From: Mike Rapoport <rppt@kernel.org>
To: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>,
akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
selinux@vger.kernel.org, surenb@google.com,
kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com,
david@redhat.com, axelrasmussen@google.com, bgeffon@google.com,
willy@infradead.org, jannh@google.com, kaleshsingh@google.com,
ngeoffray@google.com, timmurray@google.com
Subject: Re: [PATCH v2 2/3] userfaultfd: protect mmap_changing with rw_sem in userfaulfd_ctx
Date: Mon, 12 Feb 2024 10:14:30 +0200 [thread overview]
Message-ID: <ZcnTZiyHRf4Dj3P2@kernel.org> (raw)
In-Reply-To: <CA+EESO6V9HiPtFpG7-cjvadj_BcKzGvi4GSdJBXD_zTM+EQu5A@mail.gmail.com>
On Wed, Feb 07, 2024 at 12:24:52PM -0800, Lokesh Gidra wrote:
> On Wed, Feb 7, 2024 at 7:27 AM Mike Rapoport <rppt@kernel.org> wrote:
> >
> > > > The write-lock is not a requirement here for correctness and I don't see
> > > > why we would need userfaultfd_remove_prep().
> > > >
> > > > As I've said earlier, having a write-lock here will let CRIU to run
> > > > background copy in parallel with processing of uffd events, but I don't
> > > > feel strongly about doing it.
> > > >
> > > Got it. Anyways, such a change needn't be part of this patch, so I'm
> > > going to keep it unchanged.
> >
> > You mean with a read lock?
>
> No, I think write lock is good as it enables parallel background copy.
> Also because it brings consistency in blocking userfaultfd operations.
>
> I meant encapsulating remove operations within
> userfaultfd_remove_prep() and userfaultfd_remove_complete(). I
> couldn't figure out any need for that.
I don't think there is a need for that. With fork/mremap prep is required
to ensure there's uffd context for new vmas.
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2024-02-12 8:14 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-29 19:35 [PATCH v2 0/3] per-vma locks in userfaultfd Lokesh Gidra
2024-01-29 19:35 ` [PATCH v2 1/3] userfaultfd: move userfaultfd_ctx struct to header file Lokesh Gidra
2024-01-30 7:12 ` Mike Rapoport
2024-01-29 19:35 ` [PATCH v2 2/3] userfaultfd: protect mmap_changing with rw_sem in userfaulfd_ctx Lokesh Gidra
2024-01-29 21:00 ` Liam R. Howlett
2024-01-29 22:35 ` Lokesh Gidra
2024-01-30 3:46 ` Liam R. Howlett
2024-01-30 8:55 ` Mike Rapoport
2024-01-30 17:28 ` Liam R. Howlett
2024-01-31 2:24 ` Lokesh Gidra
2024-02-04 10:27 ` Mike Rapoport
2024-02-05 20:53 ` Lokesh Gidra
2024-02-07 15:27 ` Mike Rapoport
2024-02-07 20:24 ` Lokesh Gidra
2024-02-12 8:14 ` Mike Rapoport [this message]
2024-01-30 7:21 ` Mike Rapoport
2024-01-29 19:35 ` [PATCH v2 3/3] userfaultfd: use per-vma locks in userfaultfd operations Lokesh Gidra
2024-01-29 20:36 ` Liam R. Howlett
2024-01-29 20:52 ` Suren Baghdasaryan
2024-01-29 21:18 ` Liam R. Howlett
2024-01-30 0:28 ` Lokesh Gidra
2024-01-30 2:58 ` Liam R. Howlett
2024-01-31 2:49 ` Lokesh Gidra
2024-01-31 21:41 ` Liam R. Howlett
2024-02-05 21:46 ` Suren Baghdasaryan
2024-02-05 21:54 ` Lokesh Gidra
2024-02-05 22:00 ` Liam R. Howlett
2024-02-05 22:24 ` Lokesh Gidra
2024-02-06 14:35 ` Liam R. Howlett
2024-02-06 16:26 ` Lokesh Gidra
2024-02-06 17:07 ` Liam R. Howlett
2024-01-31 3:03 ` Suren Baghdasaryan
2024-01-31 21:43 ` Liam R. Howlett
2024-01-29 20:39 ` [PATCH v2 0/3] per-vma locks in userfaultfd Liam R. Howlett
2024-01-29 21:58 ` Lokesh Gidra
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