nvme-pci: trace SQ status on completions

Export the disk name, queue id, sq_head, sq_tail to a trace event in
completion handling.

Usage example:

cd /sys/kernel/debug/tracing/events/nvme/nvme_sq

echo 'disk=="nvme1n1"' > filter

echo 1 > enable

cat /sys/kernel/debug/tracing/trace_pipe
Signed-off-by: yupeng <yupeng0921@gmail.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Keith Busch <keith.busch@intel.com>
[hch: slight formatting tweaks, use standard nvme tracepoint
 conventions]
Signed-off-by: Christoph Hellwig <hch@lst.de>

wip

drivers/nvme/host/pci.c

@@ -32,6 +32,7 @@
 #include <linux/sed-opal.h>
 #include <linux/pci-p2pdma.h>
 
+#include "trace.h"
 #include "nvme.h"
 
 #define SQ_SIZE(depth)		(depth * sizeof(struct nvme_command))
@@ -1003,6 +1004,7 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
 	}
 
 	req = blk_mq_tag_to_rq(*nvmeq->tags, cqe->command_id);
+	trace_nvme_sq(req, cqe->sq_head, nvmeq->sq_tail);
 	nvme_end_request(req, cqe->status, cqe->result);
 }
 

drivers/nvme/host/trace.c

@@ -139,3 +139,6 @@ const char *nvme_trace_disk_name(struct trace_seq *p, char *name)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(nvme_trace_disk_name);
+
+EXPORT_TRACEPOINT_SYMBOL_GPL(nvme_sq);

drivers/nvme/host/trace.h

@@ -184,6 +184,29 @@ TRACE_EVENT(nvme_async_event,
 
 #undef aer_name
 
+TRACE_EVENT(nvme_sq,
+	TP_PROTO(struct request *req, __le16 sq_head, int sq_tail),
+	TP_ARGS(req, sq_head, sq_tail),
+	TP_STRUCT__entry(
+		__field(int, ctrl_id)
+		__array(char, disk, DISK_NAME_LEN)
+		__field(int, qid)
+		__field(u16, sq_head)
+		__field(u16, sq_tail)
+	),
+	TP_fast_assign(
+		__entry->ctrl_id = nvme_req(req)->ctrl->instance;
+		__assign_disk_name(__entry->disk, req->rq_disk);
+		__entry->qid = nvme_req_qid(req);
+		__entry->sq_head = le16_to_cpu(sq_head);
+		__entry->sq_tail = sq_tail;
+	),
+	TP_printk("nvme%d: %sqid=%d, head=%u, tail=%u",
+		__entry->ctrl_id, __print_disk_name(__entry->disk),
+		__entry->qid, __entry->sq_head, __entry->sq_tail
+	)
+);
+
 #endif /* _TRACE_NVME_H */
 
 #undef TRACE_INCLUDE_PATH