Re: [PATCH v2 1/2] srcu: Add list_splice_init_srcu()

[Qiliang Yuan]

On Wed, Nov 04, 2026 at 09:14:12AM -0800, Paul E. McKenney wrote:
> I am not inalterably opposed to adding a list_splice_init_srcu(),
> especially if quite a few more users show up, but here is what I was
> expecting people to do:
>
> 	static void synchronize_my_srcu(void)
> 	{
> 		synchronize_srcu(&my_srcu);
> 	}
>
> 	...
>
> 	list_splice_init_rcu(l, h, synchronize_my_srcu);
>
> We need at least six uses of the above idiom to break even on the line
> of code required for introducing a list_splice_init_srcu().

Christoph, as Paul would rather not add a helper for a single user, and
the idiom above doesn't fit nvme's per-controller srcu_struct, would you
be fine with taking v1, which open-codes the splice in
nvme_remove_namespaces()?

  https://lore.kernel.org/r/20261103-bug-nvme-remove-ns-srcu-v1-1-e239087d63ac@xxxxxxxxx

It fixes a crash and is meant for stable: a reader in nvme_wait_freeze()
can walk onto the on-stack list head and use stack memory as a struct
nvme_ns, which KASAN reports as a stack-out-of-bounds read, followed by
a page fault. A shared helper can follow if more SRCU users of
list_splice_init_rcu() show up.

Thanks,
Qiliang