From d567572906d986dedb78b37f111c44eba033f3ef Mon Sep 17 00:00:00 2001
From: Keith Busch <kbusch@kernel.org>
Date: Thu, 9 Apr 2020 09:08:59 -0700
Patch-mainline: v5.8-rc1
Git-commit: d567572906d986dedb78b37f111c44eba033f3ef
References: bsc#1181161
Subject: [PATCH] nvme: unlink head after removing last namespace

The driver had been unlinking the namespace head from the subsystem's
list only after the last reference was released, and outside of the
list's subsys->lock protection.

There is no reason to track an empty head, so unlink the entry from the
subsystem's list when the last namespace using that head is removed and
with the mutex lock protecting the list update. The next namespace to
attach reusing the previous NSID will allocate a new head rather than
find the old head with mismatched identifiers.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
---
 drivers/nvme/host/core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -395,7 +395,6 @@ static void nvme_free_ns_head(struct kre
 
 	nvme_mpath_remove_disk(head);
 	ida_simple_remove(&head->subsys->ns_ida, head->instance);
-	list_del_init(&head->entry);
 	cleanup_srcu_struct_quiesced(&head->srcu);
 	nvme_put_subsystem(head->subsys);
 	kfree(head);
@@ -2993,7 +2992,6 @@ static int __nvme_check_ids(struct nvme_
 
 	list_for_each_entry(h, &subsys->nsheads, entry) {
 		if (nvme_ns_ids_valid(&new->ids) &&
-		    !list_empty(&h->list) &&
 		    nvme_ns_ids_equal(&new->ids, &h->ids))
 			return -EINVAL;
 	}
@@ -3234,6 +3232,8 @@ static int nvme_alloc_ns(struct nvme_ctr
  out_unlink_ns:
 	mutex_lock(&ctrl->subsys->lock);
 	list_del_rcu(&ns->siblings);
+	if (list_empty(&ns->head->list))
+		list_del_init(&ns->head->entry);
 	mutex_unlock(&ctrl->subsys->lock);
  out_free_id:
 	kfree(id);
@@ -3255,7 +3255,10 @@ static void nvme_ns_remove(struct nvme_n
 
 	mutex_lock(&ns->ctrl->subsys->lock);
 	list_del_rcu(&ns->siblings);
+	if (list_empty(&ns->head->list))
+		list_del_init(&ns->head->entry);
 	mutex_unlock(&ns->ctrl->subsys->lock);
+
 	synchronize_rcu(); /* guarantee not available in head->list */
 	nvme_mpath_clear_current_path(ns);
 	synchronize_srcu(&ns->head->srcu); /* wait for concurrent submissions */