Re: [PATCH 07/12] s390: add pte_free_defer(), with use of mmdrop_async()

On Tue, 6 Jun 2023, Jason Gunthorpe wrote:

On Mon, Jun 05, 2023 at 10:11:52PM -0700, Hugh Dickins wrote:

quoted

"deposited" pagetable fragments, over in arch/s390/mm/pgtable.c: use
the first two longs of the page table itself for threading the list.

It is not RCU anymore if it writes to the page table itself before the
grace period, so this change seems to break the RCU behavior of
page_table_free_rcu().. The rcu sync is inside tlb_remove_table()
called after the stores.

Yes indeed, thanks for pointing that out.

Maybe something like an xarray on the mm to hold the frags?

I think we can manage without that:
I'll say slightly more in reply to Gerald.

Hugh