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From: Andrew Morton <akpm@linux-foundation.org>
To: Jerome Glisse <jglisse@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
	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>
Subject: Re: [PATCH 09/10] mm/hmm: allow to mirror vma of a file on a DAX backed filesystem
Date: Wed, 13 Mar 2019 09:06:04 -0700	[thread overview]
Message-ID: <20190313090604.968100351b19338cacbfa3bc@linux-foundation.org> (raw)
In-Reply-To: <20190313001018.GA3312@redhat.com>

On Tue, 12 Mar 2019 20:10:19 -0400 Jerome Glisse <jglisse@redhat.com> wrote:

> > You're correct.  We chose to go this way because the HMM code is so
> > large and all-over-the-place that developing it in a standalone tree
> > seemed impractical - better to feed it into mainline piecewise.
> > 
> > This decision very much assumed that HMM users would definitely be
> > merged, and that it would happen soon.  I was skeptical for a long time
> > and was eventually persuaded by quite a few conversations with various
> > architecture and driver maintainers indicating that these HMM users
> > would be forthcoming.
> > 
> > In retrospect, the arrival of HMM clients took quite a lot longer than
> > was anticipated and I'm not sure that all of the anticipated usage
> > sites will actually be using it.  I wish I'd kept records of
> > who-said-what, but I didn't and the info is now all rather dissipated.
> > 
> > So the plan didn't really work out as hoped.  Lesson learned, I would
> > now very much prefer that new HMM feature work's changelogs include
> > links to the driver patchsets which will be using those features and
> > acks and review input from the developers of those driver patchsets.
> 
> This is what i am doing now and this patchset falls into that. I did
> post the ODP and nouveau bits to use the 2 new functions (dma map and
> unmap). I expect to merge both ODP and nouveau bits for that during
> the next merge window.
> 
> Also with 5.1 everything that is upstream is use by nouveau at least.
> They are posted patches to use HMM for AMD, Intel, Radeon, ODP, PPC.
> Some are going through several revisions so i do not know exactly when
> each will make it upstream but i keep working on all this.
> 
> So the guideline we agree on:
>     - no new infrastructure without user
>     - device driver maintainer for which new infrastructure is done
>       must either sign off or review of explicitly say that they want
>       the feature I do not expect all driver maintainer will have
>       the bandwidth to do proper review of the mm part of the infra-
>       structure and it would not be fair to ask that from them. They
>       can still provide feedback on the API expose to the device
>       driver.

The patchset in -mm ("HMM updates for 5.1") has review from Ralph
Campbell @ nvidia.  Are there any other maintainers who we should have
feedback from?

>     - driver bits must be posted at the same time as the new infra-
>       structure even if they target the next release cycle to avoid
>       inter-tree dependency
>     - driver bits must be merge as soon as possible

Are there links to driver patchsets which we can add to the changelogs?

> Thing we do not agree on:
>     - If driver bits miss for any reason the +1 target directly
>       revert the new infra-structure. I think it should not be black
>       and white and the reasons why the driver bit missed the merge
>       window should be taken into account. If the feature is still
>       wanted and the driver bits missed the window for simple reasons
>       then it means that we push everything by 2 release ie the
>       revert is done in +1 then we reupload the infra-structure in
>       +2 and finaly repush the driver bit in +3 so we loose 1 cycle.
>       Hence why i would rather that the revert would only happen if
>       it is clear that the infrastructure is not ready or can not
>       be use in timely (over couple kernel release) fashion by any
>       drivers.

I agree that this should be more a philosophy than a set of hard rules.


  parent reply	other threads:[~2019-03-13 16:06 UTC|newest]

