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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Tue, 12 Mar 2019 12:30:52 -0700
Message-ID: <CAPcyv4g-z8nkM1B65oR-3PT_RFQbmQMsM-J-P0-nzyvvJ8gVog@mail.gmail.com>
Subject: Re: [PATCH 09/10] mm/hmm: allow to mirror vma of a file on a DAX
 backed filesystem
To:     Jerome Glisse <jglisse@redhat.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ralph Campbell <rcampbell@nvidia.com>,
        John Hubbard <jhubbard@nvidia.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
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On Tue, Mar 12, 2019 at 12:06 PM Jerome Glisse <jglisse@redhat.com> wrote:
> On Tue, Mar 12, 2019 at 09:06:12AM -0700, Dan Williams wrote:
> > On Tue, Mar 12, 2019 at 8:26 AM Jerome Glisse <jglisse@redhat.com> wrote:
[..]
> > > Spirit of the rule is better than blind application of rule.
> >
> > Again, I fail to see why HMM is suddenly unable to make forward
> > progress when the infrastructure that came before it was merged with
> > consumers in the same development cycle.
> >
> > A gate to upstream merge is about the only lever a reviewer has to
> > push for change, and these requests to uncouple the consumer only
> > serve to weaken that review tool in my mind.
>
> Well let just agree to disagree and leave it at that and stop
> wasting each other time

I'm fine to continue this discussion if you are. Please be specific
about where we disagree and what aspect of the proposed rules about
merge staging are either acceptable, painful-but-doable, or
show-stoppers. Do you agree that HMM is doing something novel with
merge staging, am I off base there? I expect I can find folks that
would balk with even a one cycle deferment of consumers, but can we
start with that concession and see how it goes? I'm missing where I've
proposed something that is untenable for the future of HMM which is
addressing some real needs in gaps in the kernel's support for new
hardware.