[PATCH 0/3] null_blk: add tracnepoints for zoned mode

[PATCH 0/3] null_blk: add tracnepoints for zoned mode

[Chaitanya Kulkarni]

Hi,

Recently we've added several new operations for zoned block devices
blk-zone.c ZBD). These operations have a direct effect on the
zone-state machine present in the null_blk_zoned.c. 

This will allow us to add new testcases in blktests in order to verify
the correct operations on the driver side.

This is a small patch series which adds tracepoints for the null_blk
block driver when configured in a zoned mode (with command line
parameter zoned=1).

The first patch is a prep patch that adds a helper to stringify zone
conditions which we use in the trace, the second patch adds new
tracepoint definitions and the third patch allows null_blk_zoned to
trace operations.

Please have a look at the end for sample output.

P.S. I've kept the helper function blk_zone_cond_str() into header
file, please let me know if it needs to be in the blk-zoned.c.

Regards,
Chaitanya              

Chaitanya Kulkarni (3):
  block: add zone condition debug helpers
  null_blk: add tracepoint helpers for zoned mode
  null_blk: add trace in null_blk_zoned.c

 block/blk-zoned.c              | 14 ++++++
 drivers/block/Makefile         |  3 ++
 drivers/block/null_blk_trace.c | 20 +++++++++
 drivers/block/null_blk_trace.h | 78 ++++++++++++++++++++++++++++++++++
 drivers/block/null_blk_zoned.c | 12 +++++-
 include/linux/blkdev.h         | 26 ++++++++++++
 include/uapi/linux/blkzoned.h  |  1 +
 7 files changed, 153 insertions(+), 1 deletion(-)
 create mode 100644 drivers/block/null_blk_trace.c
 create mode 100644 drivers/block/null_blk_trace.h

Sample Test Output :-

# modprobe null_blk zoned=1 zone_size=128 gb=1 bs=4096
# cd /sys/kernel/debug/tracing/
# echo 1 > events/nullb/enable; cat trace_pipe 
# for i in open close finish reset; do blkzone $i /dev/nullb0; done 
# dd if=/dev/zero of=/dev/nullb0 bs=4k count=5

