scsi: libsas: Add sas_task_find_rq()

blk-mq already provides a unique tag per request. Some libsas LLDDs - like
hisi_sas - already use this tag as the unique per-I/O HW tag.

Add a common function to provide the request associated with a sas_task for
all libsas LLDDs.
Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1666091763-11023-2-git-send-email-john.garry@huawei.comReviewed-by: Jack Wang <jinpu.wang@ionos.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

include/scsi/libsas.h

@@ -644,6 +644,24 @@ static inline bool sas_is_internal_abort(struct sas_task *task)
 	return task->task_proto == SAS_PROTOCOL_INTERNAL_ABORT;
 }
 
+static inline struct request *sas_task_find_rq(struct sas_task *task)
+{
+	struct scsi_cmnd *scmd;
+
+	if (task->task_proto & SAS_PROTOCOL_STP_ALL) {
+		struct ata_queued_cmd *qc = task->uldd_task;
+
+		scmd = qc ? qc->scsicmd : NULL;
+	} else {
+		scmd = task->uldd_task;
+	}
+
+	if (!scmd)
+		return NULL;
+
+	return scsi_cmd_to_rq(scmd);
+}
+
 struct sas_domain_function_template {
 	/* The class calls these to notify the LLDD of an event. */
 	void (*lldd_port_formed)(struct asd_sas_phy *);