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Filename : ioscheduler.stp
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// IO scheduler tapset
// Copyright (C) 2005, 2006 IBM Corp.
// Copyright (C) 2010-2017 Red Hat Inc.
//
// This file is part of systemtap, and is free software.  You can
// redistribute it and/or modify it under the terms of the GNU General
// Public License (GPL); either version 2, or (at your option) any
// later version.
// <tapsetdescription>
// This family of probe points is used to probe IO scheduler activities. 
// </tapsetdescription>
%{
#include <linux/blkdev.h>
#include <linux/elevator.h>
%}

/**
 * probe ioscheduler.elv_next_request - Fires when a request is retrieved from the request queue
 * @name: Name of the probe point
 * @elevator_name: The type of I/O elevator currently enabled
 */
probe ioscheduler.elv_next_request = kernel.function("blk_peek_request") !,
				     kernel.function("elv_next_request")
{
	name = "elv_next_request"
	elevator_name = kernel_string(
		@choose_defined($q->elevator->type->elevator_name,
			@choose_defined($q->elevator->elevator_type->elevator_name,
                                        $q->elevator->elevator_name)), "")
}

/**
 * probe ioscheduler.elv_next_request.return - Fires when a request retrieval issues a return signal
 * @name: Name of the probe point
 * @rq: Address of the request
 * @rq_flags: Request flags
 * @disk_major: Disk major number of the request
 * @disk_minor: Disk minor number of the request
 */
probe ioscheduler.elv_next_request.return =
		kernel.function("blk_peek_request").return !,
		kernel.function("elv_next_request").return
{
	name = "elv_next_request"
	if ($return == 0)  {
		rq = 0
		rq_flags = 0
		disk_major = -1
		disk_minor = -1
	} else {
		rq = $return
		rq_flags = @choose_defined($return->cmd_flags, $return->flags)
		if ($return->rq_disk == 0)  {
			disk_major = -1
			disk_minor = -1
		} else {
			disk_major = $return->rq_disk->major
			disk_minor = $return->rq_disk->first_minor
		}
	}
}

/**
 * probe ioscheduler.elv_completed_request - Fires when a request is completed
 * @name: Name of the probe point
 * @elevator_name: The type of I/O elevator currently enabled
 * @rq: Address of the request
 * @rq_flags: Request flags
 * @disk_major: Disk major number of the request
 * @disk_minor: Disk minor number of the request
 */
probe ioscheduler.elv_completed_request
	= kernel.function("elv_completed_request")
{
	name = "elv_completed_request"
	elevator_name = kernel_string(
		@choose_defined($q->elevator->type->elevator_name,
			@choose_defined($q->elevator->elevator_type->elevator_name,
                                        $q->elevator->elevator_name)), "")
	if($rq == 0)  {
		disk_major = -1
		disk_minor = -1
	} else {
		if($rq->rq_disk == 0)  {
			disk_major = -1
			disk_minor = -1
		} else {
			disk_major = $rq->rq_disk->major
			disk_minor = $rq->rq_disk->first_minor
		}
	}

	rq = $rq
	rq_flags = ($rq == 0) ? 0
		: @choose_defined($rq->cmd_flags, $rq->flags)
}

/**
 * probe ioscheduler.elv_add_request.kp - kprobe based probe to indicate that a request was added to the request queue
 * @name: Name of the probe point
 * @elevator_name: The type of I/O elevator currently enabled
 * @q: pointer to request queue
 * @rq: Address of the request
 * @rq_flags: Request flags
 * @disk_major: Disk major number of the request
 * @disk_minor: Disk minor number of the request
 */
// when a request is added to the request queue
probe ioscheduler.elv_add_request.kp =
		kernel.function("elv_insert") !,
		kernel.function("__elv_add_request")
{
	name = "elv_add_request"
	elevator_name = kernel_string(
		@choose_defined($q->elevator->type->elevator_name,
			@choose_defined($q->elevator->elevator_type->elevator_name,
                                        $q->elevator->elevator_name)), "")
	q = $q
	if($rq == 0)  {
		disk_major = -1
		disk_minor = -1
	} else {
		if($rq->rq_disk == 0)  {
			disk_major = -1
			disk_minor = -1
		} else {
			disk_major = $rq->rq_disk->major
			disk_minor = $rq->rq_disk->first_minor
		}
	}

	rq = $rq
	rq_flags = ($rq == 0) ? 0
		: @choose_defined($rq->cmd_flags, $rq->flags)
}

