[PATCH v9 22/29] scsi-multipath: update request for terminal request queuing error

[John Garry]

If we cannot queue a request in scsi_queue_rq(), then we may error out
with an error code which means that the block layer ends the request (and
does not requeue). Such an error scenario would be scsi_device transport
offline.

In this case, we should update the request to deal with when
SCMD_MPATH_IO_STATS and SCMD_MPATH_IO_STATS flags have been set.

Signed-off-by: John Garry <john.garry at linux.dev>
---
 drivers/scsi/scsi_lib.c       |  3 +++
 drivers/scsi/scsi_multipath.c | 35 +++++++++++++++++++++++++++++++++++
 include/scsi/scsi_multipath.h |  5 +++++
 3 files changed, 43 insertions(+)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 13562c0ab48b..a5a2967d17a2 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1996,6 +1996,9 @@ static blk_status_t scsi_queue_rq(struct blk_mq_hw_ctx *hctx,
 			cmd->result = DID_NO_CONNECT << 16;
 		else
 			cmd->result = DID_ERROR << 16;
+
+		if (sdev->scsi_mpath_dev && is_mpath_request(req))
+			scsi_mpath_end_request_no_update(req, ret);
 		/*
 		 * Make sure to release all allocated resources when
 		 * we hit an error, as we will never see this command
diff --git a/drivers/scsi/scsi_multipath.c b/drivers/scsi/scsi_multipath.c
index 93a4545f1dbf..bec6dd94f3be 100644
--- a/drivers/scsi/scsi_multipath.c
+++ b/drivers/scsi/scsi_multipath.c
@@ -614,6 +614,41 @@ bool scsi_mpath_end_request(struct request *req, blk_status_t error,
 	return false;
 }
 
+void scsi_mpath_end_request_no_update(struct request *req, blk_status_t error)
+{
+	struct scsi_cmnd *scmd = blk_mq_rq_to_pdu(req);
+	struct scsi_device *sdev = scmd->device;
+	struct bio *clone = req->bio, *master = clone->bi_private;
+	struct block_device *bi_bdev = master->bi_bdev;
+	unsigned int nr_bytes;
+
+	/* Don't generate error logs if we are going to try another path */
+	if (blk_path_error(error))
+		req->rq_flags |= RQF_QUIET;
+
+	if (scmd->flags & SCMD_MPATH_CNT_ACTIVE) {
+		struct Scsi_Host *shost = sdev->host;
+
+		atomic_dec_if_positive(&shost->mpath_nr_active);
+	}
+
+	if (!(scmd->flags & SCMD_MPATH_IO_STATS))
+		return;
+
+	/*
+	 * blk_rq_bytes() value should never exceed start_bytes, but check in
+	 * case.
+	 */
+	if (scmd->start_bytes > blk_rq_bytes(req))
+		nr_bytes = scmd->start_bytes - blk_rq_bytes(req);
+	else
+		nr_bytes = 0;
+
+	bdev_end_io_acct(bi_bdev, req_op(req),
+			 nr_bytes >> SECTOR_SHIFT,
+			 scmd->start_time);
+}
+
 int __init scsi_multipath_init(void)
 {
 	return class_register(&scsi_mpath_device_class);
diff --git a/include/scsi/scsi_multipath.h b/include/scsi/scsi_multipath.h
index dca1307c9fa4..72ad109a9a81 100644
--- a/include/scsi/scsi_multipath.h
+++ b/include/scsi/scsi_multipath.h
@@ -60,6 +60,7 @@ void scsi_mpath_revalidate_paths(struct scsi_mpath_device *scsi_mpath_dev);
 void scsi_mpath_start_request(struct request *req);
 bool scsi_mpath_end_request(struct request *req, blk_status_t error,
 			       unsigned int nr_bytes);
+void scsi_mpath_end_request_no_update(struct request *req, blk_status_t error);
 #else /* CONFIG_SCSI_MULTIPATH */
 
 struct scsi_mpath_head {
@@ -120,5 +121,9 @@ static inline bool scsi_mpath_end_request(struct request *req, blk_status_t erro
 {
 	return false;
 }
+static inline void scsi_mpath_end_request_no_update(struct request *req,
+				blk_status_t error)
+{
+}
 #endif /* CONFIG_SCSI_MULTIPATH */
 #endif /* _SCSI_SCSI_MULTIPATH_H */
-- 
2.43.0