Thread overview: 98+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-29 16:54 [PATCH 00/10] HMM updates for 5.1 jglisse
2019-01-29 16:54 ` [PATCH 01/10] mm/hmm: use reference counting for HMM struct jglisse
2019-02-20 23:47   ` John Hubbard
2019-02-20 23:59     ` Jerome Glisse
2019-02-21  0:06       ` John Hubbard
2019-02-21  0:15         ` Jerome Glisse
2019-02-21  0:32           ` John Hubbard
2019-02-21  0:37             ` Jerome Glisse
2019-02-21  0:42               ` John Hubbard
2019-01-29 16:54 ` [PATCH 02/10] mm/hmm: do not erase snapshot when a range is invalidated jglisse
2019-02-20 23:58   ` John Hubbard
2019-01-29 16:54 ` [PATCH 03/10] mm/hmm: improve and rename hmm_vma_get_pfns() to hmm_range_snapshot() jglisse
2019-02-21  0:25   ` John Hubbard
2019-02-21  0:28     ` Jerome Glisse
2019-01-29 16:54 ` [PATCH 04/10] mm/hmm: improve and rename hmm_vma_fault() to hmm_range_fault() jglisse
2019-01-29 16:54 ` [PATCH 05/10] mm/hmm: improve driver API to work and wait over a range jglisse
2019-01-29 16:54 ` [PATCH 06/10] mm/hmm: add default fault flags to avoid the need to pre-fill pfns arrays jglisse
2019-01-29 16:54 ` [PATCH 07/10] mm/hmm: add an helper function that fault pages and map them to a device jglisse
2019-03-18 20:21   ` Dan Williams
2019-03-18 20:41     ` Jerome Glisse
2019-03-18 21:30       ` Dan Williams
2019-03-18 22:15         ` Jerome Glisse
2019-03-19  3:29           ` Dan Williams
2019-03-19 13:30             ` Jerome Glisse
2019-03-19  8:44               ` Ira Weiny
2019-03-19 17:10                 ` Jerome Glisse
2019-03-19 14:10                   ` Ira Weiny
2019-01-29 16:54 ` [PATCH 08/10] mm/hmm: support hugetlbfs (snap shoting, faulting and DMA mapping) jglisse
2019-01-29 16:54 ` [PATCH 09/10] mm/hmm: allow to mirror vma of a file on a DAX backed filesystem jglisse
2019-01-29 18:41   ` Dan Williams
2019-01-29 19:31     ` Jerome Glisse
2019-01-29 20:51       ` Dan Williams
2019-01-29 21:21         ` Jerome Glisse
2019-01-30  2:32           ` Dan Williams
2019-01-30  3:03             ` Jerome Glisse
2019-01-30 17:25               ` Dan Williams
2019-01-30 18:36                 ` Jerome Glisse
2019-01-31  3:28                   ` Dan Williams
2019-01-31  4:16                     ` Jerome Glisse
2019-01-31  5:44                       ` Dan Williams
2019-03-05 22:16                         ` Andrew Morton
2019-03-06  4:20                           ` Dan Williams
2019-03-06 15:51                             ` Jerome Glisse
2019-03-06 15:57                               ` Dan Williams
2019-03-06 16:03                                 ` Jerome Glisse
2019-03-06 16:06                                   ` Dan Williams
2019-03-07 17:46                             ` Andrew Morton
2019-03-07 18:56                               ` Jerome Glisse
2019-03-12  3:13                                 ` Dan Williams
2019-03-12 15:25                                   ` Jerome Glisse
2019-03-12 16:06                                     ` Dan Williams
2019-03-12 19:06                                       ` Jerome Glisse
2019-03-12 19:30                                         ` Dan Williams
2019-03-12 20:34                                           ` Dave Chinner
2019-03-13  1:06                                             ` Dan Williams
2019-03-12 21:52                                           ` Andrew Morton
2019-03-13  0:10                                             ` Jerome Glisse
2019-03-13  0:46                                               ` Dan Williams
2019-03-13  1:00                                                 ` Jerome Glisse
2019-03-13 16:06                                               ` Andrew Morton [this message]
2019-03-13 18:39                                                 ` Jerome Glisse
2019-03-06 15:49                           ` Jerome Glisse
2019-03-06 22:18                             ` Andrew Morton
2019-03-07  0:36                               ` Jerome Glisse
2019-01-29 16:54 ` [PATCH 10/10] mm/hmm: add helpers for driver to safely take the mmap_sem jglisse
2019-02-20 21:59   ` John Hubbard
2019-02-20 22:19     ` Jerome Glisse
2019-02-20 22:40       ` John Hubbard
2019-02-20 23:09         ` Jerome Glisse
2019-02-20 23:17 ` [PATCH 00/10] HMM updates for 5.1 John Hubbard
2019-02-20 23:36   ` Jerome Glisse
2019-02-22 23:31 ` Ralph Campbell
2019-03-13  1:27 ` Jerome Glisse
2019-03-13 16:10   ` Andrew Morton
2019-03-13 18:01     ` Jason Gunthorpe
2019-03-13 18:33     ` Jerome Glisse
2019-03-18 17:00     ` Kuehling, Felix
2019-03-18 17:04     ` Jerome Glisse
2019-03-18 18:30       ` Dan Williams
2019-03-18 18:54         ` Jerome Glisse
2019-03-18 19:18           ` Dan Williams
2019-03-18 19:28             ` Jerome Glisse
2019-03-18 19:36               ` Dan Williams
2019-03-19 16:40       ` Andrew Morton
2019-03-19 16:58         ` Jerome Glisse
2019-03-19 17:12           ` Andrew Morton
2019-03-19 17:18             ` Jerome Glisse
2019-03-19 17:33               ` Dan Williams
2019-03-19 17:45                 ` Jerome Glisse
2019-03-19 18:42                   ` Dan Williams
2019-03-19 19:05                     ` Jerome Glisse
2019-03-19 19:13                       ` Dan Williams
2019-03-19 14:18                         ` Ira Weiny
2019-03-19 22:24                           ` Jerome Glisse
2019-03-19 19:18                         ` Jerome Glisse
2019-03-19 20:25                           ` Jerome Glisse
2019-03-19 21:51             ` Stephen Rothwell
2019-03-19 18:51           ` Deucher, Alexander

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