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Date:   Wed, 7 Jun 2023 19:46:26 -0700 (PDT)
From:   Hugh Dickins <hughd@google.com>
To:     Jason Gunthorpe <jgg@ziepe.ca>
cc:     Hugh Dickins <hughd@google.com>,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
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Subject: Re: [PATCH 07/12] s390: add pte_free_defer(), with use of
 mmdrop_async()
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On Tue, 6 Jun 2023, Jason Gunthorpe wrote:
> On Mon, Jun 05, 2023 at 10:11:52PM -0700, Hugh Dickins wrote:
> 
> > "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