[PATCH v7 06/28] scsi: core: Add scsi_{get,put}_internal_cmd() helpers

[Bart Van Assche <bvanassche@acm.org>]

From: Hannes Reinecke <hare@suse.de>

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

Reviewed-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
[ bvanassche: changed the 'nowait' argument into a 'flags' argument. See also
  https://lore.kernel.org/linux-scsi/20211125151048.103910-3-hare@suse.de/ ]
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/scsi/scsi_lib.c    | 38 ++++++++++++++++++++++++++++++++++++++
 include/scsi/scsi_device.h |  4 ++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d4e874bbf2ea..51ad2ad07e43 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2134,6 +2134,44 @@ void scsi_mq_free_tags(struct kref *kref)
 	complete(&shost->tagset_freed);
 }
 
+/**
+ * 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
+ * @flags: request allocation flags, e.g. BLK_MQ_REQ_RESERVED or
+ *	BLK_MQ_REQ_NOWAIT.
+ *
+ * Allocates a SCSI command for internal LLDD use.
+ */
+struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev,
+					enum dma_data_direction data_direction,
+					blk_mq_req_flags_t flags)
+{
+	enum req_op op = data_direction == DMA_TO_DEVICE ? REQ_OP_DRV_OUT :
+							   REQ_OP_DRV_IN;
+	struct scsi_cmnd *scmd;
+	struct request *rq;
+
+	rq = scsi_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
+ */
+void scsi_put_internal_cmd(struct scsi_cmnd *scmd)
+{
+	blk_mq_free_request(blk_mq_rq_from_pdu(scmd));
+}
+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 918631088711..1e2e599517e9 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -558,6 +558,10 @@ int scsi_execute_cmd(struct scsi_device *sdev, const unsigned char *cmd,
 		     const struct scsi_exec_args *args);
 void scsi_failures_reset_retries(struct scsi_failures *failures);
 
+struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev,
+					enum dma_data_direction data_direction,
+					blk_mq_req_flags_t flags);
+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);