1 files changed, 4 insertions, 48 deletions

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index c41cfcc2b4d8..2951ea3541b1 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -249,47 +249,6 @@ static inline struct cgroup_subsys_state *blkcg_css(void)
 	return task_css(current, io_cgrp_id);
 }
 
-/**
- * blkcg_get_css - find and get a reference to the css
- *
- * Find the css associated with either the kthread or the current task.
- * This takes a reference on the blkcg which will need to be managed by the
- * caller.
- */
-static inline struct cgroup_subsys_state *blkcg_get_css(void)
-{
-	struct cgroup_subsys_state *css;
-
-	rcu_read_lock();
-
-	css = kthread_blkcg();
-	if (css) {
-		css_get(css);
-	} else {
-		/*
-		 * This is a bit complicated.  It is possible task_css is seeing
-		 * an old css pointer here.  This is caused by the current
-		 * thread migrating away from this cgroup and this cgroup dying.
-		 * css_tryget() will fail when trying to take a ref on a cgroup
-		 * that's ref count has hit 0.
-		 *
-		 * Therefore, if it does fail, this means current must have
-		 * been swapped away already and this is waiting for it to
-		 * propagate on the polling cpu.  Hence the use of cpu_relax().
-		 */
-		while (true) {
-			css = task_css(current, io_cgrp_id);
-			if (likely(css_tryget(css)))
-				break;
-			cpu_relax();
-		}
-	}
-
-	rcu_read_unlock();
-
-	return css;
-}
-
 static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
 {
 	return css ? container_of(css, struct blkcg, css) : NULL;
@@ -628,10 +587,8 @@ static inline struct request_list *blk_get_rl(struct request_queue *q,
 	rcu_read_lock();
 
 	blkcg = bio_blkcg(bio);
-	if (blkcg)
-		css_get(&blkcg->css);
-	else
-		blkcg = css_to_blkcg(blkcg_get_css());
+	if (!blkcg)
+		blkcg = css_to_blkcg(blkcg_css());
 
 	/* bypass blkg lookup and use @q->root_rl directly for root */
 	if (blkcg == &blkcg_root)
@@ -646,7 +603,8 @@ static inline struct request_list *blk_get_rl(struct request_queue *q,
 	if (unlikely(!blkg))
 		goto root_rl;
 
-	blkg_get(blkg);
+	if (!blkg_try_get(blkg))
+		goto root_rl;
 	rcu_read_unlock();
 	return &blkg->rl;
 root_rl:
@@ -663,8 +621,6 @@ root_rl:
  */
 static inline void blk_put_rl(struct request_list *rl)
 {
-	/* an additional ref is always taken for rl */
-	css_put(&rl->blkg->blkcg->css);
 	if (rl->blkg->blkcg != &blkcg_root)
 		blkg_put(rl->blkg);
 }