[PATCH 5/6] blk-mq: add helper of blk_mq_get_hctx to retrieve hctx via its index

[Ming Lei <ming.lei@redhat.com>]

Prepare for managing hctx mapping via xarray by adding one helper of
blk_mq_get_hctx().

No functional change.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq-sysfs.c   | 2 +-
 block/blk-mq.c         | 4 ++--
 block/blk-mq.h         | 2 +-
 include/linux/blk-mq.h | 8 +++++++-
 4 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 674786574075..22950e764536 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -279,7 +279,7 @@ int __blk_mq_register_dev(struct device *dev, struct request_queue *q)
 
 unreg:
 	while (--i >= 0)
-		blk_mq_unregister_hctx(q->queue_hw_ctx[i]);
+		blk_mq_unregister_hctx(blk_mq_get_hctx(q, i));
 
 	kobject_uevent(q->mq_kobj, KOBJ_REMOVE);
 	kobject_del(q->mq_kobj);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5ce6a8289cff..d01c1693a3d4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -71,7 +71,7 @@ static int blk_mq_poll_stats_bkt(const struct request *rq)
 static inline struct blk_mq_hw_ctx *blk_qc_to_hctx(struct request_queue *q,
 		blk_qc_t qc)
 {
-	return q->queue_hw_ctx[(qc & ~BLK_QC_T_INTERNAL) >> BLK_QC_T_SHIFT];
+	return blk_mq_get_hctx(q, (qc & ~BLK_QC_T_INTERNAL) >> BLK_QC_T_SHIFT);
 }
 
 static inline struct request *blk_qc_to_rq(struct blk_mq_hw_ctx *hctx,
@@ -573,7 +573,7 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
 	 * If not tell the caller that it should skip this queue.
 	 */
 	ret = -EXDEV;
-	data.hctx = q->queue_hw_ctx[hctx_idx];
+	data.hctx = blk_mq_get_hctx(q, hctx_idx);
 	if (!blk_mq_hw_queue_mapped(data.hctx))
 		goto out_queue_exit;
 	cpu = cpumask_first_and(data.hctx->cpumask, cpu_online_mask);
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 948791ea2a3e..804668457f88 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -83,7 +83,7 @@ static inline struct blk_mq_hw_ctx *blk_mq_map_queue_type(struct request_queue *
 							  enum hctx_type type,
 							  unsigned int cpu)
 {
-	return q->queue_hw_ctx[q->tag_set->map[type].mq_map[cpu]];
+	return blk_mq_get_hctx(q, q->tag_set->map[type].mq_map[cpu]);
 }
 
 static inline enum hctx_type blk_mq_get_hctx_type(unsigned int flags)
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 3a41d50b85d3..3d949b1968f3 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -916,9 +916,15 @@ static inline void *blk_mq_rq_to_pdu(struct request *rq)
 	return rq + 1;
 }
 
+static inline struct blk_mq_hw_ctx *blk_mq_get_hctx(struct request_queue *q,
+		unsigned int hctx_idx)
+{
+	return q->queue_hw_ctx[hctx_idx];
+}
+
 #define queue_for_each_hw_ctx(q, hctx, i)				\
 	for ((i) = 0; (i) < (q)->nr_hw_queues &&			\
-	     ({ hctx = (q)->queue_hw_ctx[i]; 1; }); (i)++)
+	     ({ hctx = blk_mq_get_hctx((q), (i)); 1; }); (i)++)
 
 #define hctx_for_each_ctx(hctx, ctx, i)					\
 	for ((i) = 0; (i) < (hctx)->nr_ctx &&				\
-- 
2.31.1