nvme: unlink head after removing last namespace

mainline inclusion
from mainline-v5.8-rc1
commit d5675729
category: bugfix
bugzilla: NA
CVE: NA
Link: https://gitee.com/openeuler/kernel/issues/I1WGZE

--------------------------------

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: NKeith Busch <kbusch@kernel.org>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Reviewed-by: NChao Leng <lengchao@huawei.com>
Reviewed-by: NJike Cheng <chengjike.cheng@huawei.com>
Signed-off-by: NLijie <lijie34@huawei.com>
Acked-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/nvme/host/core.c

@@ -397,7 +397,6 @@ static void nvme_free_ns_head(struct kref *ref)
 
 	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);
@@ -3065,7 +3064,6 @@ static int __nvme_check_ids(struct nvme_subsystem *subsys,
 
 	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;
 	}
@@ -3293,6 +3291,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
  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);
 	nvme_put_ns_head(ns->head);
  out_free_id:
@@ -3312,7 +3312,10 @@ static void nvme_ns_remove(struct nvme_ns *ns)
 
 	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 */