Commit 31cc23b3 authored by Tejun Heo's avatar Tejun Heo Committed by Jeff Garzik
Browse files

libata-pmp-prep: implement ops->qc_defer() 



Controllers which support PMP have various restrictions on which
combinations of commands are allowed to what number of devices
concurrently.  This patch implements ops->qc_defer() which determines
whether a qc can be issued at the moment or should be deferred.

If the function returns ATA_DEFER_LINK, the qc will be deferred until
a qc completes on the link.  If ATA_DEFER_PORT, until a qc completes
on any link.  The defer conditions are advisory and in general
ATA_DEFER_LINK can be considered as lower priority deferring than
ATA_DEFER_PORT.

ops->qc_defer() replaces fixed ata_scmd_need_defer().  For standard
NCQ/non-NCQ exclusion, ata_std_qc_defer() is implemented.  ahci and
sata_sil24 are converted to use ata_std_qc_defer().

ops->qc_defer() is heavier than the original mechanism because full qc
is prepped before determining to defer it, but various information is
needed to determine defer conditinos and fully translating a qc is the
only way to supply such information in generic manner.

IMHO, this shouldn't cause any noticeable performance issues as

* for most cases deferring occurs rarely (except for NCQ-aware
  cmd-switching PMP)
* translation itself isn't that expensive
* once deferred the command won't be repeated until another command
  completes which usually is a very long time cpu-wise.

Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarJeff Garzik <jeff@garzik.org>
parent fb7fd614

drivers/ata/ahci.c

+2 −0
Original line number Diff line number Diff line
@@ -268,6 +268,7 @@ static const struct ata_port_operations ahci_ops = { 


	.tf_read		= ahci_tf_read,



	.qc_defer		= ata_std_qc_defer,

	.qc_prep		= ahci_qc_prep,

	.qc_issue		= ahci_qc_issue,
@@ -298,6 +299,7 @@ static const struct ata_port_operations ahci_vt8251_ops = { 


	.tf_read		= ahci_tf_read,



	.qc_defer		= ata_std_qc_defer,

	.qc_prep		= ahci_qc_prep,

	.qc_issue		= ahci_qc_issue,

drivers/ata/libata-core.c

+31 −0
Original line number Diff line number Diff line
@@ -4345,6 +4345,36 @@ int ata_check_atapi_dma(struct ata_queued_cmd *qc) 
	return 0;

}



/**

 *	ata_std_qc_defer - Check whether a qc needs to be deferred

 *	@qc: ATA command in question

 *

 *	Non-NCQ commands cannot run with any other command, NCQ or

 *	not.  As upper layer only knows the queue depth, we are

 *	responsible for maintaining exclusion.  This function checks

 *	whether a new command @qc can be issued.

 *

 *	LOCKING:

 *	spin_lock_irqsave(host lock)

 *

 *	RETURNS:

 *	ATA_DEFER_* if deferring is needed, 0 otherwise.

 */

int ata_std_qc_defer(struct ata_queued_cmd *qc)

{

	struct ata_link *link = qc->dev->link;



	if (qc->tf.protocol == ATA_PROT_NCQ) {

		if (!ata_tag_valid(link->active_tag))

			return 0;

	} else {

		if (!ata_tag_valid(link->active_tag) && !link->sactive)

			return 0;

	}



	return ATA_DEFER_LINK;

}



/**

 *	ata_qc_prep - Prepare taskfile for submission

 *	@qc: Metadata associated with taskfile to be prepared
@@ -7111,6 +7141,7 @@ EXPORT_SYMBOL_GPL(ata_interrupt); 
EXPORT_SYMBOL_GPL(ata_do_set_mode);

EXPORT_SYMBOL_GPL(ata_data_xfer);

EXPORT_SYMBOL_GPL(ata_data_xfer_noirq);

EXPORT_SYMBOL_GPL(ata_std_qc_defer);

EXPORT_SYMBOL_GPL(ata_qc_prep);

EXPORT_SYMBOL_GPL(ata_dumb_qc_prep);

EXPORT_SYMBOL_GPL(ata_noop_qc_prep);

drivers/ata/libata-scsi.c

+26 −36
Original line number Diff line number Diff line
@@ -749,6 +749,13 @@ static void ata_scsi_sdev_config(struct scsi_device *sdev) 
{

	sdev->use_10_for_rw = 1;

	sdev->use_10_for_ms = 1;



	/* Schedule policy is determined by ->qc_defer() callback and

	 * it needs to see every deferred qc.  Set dev_blocked to 1 to

	 * prevent SCSI midlayer from automatically deferring

	 * requests.