nullb_zone_op: disk=nullb0,  req=ZONE_OPEN       zone_no=0 zone_cond=EXP_OPEN  
nullb_zone_op: disk=nullb0,  req=ZONE_OPEN       zone_no=1 zone_cond=EXP_OPEN  
nullb_zone_op: disk=nullb0,  req=ZONE_OPEN       zone_no=2 zone_cond=EXP_OPEN  
nullb_zone_op: disk=nullb0,  req=ZONE_OPEN       zone_no=3 zone_cond=EXP_OPEN  
nullb_zone_op: disk=nullb0,  req=ZONE_OPEN       zone_no=4 zone_cond=EXP_OPEN  
nullb_zone_op: disk=nullb0,  req=ZONE_OPEN       zone_no=5 zone_cond=EXP_OPEN  
nullb_zone_op: disk=nullb0,  req=ZONE_OPEN       zone_no=6 zone_cond=EXP_OPEN  
nullb_zone_op: disk=nullb0,  req=ZONE_OPEN       zone_no=7 zone_cond=EXP_OPEN  
nullb_zone_op: disk=nullb0,  req=ZONE_CLOSE      zone_no=0 zone_cond=EMPTY     
nullb_zone_op: disk=nullb0,  req=ZONE_CLOSE      zone_no=1 zone_cond=EMPTY     
nullb_zone_op: disk=nullb0,  req=ZONE_CLOSE      zone_no=2 zone_cond=EMPTY     
nullb_zone_op: disk=nullb0,  req=ZONE_CLOSE      zone_no=3 zone_cond=EMPTY     
nullb_zone_op: disk=nullb0,  req=ZONE_CLOSE      zone_no=4 zone_cond=EMPTY     
nullb_zone_op: disk=nullb0,  req=ZONE_CLOSE      zone_no=5 zone_cond=EMPTY     
nullb_zone_op: disk=nullb0,  req=ZONE_CLOSE      zone_no=6 zone_cond=EMPTY     
nullb_zone_op: disk=nullb0,  req=ZONE_CLOSE      zone_no=7 zone_cond=EMPTY     
nullb_zone_op: disk=nullb0,  req=ZONE_FINISH     zone_no=0 zone_cond=FULL      
nullb_zone_op: disk=nullb0,  req=ZONE_FINISH     zone_no=1 zone_cond=FULL      
nullb_zone_op: disk=nullb0,  req=ZONE_FINISH     zone_no=2 zone_cond=FULL      
nullb_zone_op: disk=nullb0,  req=ZONE_FINISH     zone_no=3 zone_cond=FULL      
nullb_zone_op: disk=nullb0,  req=ZONE_FINISH     zone_no=4 zone_cond=FULL      
nullb_zone_op: disk=nullb0,  req=ZONE_FINISH     zone_no=5 zone_cond=FULL      
nullb_zone_op: disk=nullb0,  req=ZONE_FINISH     zone_no=6 zone_cond=FULL      
nullb_zone_op: disk=nullb0,  req=ZONE_FINISH     zone_no=7 zone_cond=FULL      
nullb_zone_op: disk=nullb0,  req=ZONE_RESET_ALL  zone_no=0 zone_cond=EMPTY 
nullb_zone_op: disk=nullb0,  req=WRITE           zone_no=0 zone_cond=IMP_OPEN  
nullb_zone_op: disk=nullb0,  req=WRITE           zone_no=0 zone_cond=IMP_OPEN  
nullb_zone_op: disk=nullb0,  req=WRITE           zone_no=0 zone_cond=IMP_OPEN  
nullb_zone_op: disk=nullb0,  req=WRITE           zone_no=0 zone_cond=IMP_OPEN  
nullb_zone_op: disk=nullb0,  req=WRITE           zone_no=0 zone_cond=IMP_OPEN
-- 
2.22.1

[PATCH 1/3] block: add a zone condition debug helper

[Chaitanya Kulkarni]

Add a helper to stringify the zone conditions. We use this helper in the
next patch to track zone conditions in tracepoints.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
---
 block/blk-zoned.c             | 14 ++++++++++++++
 include/linux/blkdev.h        | 26 ++++++++++++++++++++++++++
 include/uapi/linux/blkzoned.h |  1 +
 3 files changed, 41 insertions(+)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 05741c6f618b..2c4df98b513c 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -20,6 +20,20 @@
 
 #include "blk.h"
 
+#define ZONE_COND_NAME(name) [BLK_ZONE_COND_##name] = #name
+const char *const zone_cond_name[BLK_ZONE_COND_LAST] = {
+	ZONE_COND_NAME(NOT_WP),
+	ZONE_COND_NAME(EMPTY),
+	ZONE_COND_NAME(IMP_OPEN),
+	ZONE_COND_NAME(EXP_OPEN),
+	ZONE_COND_NAME(CLOSED),
+	ZONE_COND_NAME(READONLY),
+	ZONE_COND_NAME(FULL),
+	ZONE_COND_NAME(OFFLINE),
+};
+EXPORT_SYMBOL_GPL(zone_cond_name);
+#undef ZONE_COND_NAME
+
 static inline sector_t blk_zone_start(struct request_queue *q,
 				      sector_t sector)
 {
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 053ea4b51988..5204eda6e4c1 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -887,6 +887,32 @@ extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,
 /* Helper to convert REQ_OP_XXX to its string format XXX */
 extern const char *blk_op_str(unsigned int op);
 
