[PATCH RFC 2/7] block: add helper function fetching gendisk from queue

[Jeffle Xu <jefflexu@linux.alibaba.com>]

Sometimes we need to get the corresponding gendisk from request_queue.

One such use case is that, the block device driver had ever stored the
same private data both in queue->queuedata and gendisk->private_data,
while nowadays gendisk->private_data is more preferable in such case,
e.g. commit c4a59c4e5db3 ("dm: stop using ->queuedata"). So if only
request_queue given, we need to get the corresponding gendisk from
queue, to get the private data stored in gendisk.

Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
 include/linux/blkdev.h       | 2 ++
 include/trace/events/kyber.h | 6 +++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 070de09425ad..2303d06a5a82 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -691,6 +691,8 @@ static inline bool blk_account_rq(struct request *rq)
 	dma_map_page_attrs(dev, (bv)->bv_page, (bv)->bv_offset, (bv)->bv_len, \
 	(dir), (attrs))
 
+#define queue_to_disk(q)	(dev_to_disk(kobj_to_dev((q)->kobj.parent)))
+
 static inline bool queue_is_mq(struct request_queue *q)
 {
 	return q->mq_ops;
diff --git a/include/trace/events/kyber.h b/include/trace/events/kyber.h
index c0e7d24ca256..f9802562edf6 100644
--- a/include/trace/events/kyber.h
+++ b/include/trace/events/kyber.h
@@ -30,7 +30,7 @@ TRACE_EVENT(kyber_latency,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= disk_devt(dev_to_disk(kobj_to_dev(q->kobj.parent)));
+		__entry->dev		= disk_devt(queue_to_disk(q));
 		strlcpy(__entry->domain, domain, sizeof(__entry->domain));
 		strlcpy(__entry->type, type, sizeof(__entry->type));
 		__entry->percentile	= percentile;
@@ -59,7 +59,7 @@ TRACE_EVENT(kyber_adjust,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= disk_devt(dev_to_disk(kobj_to_dev(q->kobj.parent)));
+		__entry->dev		= disk_devt(queue_to_disk(q));
 		strlcpy(__entry->domain, domain, sizeof(__entry->domain));
 		__entry->depth		= depth;
 	),
@@ -81,7 +81,7 @@ TRACE_EVENT(kyber_throttled,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= disk_devt(dev_to_disk(kobj_to_dev(q->kobj.parent)));
+		__entry->dev		= disk_devt(queue_to_disk(q));
 		strlcpy(__entry->domain, domain, sizeof(__entry->domain));
 	),
 
-- 
2.27.0