[PATCH] block: introduce for_each_rq_qos macro

[Chunguang Xu <brookxu.cn@gmail.com>]

From: Chunguang Xu <brookxu@tencent.com>

Compared to direct pointer traversal, introducing a macro
will make the code more concise. But the introduction of
macros will make rq_qos_xxx() produce a redundant judgment,
usually this may not be a big problem.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
---
 block/blk-rq-qos.c | 45 ++++++++++++++++++---------------------------
 block/blk-rq-qos.h | 11 +++++++++--
 2 files changed, 27 insertions(+), 29 deletions(-)

diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
index 6564606..2c21a49 100644
--- a/block/blk-rq-qos.c
+++ b/block/blk-rq-qos.c
@@ -31,83 +31,74 @@ bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit)
 
 void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->cleanup)
 			rqos->ops->cleanup(rqos, bio);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 void __rq_qos_done(struct rq_qos *rqos, struct request *rq)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->done)
 			rqos->ops->done(rqos, rq);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 void __rq_qos_issue(struct rq_qos *rqos, struct request *rq)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->issue)
 			rqos->ops->issue(rqos, rq);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->requeue)
 			rqos->ops->requeue(rqos, rq);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->throttle)
 			rqos->ops->throttle(rqos, bio);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->track)
 			rqos->ops->track(rqos, rq, bio);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->merge)
 			rqos->ops->merge(rqos, rq, bio);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->done_bio)
 			rqos->ops->done_bio(rqos, bio);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 void __rq_qos_queue_depth_changed(struct rq_qos *rqos)
 {
-	do {
+	for_each_rq_qos(rqos) {
 		if (rqos->ops->queue_depth_changed)
 			rqos->ops->queue_depth_changed(rqos);
-		rqos = rqos->next;
-	} while (rqos);
+	}
 }
 
 /*
diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h
index 2bc43e9..bfa72a5 100644
--- a/block/blk-rq-qos.h
+++ b/block/blk-rq-qos.h
@@ -57,11 +57,18 @@ struct rq_depth {
 	unsigned int default_depth;
 };
 
+/*
+ * for_each_rq_qos() allows you to iterate on each rqos
+ */
+#define for_each_rq_qos(rqos) \
+	for (; rqos; rqos = rqos->next)
+
 static inline struct rq_qos *rq_qos_id(struct request_queue *q,
 				       enum rq_qos_id id)
 {
-	struct rq_qos *rqos;
-	for (rqos = q->rq_qos; rqos; rqos = rqos->next) {
+	struct rq_qos *rqos = q->rq_qos;
+
+	for_each_rq_qos(rqos) {
 		if (rqos->id == id)
 			break;
 	}
-- 
1.8.3.1