+#ifdef CONFIG_BLK_DEV_ZONED
+extern const char *const zone_cond_name[BLK_ZONE_COND_LAST];
+/**
+ * blk_zone_cond_str - Return string XXX in BLK_ZONE_COND_XXX.
+ * @zone_cond: BLK_ZONE_COND_XXX.
+ *
+ * Description: Centralize block layer function to convert BLK_ZONE_COND_XXX
+ * into string format. Useful in the debugging and tracing zone conditions. For
+ * invalid BLK_ZONE_COND_XXX it returns string "UNKNOWN".
+ */
+static inline const char *blk_zone_cond_str(enum blk_zone_cond zone_cond)
+{
+	const char *zone_cond_str = "UNKNOWN";
+
+	if (zone_cond < BLK_ZONE_COND_LAST && zone_cond_name[zone_cond])
+		zone_cond_str = zone_cond_name[zone_cond];
+
+	return zone_cond_str;
+}
+#else
+static inline const char *blk_zone_cond_str(unsigned int zone_cond)
+{
+	return "NOT SUPPORTED";
+}
+#endif /* CONFIG_BLK_DEV_ZONED */
+
 int blk_status_to_errno(blk_status_t status);
 blk_status_t errno_to_blk_status(int errno);
 
diff --git a/include/uapi/linux/blkzoned.h b/include/uapi/linux/blkzoned.h
index 0cdef67135f0..28ad29973a45 100644
--- a/include/uapi/linux/blkzoned.h
+++ b/include/uapi/linux/blkzoned.h
@@ -71,6 +71,7 @@ enum blk_zone_cond {
 	BLK_ZONE_COND_READONLY	= 0xD,
 	BLK_ZONE_COND_FULL	= 0xE,
 	BLK_ZONE_COND_OFFLINE	= 0xF,
+	BLK_ZONE_COND_LAST,
 };
 
 /**
-- 
2.22.1

[PATCH 2/3] null_blk: add tracepoint helpers for zoned mode

[Chaitanya Kulkarni]

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>
---
 drivers/block/Makefile         |  3 ++
 drivers/block/null_blk_trace.c | 20 +++++++++
 drivers/block/null_blk_trace.h | 78 ++++++++++++++++++++++++++++++++++
 3 files changed, 101 insertions(+)
 create mode 100644 drivers/block/null_blk_trace.c
 create mode 100644 drivers/block/null_blk_trace.h

diff --git a/drivers/block/Makefile b/drivers/block/Makefile
index a53cc1e3a2d3..b05aa413f7c0 100644
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -6,6 +6,8 @@
 # Rewritten to use lists instead of if-statements.
 # 
 
+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 +41,7 @@ obj-$(CONFIG_ZRAM) += zram/
 
 obj-$(CONFIG_BLK_DEV_NULL_BLK)	+= null_blk.o
 null_blk-objs	:= null_blk_main.o
+null_blk-$(CONFIG_TRACING)	+= null_blk_trace.o
 null_blk-$(CONFIG_BLK_DEV_ZONED) += null_blk_zoned.o
 
 skd-y		:= skd_main.o
diff --git a/drivers/block/null_blk_trace.c b/drivers/block/null_blk_trace.c
new file mode 100644
index 000000000000..bd066130ff39
--- /dev/null
+++ b/drivers/block/null_blk_trace.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * All trace related helpers for null_blk goes here.
+ */
+#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;
+}
diff --git a/drivers/block/null_blk_trace.h b/drivers/block/null_blk_trace.h
new file mode 100644
index 000000000000..8171bc26f6d1
--- /dev/null
+++ b/drivers/block/null_blk_trace.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * null_blk device driver tracepoints.
+ */
+
+#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>
-- 
2.22.1

[PATCH 3/3] null_blk: add trace in null_blk_zoned.c

[Chaitanya Kulkarni]

With the help of previously added tracepoints we can now trace
report-zones, zone-write and zone-mgmt ops in null_blk_zoned.c.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
---
 drivers/block/null_blk_zoned.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/block/null_blk_zoned.c b/drivers/block/null_blk_zoned.c
index ed34785dd64b..673618d8222a 100644
--- a/drivers/block/null_blk_zoned.c
+++ b/drivers/block/null_blk_zoned.c
@@ -2,6 +2,9 @@
 #include <linux/vmalloc.h>
 #include "null_blk.h"
 
+#define CREATE_TRACE_POINTS
+#include "null_blk_trace.h"
+
 /* zone_size in MBs to sectors. */
 #define ZONE_SIZE_SHIFT		11
 
