From: Jason Gunthorpe <jgg@nvidia.com>
To: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>,
Matthew Wilcox <willy@infradead.org>,
Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>,
Leon Romanovsky <leon@kernel.org>,
Christian Benvenuti <benve@cisco.com>,
Nelson Escobar <neescoba@cisco.com>,
Bernard Metzler <bmt@zurich.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Bjorn Topel <bjorn@kernel.org>,
Magnus Karlsson <magnus.karlsson@intel.com>,
Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
Jonathan Lemon <jonathan.lemon@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Christian Brauner <brauner@kernel.org>,
Richard Cochran <richardcochran@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
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netdev@vger.kernel.org, bpf@vger.kernel.org,
Oleg Nesterov <oleg@redhat.com>,
John Hubbard <jhubbard@nvidia.com>, Jan Kara <jack@suse.cz>,
Pavel Begunkov <asml.silence@gmail.com>,
Mika Penttila <mpenttil@redhat.com>,
David Hildenbrand <david@redhat.com>,
Dave Chinner <david@fromorbit.com>, Theodore Ts'o <tytso@mit.edu>,
Peter Xu <peterx@redhat.com>,
Matthew Rosato <mjrosato@linux.ibm.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Christian Borntraeger <borntraeger@linux.ibm.com>
Subject: Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed mappings by default
Date: Mon, 15 May 2023 09:12:49 -0300 [thread overview]
Message-ID: <ZGIhwZl2FbLodLrc@nvidia.com> (raw)
In-Reply-To: <7f6dbe36-88f2-468e-83c1-c97e666d8317@lucifer.local>
On Mon, May 15, 2023 at 12:16:21PM +0100, Lorenzo Stoakes wrote:
> > One thing that came to mind is KVM with "qemu -object memory-backend-file,share=on..."
> > It is mostly used for pmem emulation.
> >
> > Do we have plan B?
>
> Yes, we can make it opt-in or opt-out via a FOLL_FLAG. This would be easy
> to implement in the event of any issues arising.
I'm becoming less keen on the idea of a per-subsystem opt out. I think
we should make a kernel wide opt out. I like the idea of using lower
lockdown levels. Lots of things become unavaiable in the uAPI when the
lockdown level increases already.
> Jason will have some thoughts on this I'm sure. I guess the key question
> here is - is it actually feasible for this to work at all? Once we
> establish that, the rest are details :)
Surely it is, but like Ted said, the FS folks are not interested and
they are at least half the solution..
The FS also has to actively not write out the page while it cannot be
write protected unless it copies the data to a stable page. The block
stack needs the source data to be stable to do checksum/parity/etc
stuff. It is a complicated subject.
Jason
next prev parent reply other threads:[~2023-05-15 12:12 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-04 21:27 [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed mappings by default Lorenzo Stoakes
2023-05-04 21:27 ` [PATCH v9 1/3] mm/mmap: separate writenotify and dirty tracking logic Lorenzo Stoakes
2023-05-04 21:27 ` [PATCH v9 2/3] mm/gup: disallow FOLL_LONGTERM GUP-nonfast writing to file-backed mappings Lorenzo Stoakes
2023-05-04 21:27 ` [PATCH v9 3/3] mm/gup: disallow FOLL_LONGTERM GUP-fast " Lorenzo Stoakes
2023-05-05 20:21 ` [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed mappings by default David Hildenbrand
2023-05-05 21:12 ` Lorenzo Stoakes
2023-05-14 19:20 ` Lorenzo Stoakes
2023-05-15 5:14 ` Christoph Hellwig
2023-05-15 11:31 ` Lorenzo Stoakes
2023-05-17 8:26 ` David Hildenbrand
2023-05-15 11:03 ` Kirill A . Shutemov
2023-05-15 11:16 ` Lorenzo Stoakes
2023-05-15 12:12 ` Jason Gunthorpe [this message]
2023-05-15 13:07 ` Lorenzo Stoakes
2023-05-17 7:29 ` Jan Kara
2023-05-17 7:40 ` Lorenzo Stoakes
2023-05-17 7:43 ` Christoph Hellwig
2023-05-17 7:55 ` Lorenzo Stoakes
2023-05-17 8:10 ` Christoph Hellwig
2023-05-17 7:42 ` Christoph Hellwig
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