/**
 * probe ioscheduler.elv_add_request.tp - tracepoint based probe to indicate a request is added to the request queue.
 * @name		: Name of the probe point
 * @elevator_name	: The type of I/O elevator currently enabled.
 * @q			: Pointer to request queue.
 * @rq			: Address of request.
 * @rq_flags		: Request flags.
 * @disk_major		: Disk major no of request.
 * @disk_minor		: Disk minor number of request.
 *
 */
probe ioscheduler.elv_add_request.tp = kernel.trace("block_rq_insert") ?
{
	name = "elv_add_request"
	q =  $q
	elevator_name = ($q->elevator == 0) ? "" : kernel_string(
		@choose_defined($q->elevator->type->elevator_name,
			@choose_defined($q->elevator->elevator_type->elevator_name,
                                        $q->elevator->elevator_name)), "")
	rq = $rq

	if ($rq == 0 || $rq->rq_disk ==0) {
		disk_major = -1
		disk_minor = -1
	}
	else {
		disk_major = $rq->rq_disk->major
		disk_minor = $rq->rq_disk->first_minor
	}

	rq_flags = ($rq == 0) ? 0
		: @choose_defined($rq->cmd_flags, $rq->flags)
}

/**
 * probe ioscheduler.elv_add_request - probe to indicate request is added to the request queue.
 * @elevator_name	: The type of I/O elevator currently enabled.
 * @q			: Pointer to request queue.
 * @rq			: Address of request.
 * @rq_flags		: Request flags.
 * @disk_major		: Disk major no of request.
 * @disk_minor		: Disk minor number of request.
 *
 */
probe ioscheduler.elv_add_request =
	ioscheduler.elv_add_request.tp !, ioscheduler.elv_add_request.kp
{}

/**
 * probe ioscheduler_trace.elv_completed_request - Fires when a request is
 *							completed.
 * @name		: Name of the probe point
 * @elevator_name	: The type of I/O elevator currently enabled.
 * @rq			: Address of request.
 * @rq_flags		: Request flags.
 * @disk_major		: Disk major no of request.
 * @disk_minor		: Disk minor number of request.
 *
 */
probe ioscheduler_trace.elv_completed_request
			= kernel.trace("block_rq_complete") ?
{
	name = "elv_completed_request"
	if (@defined($q)) {
		elevator_name = kernel_string(
			@choose_defined($q->elevator->type->elevator_name,
				@choose_defined($q->elevator->elevator_type->elevator_name,
                                                $q->elevator->elevator_name)), "")
	}
	else {
		elevator_name = kernel_string($rq->q->elevator->type->elevator_name)
	}
	rq = $rq

	if ($rq == 0 || $rq->rq_disk ==0) {
		disk_major = -1
		disk_minor = -1
	}
	else {
		disk_major = $rq->rq_disk->major
		disk_minor = $rq->rq_disk->first_minor
	}

	rq_flags = ($rq == 0) ? 0
		: @choose_defined($rq->cmd_flags, $rq->flags)
}

/**
 * probe ioscheduler_trace.elv_issue_request - Fires when a request is
 *							scheduled.
 * @name		: Name of the probe point
 * @elevator_name	: The type of I/O elevator currently enabled.
 * @rq			: Address of request.
 * @rq_flags		: Request flags.
 * @disk_major		: Disk major no of request.
 * @disk_minor		: Disk minor number of request.
 *
 */
probe ioscheduler_trace.elv_issue_request
			= kernel.trace("block_rq_issue") ?
{
	name = "elv_issue_request"
	elevator_name = kernel_string(
		@choose_defined($q->elevator->type->elevator_name,
			@choose_defined($q->elevator->elevator_type->elevator_name,
                                        $q->elevator->elevator_name)), "")
	rq = $rq

	if ($rq == 0 || $rq->rq_disk ==0) {
		disk_major = -1
		disk_minor = -1
	}
	else {
		disk_major = $rq->rq_disk->major
		disk_minor = $rq->rq_disk->first_minor
	}

	rq_flags = ($rq == 0) ? 0
		: @choose_defined($rq->cmd_flags, $rq->flags)
}

/**
 * probe ioscheduler_trace.elv_requeue_request - Fires when a request is
 *	put back on the queue, when the hadware cannot accept more requests.
 * @name		: Name of the probe point
 * @elevator_name	: The type of I/O elevator currently enabled.
 * @rq			: Address of request.
 * @rq_flags		: Request flags.
 * @disk_major		: Disk major no of request.
 * @disk_minor		: Disk minor number of request.
 *
 */
probe ioscheduler_trace.elv_requeue_request
			= kernel.trace("block_rq_requeue") ?
{
	name = "elv_requeue_request"
	elevator_name = kernel_string(
		@choose_defined($q->elevator->type->elevator_name,
			@choose_defined($q->elevator->elevator_type->elevator_name,
                                        $q->elevator->elevator_name)), "")
	rq = $rq