@@ -80,6 +83,8 @@ int null_report_zones(struct gendisk *disk, sector_t sector,
 		return 0;
 
 	nr_zones = min(nr_zones, dev->nr_zones - first_zone);
+	trace_nullb_report_zones(nullb, nr_zones);
+
 	for (i = 0; i < nr_zones; i++) {
 		/*
 		 * Stacked DM target drivers will remap the zone information by
@@ -148,6 +153,8 @@ static blk_status_t null_zone_write(struct nullb_cmd *cmd, sector_t sector,
 		/* Invalid zone condition */
 		return BLK_STS_IOERR;
 	}
+
+	trace_nullb_zone_op(cmd, zno, zone->cond);
 	return BLK_STS_OK;
 }
 
@@ -155,7 +162,8 @@ static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
 				   sector_t sector)
 {
 	struct nullb_device *dev = cmd->nq->dev;
-	struct blk_zone *zone = &dev->zones[null_zone_no(dev, sector)];
+	unsigned int zone_no = null_zone_no(dev, sector);
+	struct blk_zone *zone = &dev->zones[zone_no];
 	size_t i;
 
 	switch (op) {
@@ -203,6 +211,8 @@ static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
 	default:
 		return BLK_STS_NOTSUPP;
 	}
+
+	trace_nullb_zone_op(cmd, zone_no, zone->cond);
 	return BLK_STS_OK;
 }
 
-- 
2.22.1

Re: [PATCH 1/3] block: add a zone condition debug helper

[Damien Le Moal]

On 2020/02/15 9:58, Chaitanya Kulkarni wrote:
> Add a helper to stringify the zone conditions. We use this helper in the
> next patch to track zone conditions in tracepoints.
> 
> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
> ---
>  block/blk-zoned.c             | 14 ++++++++++++++
>  include/linux/blkdev.h        | 26 ++++++++++++++++++++++++++
>  include/uapi/linux/blkzoned.h |  1 +
>  3 files changed, 41 insertions(+)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 05741c6f618b..2c4df98b513c 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -20,6 +20,20 @@
>  
>  #include "blk.h"
>  
> +#define ZONE_COND_NAME(name) [BLK_ZONE_COND_##name] = #name
> +const char *const zone_cond_name[BLK_ZONE_COND_LAST] = {

Is the BLK_ZONE_COND_LAST really necessary ?

> +	ZONE_COND_NAME(NOT_WP),
> +	ZONE_COND_NAME(EMPTY),
> +	ZONE_COND_NAME(IMP_OPEN),
> +	ZONE_COND_NAME(EXP_OPEN),
> +	ZONE_COND_NAME(CLOSED),
> +	ZONE_COND_NAME(READONLY),
> +	ZONE_COND_NAME(FULL),
> +	ZONE_COND_NAME(OFFLINE),
> +};
> +EXPORT_SYMBOL_GPL(zone_cond_name);

Instead of exporting this, why not keep it static and export the function
blk_zone_cond_str() ? Any particular reason ? Does blk_zone_cond_str() need
to be inline ?

> +#undef ZONE_COND_NAME
> +
>  static inline sector_t blk_zone_start(struct request_queue *q,
>  				      sector_t sector)
>  {
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 053ea4b51988..5204eda6e4c1 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -887,6 +887,32 @@ extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,
>  /* Helper to convert REQ_OP_XXX to its string format XXX */
>  extern const char *blk_op_str(unsigned int op);
>  
> +#ifdef CONFIG_BLK_DEV_ZONED
> +extern const char *const zone_cond_name[BLK_ZONE_COND_LAST];
> +/**
> + * blk_zone_cond_str - Return string XXX in BLK_ZONE_COND_XXX.
> + * @zone_cond: BLK_ZONE_COND_XXX.
> + *
> + * Description: Centralize block layer function to convert BLK_ZONE_COND_XXX
> + * into string format. Useful in the debugging and tracing zone conditions. For
> + * invalid BLK_ZONE_COND_XXX it returns string "UNKNOWN".
> + */
> +static inline const char *blk_zone_cond_str(enum blk_zone_cond zone_cond)
> +{
> +	const char *zone_cond_str = "UNKNOWN";

Shouldn't this be "static const char *..." ?

