diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
index e3adc008fed1..7e889534d73b 100644
--- a/drivers/ata/libata-pmp.c
+++ b/drivers/ata/libata-pmp.c
@@ -110,13 +110,24 @@ int sata_pmp_qc_defer_cmd_switch(struct ata_queued_cmd *qc)
 {
 	struct ata_link *link = qc->dev->link;
 	struct ata_port *ap = link->ap;
+	int ret;
 
 	if (ap->excl_link == NULL || ap->excl_link == link) {
 		if (ap->nr_active_links == 0 || ata_link_active(link)) {
 			qc->flags |= ATA_QCFLAG_CLEAR_EXCL;
-			return ata_std_qc_defer(qc);
+			ret = ata_std_qc_defer(qc);
+			if (ret == ATA_DEFER_LINK)
+				return ATA_DEFER_LINK_EXCL;
+			return ret;
 		}
 
+		/*
+		 * Note: ap->excl_link contains the link that is next in line,
+		 * i.e. implicit round robin. If there is only one link
+		 * dispatching, ap->excl_link will be left unclaimed, allowing
+		 * other links to set ap->excl_link, ensuring that the currently
+		 * active link cannot queue any more.
+		 */
 		ap->excl_link = link;
 	}
 
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index f03b6326ad2d..ca29744c57f9 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1787,6 +1787,14 @@ static int ata_scsi_qc_issue(struct ata_port *ap, struct ata_queued_cmd *qc)
 	case ATA_DEFER_LINK:
 		ret = SCSI_MLQUEUE_DEVICE_BUSY;
 		goto defer_qc;
+	case ATA_DEFER_LINK_EXCL:
+		/*
+		 * Drivers making use of ap->excl_link cannot store the QC in
+		 * ap->deferred_qc, because the ap->excl_link handling is
+		 * incompatible with the ap->deferred_qc workqueue handling.
+		 */
+		ret = SCSI_MLQUEUE_DEVICE_BUSY;
+		goto free_qc;
 	case ATA_DEFER_PORT:
 		ret = SCSI_MLQUEUE_HOST_BUSY;
 		goto free_qc;
diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index d642ece9f07a..57f1081b86db 100644
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -789,6 +789,7 @@ static int sil24_qc_defer(struct ata_queued_cmd *qc)
 	struct ata_link *link = qc->dev->link;
 	struct ata_port *ap = link->ap;
 	u8 prot = qc->tf.protocol;
+	int ret;
 
 	/*
 	 * There is a bug in the chip:
@@ -826,7 +827,10 @@ static int sil24_qc_defer(struct ata_queued_cmd *qc)
 		qc->flags |= ATA_QCFLAG_CLEAR_EXCL;
 	}
 
-	return ata_std_qc_defer(qc);
+	ret = ata_std_qc_defer(qc);
+	if (ret == ATA_DEFER_LINK)
+		return ATA_DEFER_LINK_EXCL;
+	return ret;
 }
 
 static enum ata_completion_errors sil24_qc_prep(struct ata_queued_cmd *qc)
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 5c085ef4eda7..360776016b50 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -371,6 +371,7 @@ enum {
 	/* return values for ->qc_defer */
 	ATA_DEFER_LINK		= 1,
 	ATA_DEFER_PORT		= 2,
+	ATA_DEFER_LINK_EXCL	= 3,
 
 	/* desc_len for ata_eh_info and context */
 	ATA_EH_DESC_LEN		= 80,