[PATCH 10/24] scsi-multipath: add scsi_mpath_{start,end}_request()

[John Garry]

Add scsi_mpath_{start,end}_request() to handle updating private multipath
request data, like nvme_mpath_{start,end}_request().

Since we may need to update mpath_disk data, add a callbacks in
scsi_driver to actually do this work for the scsi driver.

Signed-off-by: John Garry <john.g.garry at oracle.com>
---
 drivers/scsi/scsi_lib.c       |  4 ++++
 include/scsi/scsi_driver.h    |  2 ++
 include/scsi/scsi_multipath.h | 24 ++++++++++++++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 7ed0defc8161e..61179caa7b2c8 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -654,6 +654,8 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
 	 */
 	destroy_rcu_head(&cmd->rcu);
 
+	scsi_mpath_end_request(req);
+
 	/*
 	 * In the MQ case the command gets freed by __blk_mq_end_request,
 	 * so we have to do all cleanup that depends on it earlier.
@@ -1887,6 +1889,8 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 	memset(cmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
 	cmd->submitter = SUBMITTED_BY_BLOCK_LAYER;
 
+	scsi_mpath_start_request(req);
+
 	blk_mq_start_request(req);
 	if (blk_mq_is_reserved_rq(req)) {
 		reason = shost->hostt->queue_reserved_command(shost, cmd);
diff --git a/include/scsi/scsi_driver.h b/include/scsi/scsi_driver.h
index 85e792dc4db50..44e50229a75e7 100644
--- a/include/scsi/scsi_driver.h
+++ b/include/scsi/scsi_driver.h
@@ -20,6 +20,8 @@ struct scsi_driver {
 	int (*eh_action)(struct scsi_cmnd *, int);
 	void (*eh_reset)(struct scsi_cmnd *);
 	#ifdef CONFIG_SCSI_MULTIPATH
+	void (*mpath_start_cmd)(struct scsi_cmnd *);
+	void (*mpath_end_cmd)(struct scsi_cmnd *);
 	struct mpath_disk *(*to_mpath_disk)(struct request *);
 	#endif
 };
diff --git a/include/scsi/scsi_multipath.h b/include/scsi/scsi_multipath.h
index 07db217edb085..6cb3107260952 100644
--- a/include/scsi/scsi_multipath.h
+++ b/include/scsi/scsi_multipath.h
@@ -56,6 +56,23 @@ void scsi_mpath_add_sysfs_link(struct scsi_device *sdev);
 void scsi_mpath_remove_sysfs_link(struct scsi_device *sdev);
 int scsi_mpath_get_head(struct scsi_mpath_head *);
 void scsi_mpath_put_head(struct scsi_mpath_head *);
+
+static inline void scsi_mpath_start_request(struct request *req)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
+
+	if (is_mpath_request(req))
+		scsi_cmd_to_driver(cmd)->mpath_start_cmd(cmd);
+}
+
+static inline void scsi_mpath_end_request(struct request *req)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
+
+	if (is_mpath_request(req))
+		scsi_cmd_to_driver(cmd)->mpath_start_cmd(cmd);
+}
+
 #else /* CONFIG_SCSI_MULTIPATH */
 
 struct scsi_mpath_head {
@@ -104,6 +121,13 @@ static inline void scsi_mpath_put_head(struct scsi_mpath_head *)
 {
 }
 
+static inline void scsi_mpath_start_request(struct request *)
+{
+}
+static inline void scsi_mpath_end_request(struct request *)
+{
+}
+
 static inline void scsi_mpath_add_sysfs_link(struct scsi_device *sdev)
 {
 }
-- 
2.43.5