blk-cgroup: cleanup the blkg_lookup family of functions

Add a fully inlined blkg_lookup as the extra two checks aren't going
to generated a lot more code vs the call to the slowpath routine, and
open code the hint update in the two callers that care.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Andreas Herrmann <aherrmann@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220921180501.1539876-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 15 insertions, 23 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b9a1dcee5a24..d1216760d025 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -263,29 +263,13 @@ err_free:
 	return NULL;
 }
 
-struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
-				      struct request_queue *q, bool update_hint)
+static void blkg_update_hint(struct blkcg *blkcg, struct blkcg_gq *blkg)
 {
-	struct blkcg_gq *blkg;
-
-	/*
-	 * Hint didn't match.  Look up from the radix tree.  Note that the
-	 * hint can only be updated under queue_lock as otherwise @blkg
-	 * could have already been removed from blkg_tree.  The caller is
-	 * responsible for grabbing queue_lock if @update_hint.
-	 */
-	blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
-	if (blkg && blkg->q == q) {
-		if (update_hint) {
-			lockdep_assert_held(&q->queue_lock);
-			rcu_assign_pointer(blkcg->blkg_hint, blkg);
-		}
-		return blkg;
-	}
+	lockdep_assert_held(&blkg->q->queue_lock);
 
-	return NULL;
+	if (blkcg != &blkcg_root && blkg != rcu_dereference(blkcg->blkg_hint))
+		rcu_assign_pointer(blkcg->blkg_hint, blkg);
 }
-EXPORT_SYMBOL_GPL(blkg_lookup_slowpath);
 
 /*
  * If @new_blkg is %NULL, this function tries to allocate a new one as
@@ -397,9 +381,11 @@ static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
 		return blkg;
 
 	spin_lock_irqsave(&q->queue_lock, flags);
-	blkg = __blkg_lookup(blkcg, q, true);
-	if (blkg)
+	blkg = blkg_lookup(blkcg, q);
+	if (blkg) {
+		blkg_update_hint(blkcg, blkg);
 		goto found;
+	}
 
 	/*
 	 * Create blkgs walking down from blkcg_root to @blkcg, so that all
@@ -621,12 +607,18 @@ static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg,
 					  const struct blkcg_policy *pol,
 					  struct request_queue *q)
 {
+	struct blkcg_gq *blkg;
+
 	WARN_ON_ONCE(!rcu_read_lock_held());
 	lockdep_assert_held(&q->queue_lock);
 
 	if (!blkcg_policy_enabled(q, pol))
 		return ERR_PTR(-EOPNOTSUPP);
-	return __blkg_lookup(blkcg, q, true /* update_hint */);
+
+	blkg = blkg_lookup(blkcg, q);
+	if (blkg)
+		blkg_update_hint(blkcg, blkg);
+	return blkg;
 }
 
 /**