1 files changed, 60 insertions, 6 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 622350d9b2e3..0cd3ad497136 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -1712,6 +1712,8 @@ unsigned ata_exec_internal_sg(struct ata_device *dev,
 	else
 		tag = 0;
 
+	if (test_and_set_bit(tag, &ap->qc_allocated))
+		BUG();
 	qc = __ata_qc_from_tag(ap, tag);
 
 	qc->tag = tag;
@@ -4563,6 +4565,37 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
 }
 
 /**
+ *	ata_qc_new - Request an available ATA command, for queueing
+ *	@ap: Port associated with device @dev
+ *	@dev: Device from whom we request an available command structure
+ *
+ *	LOCKING:
+ *	None.
+ */
+
+static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
+{
+	struct ata_queued_cmd *qc = NULL;
+	unsigned int i;
+
+	/* no command while frozen */
+	if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))
+		return NULL;
+
+	/* the last tag is reserved for internal command. */
+	for (i = 0; i < ATA_MAX_QUEUE - 1; i++)
+		if (!test_and_set_bit(i, &ap->qc_allocated)) {
+			qc = __ata_qc_from_tag(ap, i);
+			break;
+		}
+
+	if (qc)
+		qc->tag = i;
+
+	return qc;
+}
+
+/**
  *	ata_qc_new_init - Request an available ATA command, and initialize it
  *	@dev: Device from whom we request an available command structure
  *	@tag: command tag
@@ -4571,20 +4604,16 @@ 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 ata_port *ap = dev->link->ap;
 	struct ata_queued_cmd *qc;
 
-	if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))
-		return NULL;
-
-	qc = __ata_qc_from_tag(ap, tag);
+	qc = ata_qc_new(ap);
 	if (qc) {
 		qc->scsicmd = NULL;
 		qc->ap = ap;
 		qc->dev = dev;
-		qc->tag = tag;
 
 		ata_qc_reinit(qc);
 	}
@@ -4592,6 +4621,31 @@ struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev, int tag)
 	return qc;
 }
 
+/**
+ *	ata_qc_free - free unused ata_queued_cmd
+ *	@qc: Command to complete
+ *
+ *	Designed to free unused ata_queued_cmd object
+ *	in case something prevents using it.
+ *
+ *	LOCKING:
+ *	spin_lock_irqsave(host lock)
+ */
+void ata_qc_free(struct ata_queued_cmd *qc)
+{
+	struct ata_port *ap = qc->ap;
+	unsigned int tag;
+
+	WARN_ON(qc == NULL);	/* ata_qc_from_tag _might_ return NULL */
+
+	qc->flags = 0;
+	tag = qc->tag;
+	if (likely(ata_tag_valid(tag))) {
+		qc->tag = ATA_TAG_POISON;
+		clear_bit(tag, &ap->qc_allocated);
+	}
+}
+
 void __ata_qc_complete(struct ata_queued_cmd *qc)
 {
 	struct ata_port *ap = qc->ap;