null_blk: add tracepoint helpers for zoned mode

This patch adds two new tracpoints for null_blk_zoned.c that allows us
to trace report-zones, zone-mgmt-op and zone-write operations which has
direct effect on the zone condition state machine.

Also, we update drivers/block/Makefile so that new null_blk related
tracefiles can be compiled.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/Makefile

@@ -6,6 +6,9 @@
 # Rewritten to use lists instead of if-statements.
 # 
 
+# needed for trace events
+ccflags-y				+= -I$(src)
+
 obj-$(CONFIG_MAC_FLOPPY)	+= swim3.o
 obj-$(CONFIG_BLK_DEV_SWIM)	+= swim_mod.o
 obj-$(CONFIG_BLK_DEV_FD)	+= floppy.o
@@ -39,6 +42,9 @@ obj-$(CONFIG_ZRAM) += zram/
 
 obj-$(CONFIG_BLK_DEV_NULL_BLK)	+= null_blk.o
 null_blk-objs	:= null_blk_main.o
+ifeq ($(CONFIG_BLK_DEV_ZONED), y)
+null_blk-$(CONFIG_TRACING) += null_blk_trace.o
+endif
 null_blk-$(CONFIG_BLK_DEV_ZONED) += null_blk_zoned.o
 
 skd-y		:= skd_main.o

drivers/block/null_blk_trace.c

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * null_blk trace related helpers.
+ *
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ */
+#include "null_blk_trace.h"
+
+/*
+ * Helper to use for all null_blk traces to extract disk name.
+ */
+const char *nullb_trace_disk_name(struct trace_seq *p, char *name)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+
+	if (name && *name)
+		trace_seq_printf(p, "disk=%s, ", name);
+	trace_seq_putc(p, 0);
+
+	return ret;
+}

drivers/block/null_blk_trace.h

@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * null_blk device driver tracepoints.
+ *
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM nullb
+
+#if !defined(_TRACE_NULLB_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_NULLB_H
+
+#include <linux/tracepoint.h>
+#include <linux/trace_seq.h>
+
+#include "null_blk.h"
+
+const char *nullb_trace_disk_name(struct trace_seq *p, char *name);
+
+#define __print_disk_name(name) nullb_trace_disk_name(p, name)
+
+#ifndef TRACE_HEADER_MULTI_READ
+static inline void __assign_disk_name(char *name, struct gendisk *disk)
+{
+	if (disk)
+		memcpy(name, disk->disk_name, DISK_NAME_LEN);
+	else
+		memset(name, 0, DISK_NAME_LEN);
+}
+#endif
+
+TRACE_EVENT(nullb_zone_op,
+	    TP_PROTO(struct nullb_cmd *cmd, unsigned int zone_no,
+		     unsigned int zone_cond),
+	    TP_ARGS(cmd, zone_no, zone_cond),
+	    TP_STRUCT__entry(
+		__array(char, disk, DISK_NAME_LEN)
+		__field(enum req_opf, op)
+		__field(unsigned int, zone_no)
+		__field(unsigned int, zone_cond)
+	    ),
+	    TP_fast_assign(
+		__entry->op = req_op(cmd->rq);
+		__entry->zone_no = zone_no;
+		__entry->zone_cond = zone_cond;
+		__assign_disk_name(__entry->disk, cmd->rq->rq_disk);
+	    ),
+	    TP_printk("%s req=%-15s zone_no=%u zone_cond=%-10s",
+		      __print_disk_name(__entry->disk),
+		      blk_op_str(__entry->op),
+		      __entry->zone_no,
+		      blk_zone_cond_str(__entry->zone_cond))
+);
+
+TRACE_EVENT(nullb_report_zones,
+	    TP_PROTO(struct nullb *nullb, unsigned int nr_zones),
+	    TP_ARGS(nullb, nr_zones),
+	    TP_STRUCT__entry(
+		__array(char, disk, DISK_NAME_LEN)
+		__field(unsigned int, nr_zones)
+	    ),
+	    TP_fast_assign(
+		__entry->nr_zones = nr_zones;
+		__assign_disk_name(__entry->disk, nullb->disk);
+	    ),
+	    TP_printk("%s nr_zones=%u",
+		      __print_disk_name(__entry->disk), __entry->nr_zones)
+);
+
+#endif /* _TRACE_NULLB_H */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE null_blk_trace
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>