[PATCH 02/15] scsi: add scsi_{get,put}_internal_cmd() helper

[Hannes Reinecke <hare@suse.de>]

Add helper functions to allow LLDDs to allocate and free
internal commands.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/scsi_lib.c    | 44 ++++++++++++++++++++++++++++++++++++++
 include/scsi/scsi_device.h |  3 +++
 2 files changed, 47 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 621d841d819a..6fbd36c9c416 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1957,6 +1957,50 @@ void scsi_mq_destroy_tags(struct Scsi_Host *shost)
 	blk_mq_free_tag_set(&shost->tag_set);
 }
 
+/**
+ * scsi_get_internal_cmd - allocate an internal SCSI command
+ * @sdev: SCSI device from which to allocate the command
+ * @data_direction: Data direction for the allocated command
+ * @nowait: do not wait for command allocation to succeed.
+ *
+ * Allocates a SCSI command for internal LLDD use.
+ */
+struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev,
+	int data_direction, bool nowait)
+{
+	struct request *rq;
+	struct scsi_cmnd *scmd;
+	blk_mq_req_flags_t flags = 0;
+	int op;
+
+	if (nowait)
+		flags |= BLK_MQ_REQ_NOWAIT;
+	op = (data_direction == DMA_TO_DEVICE) ?
+		REQ_OP_DRV_OUT : REQ_OP_DRV_IN;
+	rq = blk_mq_alloc_request(sdev->request_queue, op, flags);
+	if (IS_ERR(rq))
+		return NULL;
+	scmd = blk_mq_rq_to_pdu(rq);
+	scmd->device = sdev;
+	return scmd;
+}
+EXPORT_SYMBOL_GPL(scsi_get_internal_cmd);
+
+/**
+ * scsi_put_internal_cmd - free an internal SCSI command
+ * @scmd: SCSI command to be freed
+ *
+ * Check if @scmd is an internal command, and call
+ * blk_mq_free_request() if true.
+ */
+void scsi_put_internal_cmd(struct scsi_cmnd *scmd)
+{
+	struct request *rq = blk_mq_rq_from_pdu(scmd);
+
+	blk_mq_free_request(rq);
+}
+EXPORT_SYMBOL_GPL(scsi_put_internal_cmd);
+
 /**
  * scsi_device_from_queue - return sdev associated with a request_queue
  * @q: The request queue to return the sdev from
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 5d7204186831..218b541515bf 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -470,6 +470,9 @@ static inline int scsi_execute_req(struct scsi_device *sdev,
 	return scsi_execute(sdev, cmd, data_direction, buffer,
 		bufflen, NULL, sshdr, timeout, retries,  0, 0, resid);
 }
+struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev,
+	int data_direction, bool nowait);
+void scsi_put_internal_cmd(struct scsi_cmnd *scmd);
 extern void sdev_disable_disk_events(struct scsi_device *sdev);
 extern void sdev_enable_disk_events(struct scsi_device *sdev);
 extern int scsi_vpd_lun_id(struct scsi_device *, char *, size_t);
-- 
2.29.2