[PATCH v2] nvme: call nvme_complete_rq on NVME_MPATH failures

[jsmart2021@gmail.com (James Smart)]

When an io is rejected by nvmf_check_ready() due to validation of
the controller state, the nvmf_fail_nonready_command() will normally
return BLK_STS_RESOURCE to requeue and retry. However, if the
controller is dying or the io is marked for NVME multipath, the io
is failed so that the controller can terminate or so that the io can
be issued on a different path. Unfortunately, as this reject point
is before the transport has accepted the command, blk-mq ends up
completing the io and never calls nvme_complete_rq(), which is where
multipath may preserve/re-route the io. The end result is, the device
user ends up seeing an EIO error.

Example: single path connectivity, controller is under load, and a
reset is induced. An i/o is received: a) while the reset state has
been set but the queues have yet to be stopped; or b) after queues
are started (at end of reset) but before the reconnect has completed.
The io finishes with an EIO status.

This patch makes the following changes:
- Adds the HOST_PATH_ERROR pathing status from TP4028
- Modifies the reject point such that it appears to queue successfully,
  but actually completes the io with the new pathing status and calls
  nvme_complete_rq().
- nvme_complete_rq() recognizes the new status, avoids resetting the
  controller (likely was already done in order to get this new status),
  and calls the multipather to clear the current path that errored.
  This allows the next command (retry or new command) to select a new
  path if there is one.

Signed-off-by: James Smart <jsmart2021 at gmail.com>
---
 drivers/nvme/host/fabrics.c   | 7 +++++--
 drivers/nvme/host/multipath.c | 7 +++++++
 include/linux/nvme.h          | 1 +
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/fabrics.c b/drivers/nvme/host/fabrics.c
index 206d63cb1afc..bcd09d3a44da 100644
--- a/drivers/nvme/host/fabrics.c
+++ b/drivers/nvme/host/fabrics.c
@@ -552,8 +552,11 @@ blk_status_t nvmf_fail_nonready_command(struct nvme_ctrl *ctrl,
 	    ctrl->state != NVME_CTRL_DEAD &&
 	    !blk_noretry_request(rq) && !(rq->cmd_flags & REQ_NVME_MPATH))
 		return BLK_STS_RESOURCE;
-	nvme_req(rq)->status = NVME_SC_ABORT_REQ;
-	return BLK_STS_IOERR;
+
+	nvme_req(rq)->status = NVME_SC_HOST_PATH_ERROR;
+	blk_mq_start_request(rq);
+	nvme_complete_rq(rq);
+	return BLK_STS_OK;
 }
 EXPORT_SYMBOL_GPL(nvmf_fail_nonready_command);
 
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 5a9562881d4e..b285648c3a7f 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -77,6 +77,13 @@ void nvme_failover_req(struct request *req)
 			queue_work(nvme_wq, &ns->ctrl->ana_work);
 		}
 		break;
+	case NVME_SC_HOST_PATH_ERROR:
+		/*
+		 * Temporary transport disruption in talking to the controller.
+		 * Try to send on a new path.
+		 */
+		nvme_mpath_clear_current_path(ns);
+		break;
 	default:
 		/*
 		 * Reset the controller for any non-ANA error as we don't know
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 68e91ef5494c..818dbe9331be 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -1241,6 +1241,7 @@ enum {
 	NVME_SC_ANA_PERSISTENT_LOSS	= 0x301,
 	NVME_SC_ANA_INACCESSIBLE	= 0x302,
 	NVME_SC_ANA_TRANSITION		= 0x303,
+	NVME_SC_HOST_PATH_ERROR		= 0x370,
 
 	NVME_SC_DNR			= 0x4000,
 };
-- 
2.13.1