[PATCH V5 07/13] blk-mq: add callbacks for storing & retrieving budget token

[Ming Lei <ming.lei@redhat.com>]

SCSI is the only driver which requires dispatch budget, and it isn't
fair to add one field into 'struct request' for storing budget token
which will be used in the following patches for improving scsi's device
busy scalability.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Tested-by: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/scsi/scsi_lib.c  | 18 ++++++++++++++++++
 include/linux/blk-mq.h   |  9 +++++++++
 include/scsi/scsi_cmnd.h |  2 ++
 3 files changed, 29 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 60c7a7d74852..022ed2991463 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1635,6 +1635,20 @@ static bool scsi_mq_get_budget(struct request_queue *q)
 	return false;
 }
 
+static void scsi_mq_set_rq_budget_token(struct request *req, int token)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
+
+	cmd->budget_token = token;
+}
+
+static int scsi_mq_get_rq_budget_token(struct request *req)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
+
+	return cmd->budget_token;
+}
+
 static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 			 const struct blk_mq_queue_data *bd)
 {
@@ -1845,6 +1859,8 @@ static const struct blk_mq_ops scsi_mq_ops_no_commit = {
 	.cleanup_rq	= scsi_cleanup_rq,
 	.busy		= scsi_mq_lld_busy,
 	.map_queues	= scsi_map_queues,
+	.set_rq_budget_token = scsi_mq_set_rq_budget_token,
+	.get_rq_budget_token = scsi_mq_get_rq_budget_token,
 };
 
 
@@ -1873,6 +1889,8 @@ static const struct blk_mq_ops scsi_mq_ops = {
 	.cleanup_rq	= scsi_cleanup_rq,
 	.busy		= scsi_mq_lld_busy,
 	.map_queues	= scsi_map_queues,
+	.set_rq_budget_token = scsi_mq_set_rq_budget_token,
+	.get_rq_budget_token = scsi_mq_get_rq_budget_token,
 };
 
 struct request_queue *scsi_mq_alloc_queue(struct scsi_device *sdev)
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 794b2a33a2c3..d2c66b453d07 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -316,6 +316,15 @@ struct blk_mq_ops {
 	 */
 	void (*put_budget)(struct request_queue *);
 
+	/*
+	 * @set_rq_budget_toekn: store rq's budget token
+	 */
+	void (*set_rq_budget_token)(struct request *, int);
+	/*
+	 * @get_rq_budget_toekn: retrieve rq's budget token
+	 */
+	int (*get_rq_budget_token)(struct request *);
+
 	/**
 	 * @timeout: Called on request timeout.
 	 */
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 69ade4fb71aa..4884f300c896 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -75,6 +75,8 @@ struct scsi_cmnd {
 
 	int eh_eflags;		/* Used by error handlr */
 
+	int budget_token;
+
 	/*
 	 * This is set to jiffies as it was when the command was first
 	 * allocated.  It is used to time how long the command has
-- 
2.25.4