup.h as suggested
by Vivek.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 51f95b3..65f0c17 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -134,6 +134,7 @@
};
extern struct blkcg blkcg_root;
+extern struct cgroup_subsys_state * const blkcg_root_css;
struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q);
struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
@@ -570,6 +571,8 @@
struct blkcg_policy {
};
+#define blkcg_root_css ((struct cgroup_subsys_state *)ERR_PTR(-EINVAL))
+
#ifdef CONFIG_BLOCK
static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }