libata: Improve ATA queued command allocation

Improve ATA queued command allocation as follows:

- 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 -1] in the scsi cmnd budget token, so just use that
  instead.

- It is a bit pointless to have ata_qc_new_init() in libata-core.c since it
  pokes scsi internals, so inline it in ata_scsi_qc_new() (in
  libata-scsi.c). Also update Doc accordingly.

- Use standard SCSI helpers set_host_byte() and set_status_byte() in
  ata_scsi_qc_new().

Christoph Hellwig originally contributed the change to inline
ata_qc_new_init().

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

1 files changed, 1 insertions, 47 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index ca64837641be..23d1dc5faf73 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4567,42 +4567,6 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
 }
 
 /**
- *	ata_qc_new_init - Request an available ATA command, and initialize it
- *	@dev: Device from whom we request an available command structure
- *	@tag: tag
- *
- *	LOCKING:
- *	None.
- */
-
-struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag)
-{
-	struct ata_port *ap = dev->link->ap;
-	struct ata_queued_cmd *qc;
-
-	/* no command while frozen */
-	if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))
-		return NULL;
-
-	/* libsas case */
-	if (ap->flags & ATA_FLAG_SAS_HOST) {
-		tag = ata_sas_allocate_tag(ap);
-		if (tag < 0)
-			return NULL;
-	}
-
-	qc = __ata_qc_from_tag(ap, tag);
-	qc->tag = qc->hw_tag = tag;
-	qc->scsicmd = NULL;
-	qc->ap = ap;
-	qc->dev = dev;
-
-	ata_qc_reinit(qc);
-
-	return qc;
-}
-
-/**
  *	ata_qc_free - free unused ata_queued_cmd
  *	@qc: Command to complete
  *
@@ -4614,19 +4578,9 @@ struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag)
  */
 void ata_qc_free(struct ata_queued_cmd *qc)
 {
-	struct ata_port *ap;
-	unsigned int tag;
-
-	WARN_ON_ONCE(qc == NULL); /* ata_qc_from_tag _might_ return NULL */
-	ap = qc->ap;
-
 	qc->flags = 0;
-	tag = qc->tag;
-	if (ata_tag_valid(tag)) {
+	if (ata_tag_valid(qc->tag))
 		qc->tag = ATA_TAG_POISON;
-		if (ap->flags & ATA_FLAG_SAS_HOST)
-			ata_sas_free_tag(tag, ap);
-	}
 }
 
 void __ata_qc_complete(struct ata_queued_cmd *qc)