blk-mq-debugfs: support rq_qos

blk-mq-debugfs has been proved as very helpful for debug some
tough issues, such as IO hang.

We have seen blk-wbt related IO hang several times, even inside
Red Hat BZ, there is such report not sovled yet, so this patch
adds support debugfs on rq_qos.

Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 24 insertions, 0 deletions

diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h
index 8678875de420..3c85f26d3846 100644
--- a/block/blk-rq-qos.h
+++ b/block/blk-rq-qos.h
@@ -7,6 +7,10 @@
 #include <linux/atomic.h>
 #include <linux/wait.h>
 
+#include "blk-mq-debugfs.h"
+
+struct blk_mq_debugfs_attr;
+
 enum rq_qos_id {
 	RQ_QOS_WBT,
 	RQ_QOS_CGROUP,
@@ -22,6 +26,9 @@ struct rq_qos {
 	struct request_queue *q;
 	enum rq_qos_id id;
 	struct rq_qos *next;
+#ifdef CONFIG_BLK_DEBUG_FS
+	struct dentry *debugfs_dir;
+#endif
 };
 
 struct rq_qos_ops {
@@ -33,6 +40,7 @@ struct rq_qos_ops {
 	void (*done_bio)(struct rq_qos *, struct bio *);
 	void (*cleanup)(struct rq_qos *, struct bio *);
 	void (*exit)(struct rq_qos *);
+	const struct blk_mq_debugfs_attr *debugfs_attrs;
 };
 
 struct rq_depth {
@@ -66,6 +74,17 @@ static inline struct rq_qos *blkcg_rq_qos(struct request_queue *q)
 	return rq_qos_id(q, RQ_QOS_CGROUP);
 }
 
+static inline const char *rq_qos_id_to_name(enum rq_qos_id id)
+{
+	switch (id) {
+	case RQ_QOS_WBT:
+		return "wbt";
+	case RQ_QOS_CGROUP:
+		return "cgroup";
+	}
+	return "unknown";
+}
+
 static inline void rq_wait_init(struct rq_wait *rq_wait)
 {
 	atomic_set(&rq_wait->inflight, 0);
@@ -76,6 +95,9 @@ static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos)
 {
 	rqos->next = q->rq_qos;
 	q->rq_qos = rqos;
+
+	if (rqos->ops->debugfs_attrs)
+		blk_mq_debugfs_register_rqos(rqos);
 }
 
 static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos)
@@ -91,6 +113,8 @@ static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos)
 		}
 		prev = cur;
 	}
+
+	blk_mq_debugfs_unregister_rqos(rqos);
 }
 
 typedef bool (acquire_inflight_cb_t)(struct rq_wait *rqw, void *private_data);