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From: Peter Xu <peterx@redhat.com>
To: Axel Rasmussen <axelrasmussen@google.com>
Cc: Hugh Dickins <hughd@google.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jerome Glisse <jglisse@redhat.com>, Joe Perches <joe@perches.com>,
	Lokesh Gidra <lokeshgidra@google.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>, Shaohua Li <shli@fb.com>,
	Shuah Khan <shuah@kernel.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Wang Qing <wangqing@vivo.com>,
	linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	linux-kselftest@vger.kernel.org, Linux MM <linux-mm@kvack.org>,
	Brian Geffon <bgeffon@google.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	Mina Almasry <almasrymina@google.com>,
	Oliver Upton <oupton@google.com>
Subject: Re: [PATCH v4 03/10] userfaultfd/shmem: support UFFDIO_CONTINUE for shmem
Date: Tue, 27 Apr 2021 14:03:14 -0400	[thread overview]
Message-ID: <20210427180314.GD6820@xz-x1> (raw)
In-Reply-To: <CAJHvVciNrE_F0B0nu=Mib6LhcFhL8+qgO-yiKNsJuBjOMkn5+g@mail.gmail.com>

On Tue, Apr 27, 2021 at 09:57:16AM -0700, Axel Rasmussen wrote:
> I'd prefer to keep them separate, as they are not tiny patches (they
> are roughly +200/-150 each). And, they really are quite independent -
> at least in the sense that I can reorder them via rebase with no
> conflicts, and the code builds at each commit in either orientation. I
> think this implies they're easier to review separately, rather than
> squashed.
> 
> I don't have a strong feeling about the order. I slightly prefer
> swapping them compared to this v4 series: first introduce minor
> faults, then introduce CONTINUE.
> 
> Since Peter also has no strong opinion, and Hugh it sounds like you
> prefer it the other way around, I'll swap them as we had in some
> previous version of this series: first introduce minor faults, then
> introduce CONTINUE.

Yes I have no strong opinion, but that's probably the least I prefer. :-)

Because you'll declare UFFD_FEATURE_MINOR_SHMEM and enable this feature without
the feature being completely implemented (without UFFDIO_CONTINUE, it's not
complete since no one will be able to resolve that minor fault).

Not a big deal anyway, but since we're at it... Basically I think three things
to do for minor shmem support:

  (1) UFFDIO_CONTINUE (resolving path)
  (2) Handle fault path for shmem minor fault (faulting path)
  (3) Enablement of UFFD_FEATURE_MINOR_SHMEM (from which point, user can detect
      and enable it)

I have no preference on how you'd like to merge these steps (right now you did
1 first, then 2+3 later; or as Hugh suggested do 1+2+3 together), but I'd still
hope item 3 should always be the last, if possible...

Thanks,

-- 
Peter Xu


  reply	other threads:[~2021-04-27 18:03 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-20 22:07 [PATCH v4 00/10] userfaultfd: add minor fault handling for shmem Axel Rasmussen
2021-04-20 22:07 ` Axel Rasmussen
2021-04-20 22:07 ` [PATCH v4 01/10] userfaultfd/hugetlbfs: avoid including userfaultfd_k.h in hugetlb.h Axel Rasmussen
2021-04-20 22:07   ` Axel Rasmussen
2021-04-27  2:05   ` Hugh Dickins
2021-04-27  2:05     ` Hugh Dickins
2021-04-20 22:07 ` [PATCH v4 02/10] userfaultfd/shmem: combine shmem_{mcopy_atomic,mfill_zeropage}_pte Axel Rasmussen
2021-04-20 22:07   ` Axel Rasmussen
2021-04-20 22:07 ` [PATCH v4 03/10] userfaultfd/shmem: support UFFDIO_CONTINUE for shmem Axel Rasmussen
2021-04-20 22:07   ` Axel Rasmussen
2021-04-22 20:22   ` Axel Rasmussen
2021-04-22 20:22     ` Axel Rasmussen
2021-04-22 21:18     ` Peter Xu
2021-04-22 22:05       ` Axel Rasmussen
2021-04-22 22:05         ` Axel Rasmussen
2021-04-27  2:19   ` Hugh Dickins
2021-04-27  2:19     ` Hugh Dickins
2021-04-27 15:54     ` Peter Xu
2021-04-27 16:57       ` Axel Rasmussen
2021-04-27 16:57         ` Axel Rasmussen
2021-04-27 18:03         ` Peter Xu [this message]
2021-04-27 20:29           ` Axel Rasmussen
2021-04-27 20:29             ` Axel Rasmussen
2021-04-27 20:42             ` Peter Xu
2021-04-27 20:59               ` Hugh Dickins
2021-04-27 20:59                 ` Hugh Dickins
2021-04-20 22:07 ` [PATCH v4 04/10] userfaultfd/shmem: support minor fault registration " Axel Rasmussen
2021-04-20 22:07   ` Axel Rasmussen
2021-04-27  2:23   ` Hugh Dickins
2021-04-27  2:23     ` Hugh Dickins
2021-04-27 15:57     ` Peter Xu
2021-04-27 17:03       ` Axel Rasmussen
2021-04-27 17:03         ` Axel Rasmussen
2021-04-20 22:07 ` [PATCH v4 05/10] userfaultfd/selftests: use memfd_create for shmem test type Axel Rasmussen
2021-04-20 22:07   ` Axel Rasmussen
2021-04-20 22:08 ` [PATCH v4 06/10] userfaultfd/selftests: create alias mappings in the shmem test Axel Rasmussen
2021-04-20 22:08   ` Axel Rasmussen
2021-04-20 22:08 ` [PATCH v4 07/10] userfaultfd/selftests: reinitialize test context in each test Axel Rasmussen
2021-04-20 22:08   ` Axel Rasmussen
2021-04-20 22:08 ` [PATCH v4 08/10] userfaultfd/selftests: exercise minor fault handling shmem support Axel Rasmussen
2021-04-20 22:08   ` Axel Rasmussen
2021-04-20 22:08 ` [PATCH v4 09/10] userfaultfd/shmem: modify shmem_mcopy_atomic_pte to use install_pte() Axel Rasmussen
2021-04-20 22:08   ` Axel Rasmussen
2021-04-21  1:02   ` Peter Xu
2021-04-27  2:59     ` Hugh Dickins
2021-04-27  2:59       ` Hugh Dickins
2021-04-20 22:08 ` [PATCH v4 10/10] userfaultfd: update documentation to mention shmem minor faults Axel Rasmussen
2021-04-20 22:08   ` Axel Rasmussen
2021-04-27  2:27   ` Hugh Dickins
2021-04-27  2:27     ` Hugh Dickins

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