	if ($rq == 0 || $rq->rq_disk ==0) {
		disk_major = -1
		disk_minor = -1
	}
	else {
		disk_major = $rq->rq_disk->major
		disk_minor = $rq->rq_disk->first_minor
	}

	rq_flags = ($rq == 0) ? 0
		: @choose_defined($rq->cmd_flags, $rq->flags)
}

/**
 * probe ioscheduler_trace.elv_abort_request - Fires when a request is aborted.
 * @name		: Name of the probe point
 * @elevator_name	: The type of I/O elevator currently enabled.
 * @rq			: Address of request.
 * @rq_flags		: Request flags.
 * @disk_major		: Disk major no of request.
 * @disk_minor		: Disk minor number of request.
 *
 */
probe ioscheduler_trace.elv_abort_request
			= kernel.trace("block_rq_abort") ?
{
	name = "elv_abort_request"
	elevator_name = kernel_string(
		@choose_defined($q->elevator->type->elevator_name,
			@choose_defined($q->elevator->elevator_type->elevator_name,
                                        $q->elevator->elevator_name)), "")
	rq = $rq

	if ($rq == 0 || $rq->rq_disk ==0) {
		disk_major = -1
		disk_minor = -1
	}
	else {
		disk_major = $rq->rq_disk->major
		disk_minor = $rq->rq_disk->first_minor
	}

	rq_flags = ($rq == 0) ? 0
		: @choose_defined($rq->cmd_flags, $rq->flags)
}

/**
 * probe ioscheduler_trace.plug - Fires when a request queue is plugged;
 *		ie, requests in the queue cannot be serviced by block driver.
 * @name	: Name of the probe point
 * @rq_queue	: request queue
 *
 */
probe ioscheduler_trace.plug = kernel.trace("block_plug") ?
{
	name = "plug"
	rq_queue = $q
}

/**
 * probe ioscheduler_trace.unplug_io - Fires when a request queue is unplugged;
 *	Either, when number of pending requests in the queue exceeds threshold
 *	or, upon expiration of timer that was activated when queue was plugged.
 * @name	: Name of the probe point
 * @rq_queue	: request queue
 *
 */
probe ioscheduler_trace.unplug_io = kernel.trace("block_unplug_io") ?
{
	name = "unplug_io"
	rq_queue = $q
}

/**
 * probe ioscheduler_trace.unplug_timer - Fires when unplug timer associated
 *					with a request queue expires.
 * @name	: Name of the probe point
 * @rq_queue	: request queue
 *
 */
probe ioscheduler_trace.unplug_timer = kernel.trace("block_unplug_timer") ?
{
	name = "unplug_timer"
	rq_queue = $q
}

function disk_major_from_request:long(var_q:long)
%{ /* pure */
	struct request_queue *q = (struct request_queue *)((uintptr_t)STAP_ARG_var_q);

	/* We need to make sure there isn't a deref hazard here when
	 * reading 'q->queue_head'.  However, kread() wants a pointer to
	 * a pointer, and we can't provide that for 'q->queue_head'
	 * since the list_head structure is directly embedded in the
	 * 'struct request_queue'.  So, we validate all the members of
	 * the list_head structure instead. */
	(void) kread(&(q->queue_head.next));
	(void) kread(&(q->queue_head.prev));
	if (list_empty(&(q->queue_head)))
		STAP_RETVALUE = -1;
	else  {
		struct request *rq = list_entry_rq(q->queue_head.next);
		struct gendisk *rq_disk = kread(&(rq->rq_disk));
		STAP_RETVALUE = kread(&(rq_disk->major));
	}
	CATCH_DEREF_FAULT();
%}

function disk_minor_from_request:long(var_q:long)
%{ /* pure */
	struct request_queue *q = (struct request_queue *)((uintptr_t)STAP_ARG_var_q);

	/* We need to make sure there isn't a deref hazard here when
	 * reading 'q->queue_head'.  However, kread() wants a pointer to
	 * a pointer, and we can't provide that for 'q->queue_head'
	 * since the list_head structure is directly embedded in the
	 * 'struct request_queue'.  So, we validate all the members of
	 * the list_head structure instead. */
	(void) kread(&(q->queue_head.next));
	(void) kread(&(q->queue_head.prev));
	if (list_empty(&(q->queue_head)))
		STAP_RETVALUE = -1;
	else  {
		struct request *rq = list_entry_rq(q->queue_head.next);
		struct gendisk *rq_disk = kread(&(rq->rq_disk));
		STAP_RETVALUE = kread(&(rq_disk->first_minor));
	}
	CATCH_DEREF_FAULT();
%}