cgroup writeback support would need to tell whether a given blkcg
cgroup_subsys_state is the root one or not. Add global constant
blkcg_root_css which points to &blkcg_root.css. 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@xxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
---
block/blk-cgroup.c | 2 ++
include/linux/blk-cgroup.h | 3 +++
2 files changed, 5 insertions(+)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index c3226ce..9e0fe38 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -30,6 +30,8 @@ struct blkcg blkcg_root = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT,
.cfq_leaf_weight = 2 * CFQ_WEIGHT_DEFAULT, };
EXPORT_SYMBOL_GPL(blkcg_root);
+struct cgroup_subsys_state * const blkcg_root_css = &blkcg_root.css;
+
static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
static bool blkcg_policy_enabled(struct request_queue *q,
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 @@ struct blkcg_policy {
};
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_gq {
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; }
--
2.1.0
--
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