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

[Damien Le Moal <Damien.LeMoal@wdc.com>]

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