blkcg: move root blkg lookup optimization from throtl_lookup_tg() to __blkg_lookup()
Currently, both throttle and cfq policies implement their own root
blkg (blkcg_gq) lookup fast path. This patch moves root blkg
optimization from throtl_lookup_tg() to __blkg_lookup(). cfq-iosched
currently doesn't use blkg_lookup() but will be converted and drop the
optimization too.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index c2c7547..1f63fc8 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -452,13 +452,6 @@
static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td,
struct blkcg *blkcg)
{
- /*
- * This is the common case when there are no blkcgs. Avoid lookup
- * in this case
- */
- if (blkcg == &blkcg_root)
- return td_root_tg(td);
-
return blkg_to_tg(blkg_lookup(blkcg, td->queue));
}
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index d5b54aa..0609bce 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -249,6 +249,9 @@
{
struct blkcg_gq *blkg;
+ if (blkcg == &blkcg_root)
+ return q->root_blkg;
+
blkg = rcu_dereference(blkcg->blkg_hint);
if (blkg && blkg->q == q)
return blkg;
