On Tue, Jun 11, 2024 at 10:40:13PM +0530, Nilay Shroff wrote:
>
>
> 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.
After we delete it, but yes.
There will also be a window during which the element is not in either
list, but given the name "rm_list", I am guessing that this is OK. ;-)
Thanx, Paul
