[PATCH] nvme: fix (S)RCU protection of nvme_ns_head list (alternate)

[Christoph Hellwig]

On Wed, Nov 23, 2022 at 05:24:32PM -0700, Caleb Sander wrote:
> +++ b/drivers/nvme/host/multipath.c
> @@ -175,10 +175,12 @@ void nvme_mpath_revalidate_paths(struct nvme_ns *ns)
>  	sector_t capacity = get_capacity(head->disk);
>  	int node;
>  
> +	rcu_read_lock();
>  	list_for_each_entry_rcu(ns, &head->list, siblings) {
>  		if (capacity != get_capacity(ns->disk))
>  			clear_bit(NVME_NS_READY, &ns->flags);
>  	}
> +	rcu_read_unlock();

I can't see how protection iteraction of the same list once with
SRCU and once with RCU can work in practice.