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: Tejun Heo <htejun@xxxxxxxxx>
---
drivers/ata/ahci.c | 2 ++
drivers/ata/libata-core.c | 39 +++++++++++++++++++++++++++++++
drivers/ata/libata-scsi.c | 57 +++++++++++++++------------------------------
drivers/ata/sata_sil24.c | 1 +
include/linux/libata.h | 6 +++++
5 files changed, 67 insertions(+), 38 deletions(-)
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 3878dea..d2d43cf 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -251,6 +251,7 @@ static const struct ata_port_operations
.tf_read = ahci_tf_read,
+ .qc_defer = ata_std_qc_defer,
.qc_prep = ahci_qc_prep,
.qc_issue = ahci_qc_issue,
@@ -284,6 +285,7 @@ static const struct ata_port_operations
.tf_read = ahci_tf_read,
+ .qc_defer = ata_std_qc_defer,
.qc_prep = ahci_qc_prep,
.qc_issue = ahci_qc_issue,
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 6b3a013..5f0835d 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3485,6 +3485,37 @@ int ata_check_atapi_dma(struct ata_queue
return rc;
}
+
+/**
+ * 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
@@ -5599,6 +5630,13 @@ static struct ata_port * ata_port_add(co
shost->transportt = &ata_scsi_transport_template;
+ /* 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;
+
ap = ata_shost_to_port(shost);
ata_port_init(ap, host, ent, port_no);
@@ -6299,6 +6337,7 @@ EXPORT_SYMBOL_GPL(ata_interrupt);
EXPORT_SYMBOL_GPL(ata_mmio_data_xfer);
EXPORT_SYMBOL_GPL(ata_pio_data_xfer);
EXPORT_SYMBOL_GPL(ata_pio_data_xfer_noirq);
+EXPORT_SYMBOL_GPL(ata_std_qc_defer);
EXPORT_SYMBOL_GPL(ata_qc_prep);
EXPORT_SYMBOL_GPL(ata_noop_qc_prep);
EXPORT_SYMBOL_GPL(ata_bmdma_setup);
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index feae473..c62992f 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -810,6 +810,13 @@ static void ata_scsi_dev_config(struct s
{
unsigned int max_sectors;
+ /* 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;
+
/* TODO: 2048 is an arbitrary number, not the
* hardware maximum. This should be increased to
* 65534 when Jens Axboe's patch for dynamically
@@ -1500,39 +1507,6 @@ static void ata_scsi_qc_complete(struct
}
/**
- * 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;
-
- if (!(dev->flags & ATA_DFLAG_NCQ))
- return 0;
-
- if (is_io) {
- 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
* @cmd: SCSI command to execute
@@ -1563,15 +1537,13 @@ static int ata_scsi_translate(struct ata
void (*done)(struct scsi_cmnd *),
ata_xlat_func_t xlat_func)
{
+ struct ata_port *ap = dev->link->ap;
struct ata_queued_cmd *qc;
u8 *scsicmd = cmd->cmnd;
- 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;
@@ -1599,6 +1571,11 @@ static int ata_scsi_translate(struct ata
if (xlat_func(qc, scsicmd))
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);
@@ -1620,8 +1597,12 @@ err_mem:
return 0;
defer:
+ ata_qc_free(qc);
DPRINTK("EXIT - defer\n");
- return SCSI_MLQUEUE_DEVICE_BUSY;
+ if (rc == ATA_DEFER_LINK)
+ return SCSI_MLQUEUE_DEVICE_BUSY;
+ else
+ return SCSI_MLQUEUE_HOST_BUSY;
}
/**
diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index 1030496..9564e49 100644
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -396,6 +396,7 @@ static const struct ata_port_operations
.tf_read = sil24_tf_read,
+ .qc_defer = ata_std_qc_defer,
.qc_prep = sil24_qc_prep,
.qc_issue = sil24_qc_issue,
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 1b91a7c..12e866d 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -263,6 +263,10 @@ enum {
/* ering size */
ATA_ERING_SIZE = 32,
+ /* return values for ->qc_defer */
+ ATA_DEFER_LINK = 1,
+ ATA_DEFER_PORT = 2,
+
/* desc_len for ata_eh_info and context */
ATA_EH_DESC_LEN = 80,
@@ -633,6 +637,7 @@ struct ata_port_operations {
void (*data_xfer) (struct ata_device *, unsigned char *, unsigned int, int);
+ int (*qc_defer) (struct ata_queued_cmd *qc);
void (*qc_prep) (struct ata_queued_cmd *qc);
unsigned int (*qc_issue) (struct ata_queued_cmd *qc);
@@ -805,6 +810,7 @@ extern void ata_pio_data_xfer(struct ata
unsigned int buflen, int write_data);
extern void ata_pio_data_xfer_noirq(struct ata_device *adev, unsigned char *buf,
unsigned int buflen, int write_data);
+extern int ata_std_qc_defer(struct ata_queued_cmd *qc);
extern void ata_qc_prep(struct ata_queued_cmd *qc);
extern void ata_noop_qc_prep(struct ata_queued_cmd *qc);
extern unsigned int ata_qc_issue_prot(struct ata_queued_cmd *qc);
--
1.4.2.3
-
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