[PATCH 2/2] nvme: delete disk when last path is gone

[Hannes Reinecke]

The multipath code currently deletes the disk only after all references
to it are dropped rather than when the last path to that disk is lost.
This has been reported to cause problems with some use cases like MD RAID.

This patch implements an alternative behaviour of deleting the disk when
the last path is gone, ie the same behaviour as non-multipathed nvme
devices. The new behaviour will be selected with the 'fail_if_no_path'
attribute, as returning it's arguably the same functionality.

Suggested-by: Keith Busch <kbusch at kernel.org>
Signed-off-by: Hannes Reinecke <hare at suse.de>
---
 drivers/nvme/host/core.c      |  1 +
 drivers/nvme/host/multipath.c |  3 ++-
 drivers/nvme/host/nvme.h      | 17 +++++++++++++++--
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 2fb3ecc0c53b..d717a6283d6e 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -542,6 +542,7 @@ static void nvme_free_ns_head(struct kref *ref)
 		container_of(ref, struct nvme_ns_head, ref);
 
 	nvme_mpath_remove_disk(head);
+	nvme_mpath_put_disk(head);
 	ida_simple_remove(&head->subsys->ns_ida, head->instance);
 	cleanup_srcu_struct(&head->srcu);
 	nvme_put_subsystem(head->subsys);
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index d5773ea105b1..f995b8234622 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -724,6 +724,8 @@ void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id)
 
 void nvme_mpath_remove_disk(struct nvme_ns_head *head)
 {
+	if (test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags))
+		return;
 	if (!head->disk)
 		return;
 	if (head->disk->flags & GENHD_FL_UP)
@@ -741,7 +743,6 @@ void nvme_mpath_remove_disk(struct nvme_ns_head *head)
 		 */
 		head->disk->queue = NULL;
 	}
-	put_disk(head->disk);
 }
 
 int nvme_mpath_init(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id)
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 3d2513f8194d..e6efa085f08a 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -681,8 +681,12 @@ static inline void nvme_mpath_check_last_path(struct nvme_ns *ns)
 {
 	struct nvme_ns_head *head = ns->head;
 
-	if (head->disk && list_empty(&head->list))
-		kblockd_schedule_work(&head->requeue_work);
+	if (head->disk && list_empty(&head->list)) {
+		if (test_bit(NVME_NSHEAD_FAIL_IF_NO_PATH, &head->flags))
+			nvme_mpath_remove_disk(head);
+		else
+			kblockd_schedule_work(&head->requeue_work);
+	}
 }
 
 static inline void nvme_trace_bio_complete(struct request *req)
@@ -693,6 +697,12 @@ static inline void nvme_trace_bio_complete(struct request *req)
 		trace_block_bio_complete(ns->head->disk->queue, req->bio);
 }
 
+static inline void nvme_mpath_put_disk(struct nvme_ns_head *head)
+{
+	if (head->disk)
+		put_disk(head->disk);
+}
+
 extern struct device_attribute dev_attr_ana_grpid;
 extern struct device_attribute dev_attr_ana_state;
 extern struct device_attribute dev_attr_fail_if_no_path;
@@ -731,6 +741,9 @@ static inline void nvme_mpath_add_disk(struct nvme_ns *ns,
 static inline void nvme_mpath_remove_disk(struct nvme_ns_head *head)
 {
 }
+static inline void nvme_mpath_put_disk(struct nvme_ns_head *head)
+{
+}
 static inline bool nvme_mpath_clear_current_path(struct nvme_ns *ns)
 {
 	return false;
-- 
2.29.2