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Message-ID: <Y7RhQ427Qbie/NRE@x1n>
Date: Tue, 3 Jan 2023 12:09:23 -0500
From: Peter Xu <peterx@...hat.com>
To: James Houghton <jthoughton@...gle.com>
Cc: Mike Kravetz <mike.kravetz@...cle.com>,
Muchun Song <songmuchun@...edance.com>,
David Hildenbrand <david@...hat.com>,
David Rientjes <rientjes@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Mina Almasry <almasrymina@...gle.com>,
Zach O'Keefe <zokeefe@...gle.com>,
Manish Mishra <manish.mishra@...anix.com>,
Naoya Horiguchi <naoya.horiguchi@....com>,
"Dr . David Alan Gilbert" <dgilbert@...hat.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Vlastimil Babka <vbabka@...e.cz>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Yang Shi <shy828301@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 34/47] hugetlb: userfaultfd: add support for
high-granularity UFFDIO_CONTINUE
On Tue, Dec 27, 2022 at 11:38:31AM -0500, James Houghton wrote:
> On Fri, Dec 23, 2022 at 1:38 PM Peter Xu <peterx@...hat.com> wrote:
> >
> > James,
> >
> > On Fri, Oct 21, 2022 at 04:36:50PM +0000, James Houghton wrote:
> > > + bool use_hgm = uffd_ctx_has_hgm(&dst_vma->vm_userfaultfd_ctx) &&
> > > + mode == MCOPY_ATOMIC_CONTINUE;
> >
> > Do you think in your new version use_hgm can work even for MISSING by
> > default?
>
> I don't think so -- UFFDIO_COPY will allocate a hugepage, so I'm not
> sure if it makes sense to allow it at high-granularity. If UFFDIO_COPY
> didn't allocate a new page, then it could make sense (maybe we'd need
> a new ioctl or new UFFDIO_COPY mode?). I think it makes most sense to
> add this with another series.
I forgot again on how the page cache is managed for the split pages,
sorry.. Yeah let's stick with minor mode for now.
--
Peter Xu
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