> +
> +	if (zone_cond < BLK_ZONE_COND_LAST && zone_cond_name[zone_cond])
> +		zone_cond_str = zone_cond_name[zone_cond];
> +
> +	return zone_cond_str;
> +}
> +#else
> +static inline const char *blk_zone_cond_str(unsigned int zone_cond)
> +{
> +	return "NOT SUPPORTED";
> +}
> +#endif /* CONFIG_BLK_DEV_ZONED */
> +
>  int blk_status_to_errno(blk_status_t status);
>  blk_status_t errno_to_blk_status(int errno);
>  
> diff --git a/include/uapi/linux/blkzoned.h b/include/uapi/linux/blkzoned.h
> index 0cdef67135f0..28ad29973a45 100644
> --- a/include/uapi/linux/blkzoned.h
> +++ b/include/uapi/linux/blkzoned.h
> @@ -71,6 +71,7 @@ enum blk_zone_cond {
>  	BLK_ZONE_COND_READONLY	= 0xD,
>  	BLK_ZONE_COND_FULL	= 0xE,
>  	BLK_ZONE_COND_OFFLINE	= 0xF,
> +	BLK_ZONE_COND_LAST,

Is this really necessary ?

>  };
>  
>  /**
> 


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH 2/3] null_blk: add tracepoint helpers for zoned mode

[Damien Le Moal]

On 2020/02/15 9:58, Chaitanya Kulkarni wrote:
> 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>
> ---
>  drivers/block/Makefile         |  3 ++
>  drivers/block/null_blk_trace.c | 20 +++++++++
>  drivers/block/null_blk_trace.h | 78 ++++++++++++++++++++++++++++++++++
>  3 files changed, 101 insertions(+)
>  create mode 100644 drivers/block/null_blk_trace.c
>  create mode 100644 drivers/block/null_blk_trace.h
> 
> diff --git a/drivers/block/Makefile b/drivers/block/Makefile
> index a53cc1e3a2d3..b05aa413f7c0 100644
> --- a/drivers/block/Makefile
> +++ b/drivers/block/Makefile
> @@ -6,6 +6,8 @@
>  # Rewritten to use lists instead of if-statements.
>  # 
>  
> +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 +41,7 @@ obj-$(CONFIG_ZRAM) += zram/
>  
>  obj-$(CONFIG_BLK_DEV_NULL_BLK)	+= null_blk.o
>  null_blk-objs	:= null_blk_main.o
> +null_blk-$(CONFIG_TRACING)	+= null_blk_trace.o

Since the traces are for zoned operations only, why compile this if
CONFIG_BLK_DEV_ZONED is not enabled ?

>  null_blk-$(CONFIG_BLK_DEV_ZONED) += null_blk_zoned.o
>  
>  skd-y		:= skd_main.o
> diff --git a/drivers/block/null_blk_trace.c b/drivers/block/null_blk_trace.c
> new file mode 100644
> index 000000000000..bd066130ff39
> --- /dev/null
> +++ b/drivers/block/null_blk_trace.c
> @@ -0,0 +1,20 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * All trace related helpers for null_blk goes here.
> + */
> +#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;
> +}
> diff --git a/drivers/block/null_blk_trace.h b/drivers/block/null_blk_trace.h
> new file mode 100644
> index 000000000000..8171bc26f6d1
> --- /dev/null
> +++ b/drivers/block/null_blk_trace.h
> @@ -0,0 +1,78 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * null_blk device driver tracepoints.
> + */
> +
> +#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>
> 


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH 3/3] null_blk: add trace in null_blk_zoned.c

[Damien Le Moal]

On 2020/02/15 9:58, Chaitanya Kulkarni wrote:
> With the help of previously added tracepoints we can now trace
> report-zones, zone-write and zone-mgmt ops in null_blk_zoned.c.
> 
> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

Looks good to me.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal
Western Digital Research