[PATCH 3/3] nvme-multipath: skip inaccessible paths during partition scan

[Hannes Reinecke]

When a path is switched to 'inaccessible' during partition scan
triggered via device_add_disk() and we only have one path the
system will be stuck as nvme_available_path() will always return
'true'. So I/O will never be completed and the system is stuck
in device_add_disk().
This patch introduces a flag NVME_NSHEAD_DISABLE_QUEUEING to
cause nvme_available_path() to always return NULL, and with
that I/O to be failed if all paths are unavailable.

Signed-off-by: Hannes Reinecke <hare at kernel.org>
---
 drivers/nvme/host/multipath.c | 10 +++++++++-
 drivers/nvme/host/nvme.h      |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index f72c5a6a2d8e..bcd70755c663 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -421,7 +421,8 @@ static bool nvme_available_path(struct nvme_ns_head *head)
 {
 	struct nvme_ns *ns;
 
-	if (!test_bit(NVME_NSHEAD_DISK_LIVE, &head->flags))
+	if (!test_bit(NVME_NSHEAD_DISK_LIVE, &head->flags) ||
+	    test_bit(NVME_NSHEAD_DISABLE_QUEUEING, &head->flags))
 		return NULL;
 
 	list_for_each_entry_rcu(ns, &head->list, siblings) {
@@ -646,8 +647,15 @@ static void nvme_mpath_set_live(struct nvme_ns *ns)
 	 * head.
 	 */
 	if (!test_and_set_bit(NVME_NSHEAD_DISK_LIVE, &head->flags)) {
+		/*
+		 * Disable queueing to ensure I/O is not retried on unusable
+		 * paths, which would cause the system to be stuck during
+		 * partition scan.
+		 */
+		set_bit(NVME_NSHEAD_DISABLE_QUEUEING, &head->flags);
 		rc = device_add_disk(&head->subsys->dev, head->disk,
 				     nvme_ns_attr_groups);
+		clear_bit(NVME_NSHEAD_DISABLE_QUEUEING, &head->flags);
 		if (rc) {
 			clear_bit(NVME_NSHEAD_DISK_LIVE, &head->flags);
 			return;
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 50515ad0f9d6..f45ca7c45fd2 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -493,6 +493,7 @@ struct nvme_ns_head {
 	struct mutex		lock;
 	unsigned long		flags;
 #define NVME_NSHEAD_DISK_LIVE	0
+#define NVME_NSHEAD_DISABLE_QUEUEING	1
 	struct nvme_ns __rcu	*current_path[];
 #endif
 };
-- 
2.35.3