[PATCH] nvme: fix namespace removal list

[Nilay Shroff]

On 6/11/24 22:09, Christoph Hellwig wrote:
> On Tue, Jun 11, 2024 at 08:20:55AM -0700, Keith Busch wrote:
>>  	mutex_lock(&ctrl->namespaces_lock);
>>  	list_for_each_entry_safe(ns, next, &ctrl->namespaces, list) {
>> -		if (ns->head->ns_id > nsid)
>> -			list_splice_init_rcu(&ns->list, &rm_list,
>> -					     synchronize_rcu);
>> +		if (ns->head->ns_id > nsid) {
>> +			list_del_rcu(&ns->list);
>> +			list_add_tail_rcu(&ns->list, &rm_list);
>> +		}
> 
> Is this actually valid for a (S)RCU protected list?  If the entry gets
> added to the new list before the grace period has completed, we could
> trick a concurrent traversal into following the new list unless I'm
> mistaken (although chances I'm mistaken on RCU corner cases aren't that
> low..).
> 
> 
I think we need synchronize_srcu() before we add deleted ns to rm_list.

Thanks,
--Nilay