[PATCH RFC 2/2] libata: Use scsi cmnd budget token for qc tag for SAS host

John Garry
2022-03-15T10:49:34Z

For attaining a qc tag for a SAS host we need to allocate a bit in
ata_port.sas_tag_allocated bitmap.

However we already have a unique tag per device in range
[0, ATA_MAX_QUEUE) in the scsi cmnd budget token, so just use that
instead.

Signed-off-by: John Garry <john.garry@huawei.com>
---
drivers/ata/libata-core.c | 5 +++--
drivers/ata/libata-sata.c | 21 ++++-----------------
drivers/ata/libata-scsi.c | 2 +-
drivers/ata/libata.h | 4 ++--
include/linux/libata.h | 1 -
5 files changed, 10 insertions(+), 23 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 0c854aebfe0b..2c0a550d3ecd 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4572,8 +4572,9 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
* None.
*/

-struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag)
+struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, struct scsi_cmnd *scmd)
{
+ int tag = scsi_cmd_to_rq(scmd)->tag;
struct ata_port *ap = dev->link->ap;
struct ata_queued_cmd *qc;

@@ -4583,7 +4584,7 @@ struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag)

/* libsas case */
if (ap->flags & ATA_FLAG_SAS_HOST) {
- tag = ata_sas_allocate_tag(ap);
+ tag = ata_sas_allocate_tag(ap, scmd);
if (tag < 0)
return NULL;
}
diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
index 071158c0c44c..a4374fdffc43 100644
--- a/drivers/ata/libata-sata.c
+++ b/drivers/ata/libata-sata.c
@@ -1268,29 +1268,16 @@ int ata_sas_queuecmd(struct scsi_cmnd *cmd, struct ata_port *ap)
}
EXPORT_SYMBOL_GPL(ata_sas_queuecmd);

-int ata_sas_allocate_tag(struct ata_port *ap)
+int ata_sas_allocate_tag(struct ata_port *ap, struct scsi_cmnd *scmd)
{
- unsigned int max_queue = ap->host->n_tags;
- unsigned int i, tag;
+ if (scmd->budget_token >= ATA_MAX_QUEUE)
+ return -1;

- for (i = 0, tag = ap->sas_last_tag + 1; i < max_queue; i++, tag++) {
- tag = tag < max_queue ? tag : 0;
-
- /* the last tag is reserved for internal command. */
- if (ata_tag_internal(tag))
- continue;
-
- if (!test_and_set_bit(tag, &ap->sas_tag_allocated)) {
- ap->sas_last_tag = tag;
- return tag;
- }
- }
- return -1;
+ return scmd->budget_token;
}

void ata_sas_free_tag(unsigned int tag, struct ata_port *ap)
{
- clear_bit(tag, &ap->sas_tag_allocated);
}

/**
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index ed8be585a98f..45d63a2ba3ee 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -640,7 +640,7 @@ static struct ata_queued_cmd *ata_scsi_qc_new(struct ata_device *dev,
{
struct ata_queued_cmd *qc;

- qc = ata_qc_new_init(dev, scsi_cmd_to_rq(cmd)->tag);
+ qc = ata_qc_new_init(dev, cmd);
if (qc) {
qc->scsicmd = cmd;
qc->scsidone = scsi_done;
diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
index 51e01acdd241..65302d7829fe 100644
--- a/drivers/ata/libata.h
+++ b/drivers/ata/libata.h
@@ -44,7 +44,7 @@ static inline void ata_force_cbl(struct ata_port *ap) { }
#endif
extern u64 ata_tf_to_lba(const struct ata_taskfile *tf);
extern u64 ata_tf_to_lba48(const struct ata_taskfile *tf);
-extern struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag);
+extern struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, struct scsi_cmnd *scmd);
extern int ata_build_rw_tf(struct ata_taskfile *tf, struct ata_device *dev,
u64 block, u32 n_block, unsigned int tf_flags,
unsigned int tag, int class);
@@ -93,7 +93,7 @@ extern unsigned int ata_read_log_page(struct ata_device *dev, u8 log,

/* libata-sata.c */
#ifdef CONFIG_SATA_HOST
-int ata_sas_allocate_tag(struct ata_port *ap);
+int ata_sas_allocate_tag(struct ata_port *ap, struct scsi_cmnd *scmd);
void ata_sas_free_tag(unsigned int tag, struct ata_port *ap);
#else
static inline int ata_sas_allocate_tag(struct ata_port *ap)
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 7f99b4d78822..3b9399f67b39 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -814,7 +814,6 @@ struct ata_port {
unsigned int cbl; /* cable type; ATA_CBL_xxx */

struct ata_queued_cmd qcmd[ATA_MAX_QUEUE + 1];
- unsigned long sas_tag_allocated; /* for sas tag allocation only */
u64 qc_active;
int nr_active_links; /* #links with active qcs */
unsigned int sas_last_tag; /* track next tag hw expects */
--
2.26.2