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From: Mike Snitzer <>
To: Christoph Hellwig <>, Jens Axboe <>
Subject: [PATCH v4 3/3] nvme: decouple basic ANA log page re-read support from native multipathing
Date: Fri, 16 Apr 2021 19:53:29 -0400
Message-ID: <> (raw)
In-Reply-To: <>

Whether or not ANA is present is a choice of the target implementation;
the host (and whether it supports multipathing) has _zero_ influence on
this. If the target declares a path as 'inaccessible' the path _is_
inaccessible to the host. As such, ANA support should be functional
even if native multipathing is not.

Introduce ability to always re-read ANA log page as required due to ANA
error and make current ANA state available via sysfs -- even if native
multipathing is disabled on the host (e.g. nvme_core.multipath=N).
This is achieved by factoring out nvme_update_ana() and calling it in
nvme_complete_rq() for all FAILOVER requests.

This affords userspace access to the current ANA state independent of
which layer might be doing multipathing. This makes 'nvme list-subsys'
show ANA state for all NVMe subsystems with multiple controllers. It
also allows userspace multipath-tools to rely on the NVMe driver for
ANA support while dm-multipath takes care of multipathing.

And as always, if embedded NVMe users do not want any performance
overhead associated with ANA or native NVMe multipathing they can

Signed-off-by: Mike Snitzer <>
 drivers/nvme/host/core.c      |  2 ++
 drivers/nvme/host/multipath.c | 16 +++++++++++-----
 drivers/nvme/host/nvme.h      |  4 ++++
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index a12b10a1383c..83ca96292157 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -340,6 +340,8 @@ static inline void nvme_end_req(struct request *req)
 static inline void nvme_failup_req(struct request *req)
+	nvme_update_ana(req);
 	nvme_req(req)->status = NVME_SC_HOST_PATH_ERROR;
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index a1d476e1ac02..7d94250264aa 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -65,23 +65,29 @@ void nvme_set_disk_name(char *disk_name, struct nvme_ns *ns,
-void nvme_failover_req(struct request *req)
+void nvme_update_ana(struct request *req)
 	struct nvme_ns *ns = req->q->queuedata;
 	u16 status = nvme_req(req)->status & 0x7ff;
-	unsigned long flags;
-	nvme_mpath_clear_current_path(ns);
 	 * If we got back an ANA error, we know the controller is alive but not
-	 * ready to serve this namespace.  Kick of a re-read of the ANA
+	 * ready to serve this namespace.  Kick off a re-read of the ANA
 	 * information page, and just try any other available path for now.
 	if (nvme_is_ana_error(status) && ns->ctrl->ana_log_buf) {
 		set_bit(NVME_NS_ANA_PENDING, &ns->flags);
 		queue_work(nvme_wq, &ns->ctrl->ana_work);
+void nvme_failover_req(struct request *req)
+	struct nvme_ns *ns = req->q->queuedata;
+	unsigned long flags;
+	nvme_mpath_clear_current_path(ns);
+	nvme_update_ana(req);
 	spin_lock_irqsave(&ns->head->requeue_lock, flags);
 	blk_steal_bios(&ns->head->requeue_list, req);
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 07b34175c6ce..4eed8536625c 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -664,6 +664,7 @@ void nvme_mpath_start_freeze(struct nvme_subsystem *subsys);
 void nvme_set_disk_name(char *disk_name, struct nvme_ns *ns,
 			struct nvme_ctrl *ctrl, int *flags);
 void nvme_failover_req(struct request *req);
+void nvme_update_ana(struct request *req);
 void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl);
 int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl,struct nvme_ns_head *head);
 void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id);
@@ -714,6 +715,9 @@ static inline void nvme_set_disk_name(char *disk_name, struct nvme_ns *ns,
 static inline void nvme_failover_req(struct request *req)
+static inline void nvme_update_ana(struct request *req)
 static inline void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl)

  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 23:53 [PATCH v3 0/4] nvme: improve error handling and ana_state to work well with dm-multipath Mike Snitzer
2021-04-16 23:53 ` [PATCH v4 1/3] nvme: return BLK_STS_DO_NOT_RETRY if the DNR bit is set Mike Snitzer
2021-04-20  9:34   ` Christoph Hellwig
2021-04-16 23:53 ` [PATCH v4 2/3] nvme: allow local retry and proper failover for REQ_FAILFAST_TRANSPORT Mike Snitzer
2021-04-16 23:53 ` Mike Snitzer [this message]
2021-04-20  9:34   ` [PATCH v4 3/3] nvme: decouple basic ANA log page re-read support from native multipathing Christoph Hellwig
2021-04-20 14:17     ` Mike Snitzer
2021-04-17  0:02 ` [PATCH v4 0/4] nvme: improve error handling and ana_state to work well with dm-multipath Mike Snitzer
2021-04-19 14:56   ` Mike Snitzer
2021-04-20  9:37 ` [PATCH v3 " Christoph Hellwig
2021-04-20 14:38   ` Mike Snitzer
2021-04-20 15:46     ` Laurence Oberman
2021-05-01 11:58       ` Hannes Reinecke
2021-05-01 15:19         ` Mike Snitzer

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