	 */

	sdev->max_device_blocked = 1;

}



static void ata_scsi_dev_config(struct scsi_device *sdev,
@@ -1415,37 +1422,6 @@ static void ata_scsi_qc_complete(struct ata_queued_cmd *qc) 
	ata_qc_free(qc);

}



/**

 *	ata_scmd_need_defer - Check whether we need to defer scmd

 *	@dev: ATA device to which the command is addressed

 *	@is_io: Is the command IO (and thus possibly NCQ)?

 *

 *	NCQ and non-NCQ commands cannot run together.  As upper layer

 *	only knows the queue depth, we are responsible for maintaining

 *	exclusion.  This function checks whether a new command can be

 *	issued to @dev.

 *

 *	LOCKING:

 *	spin_lock_irqsave(host lock)

 *

 *	RETURNS:

 *	1 if deferring is needed, 0 otherwise.

 */

static int ata_scmd_need_defer(struct ata_device *dev, int is_io)

{

	struct ata_link *link = dev->link;

	int is_ncq = is_io && ata_ncq_enabled(dev);



	if (is_ncq) {

		if (!ata_tag_valid(link->active_tag))

			return 0;

	} else {

		if (!ata_tag_valid(link->active_tag) && !link->sactive)

			return 0;

	}

	return 1;

}



/**

 *	ata_scsi_translate - Translate then issue SCSI command to ATA device

 *	@dev: ATA device to which the command is addressed
@@ -1477,14 +1453,12 @@ static int ata_scsi_translate(struct ata_device *dev, struct scsi_cmnd *cmd, 
			      void (*done)(struct scsi_cmnd *),

			      ata_xlat_func_t xlat_func)

{

	struct ata_port *ap = dev->link->ap;

	struct ata_queued_cmd *qc;

	int is_io = xlat_func == ata_scsi_rw_xlat;

	int rc;



	VPRINTK("ENTER\n");



	if (unlikely(ata_scmd_need_defer(dev, is_io)))

		goto defer;



	qc = ata_scsi_qc_new(dev, cmd, done);

	if (!qc)

		goto err_mem;
@@ -1508,6 +1482,11 @@ static int ata_scsi_translate(struct ata_device *dev, struct scsi_cmnd *cmd, 
	if (xlat_func(qc))

		goto early_finish;



	if (ap->ops->qc_defer) {

		if ((rc = ap->ops->qc_defer(qc)))

			goto defer;

	}



	/* select device, send command to hardware */

	ata_qc_issue(qc);
@@ -1529,8 +1508,12 @@ err_mem: 
	return 0;



defer:

	ata_qc_free(qc);

	DPRINTK("EXIT - defer\n");

	if (rc == ATA_DEFER_LINK)

		return SCSI_MLQUEUE_DEVICE_BUSY;

	else

		return SCSI_MLQUEUE_HOST_BUSY;

}



/**
@@ -3034,6 +3017,13 @@ int ata_scsi_add_hosts(struct ata_host *host, struct scsi_host_template *sht) 
		shost->max_channel = 1;

		shost->max_cmd_len = 16;



		/* Schedule policy is determined by ->qc_defer()

		 * callback and it needs to see every deferred qc.

		 * Set host_blocked to 1 to prevent SCSI midlayer from

		 * automatically deferring requests.

		 */

		shost->max_host_blocked = 1;



		rc = scsi_add_host(ap->scsi_host, ap->host->dev);

		if (rc)

			goto err_add;

drivers/ata/sata_nv.c

+1 −0
Original line number Diff line number Diff line
@@ -423,6 +423,7 @@ static const struct ata_port_operations nv_adma_ops = { 
	.bmdma_start		= ata_bmdma_start,

	.bmdma_stop		= ata_bmdma_stop,

	.bmdma_status		= ata_bmdma_status,

	.qc_defer		= ata_std_qc_defer,

	.qc_prep		= nv_adma_qc_prep,

	.qc_issue		= nv_adma_qc_issue,

	.freeze			= nv_adma_freeze,

drivers/ata/sata_sil24.c

+1 −0
Original line number Diff line number Diff line
@@ -393,6 +393,7 @@ static const struct ata_port_operations sil24_ops = { 


	.tf_read		= sil24_tf_read,



	.qc_defer		= ata_std_qc_defer,

	.qc_prep		= sil24_qc_prep,

	.qc_issue		= sil24_qc_issue,

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