From: Lorenzo Stoakes <lstoakes@gmail.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Christoph Hellwig <hch@infradead.org>,
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>,
linux-fsdevel@vger.kernel.org, linux-perf-users@vger.kernel.org,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH v2] mm/gup: disallow GUP writing to file-backed mappings by default
Date: Tue, 25 Apr 2023 00:26:25 +0100 [thread overview]
Message-ID: <ff1bb8cd-896f-4c7f-a182-42112f5ac5af@lucifer.local> (raw)
In-Reply-To: <ZEcN92iJoe+3ANVc@nvidia.com>
On Mon, Apr 24, 2023 at 08:17:11PM -0300, Jason Gunthorpe wrote:
> On Tue, Apr 25, 2023 at 12:03:34AM +0100, Lorenzo Stoakes wrote:
>
> > Except you dirty a page that is mapped elsewhere that thought everything
> > was cleaned and... not sure the PTLs really help you much?
>
> If we have a writable PTE then while the PTE's PTL is held it is impossible
> for a FS to make the page clean as any cleaning action has to also
> take the PTL to make the PTE non-present or non-writable.
>
That's a very good point! Passing things back with a spinlock held feels
pretty icky though, and obviously a no-go for a FOLL_PIN. Perhaps for a
FOLL_GET this would be workable.
> > If we want to be more adventerous the opt-in variant could default to on
> > for FOLL_LONGTERM too, but that discussion can be had over on that patch
> > series.
>
> I think you should at least do this too to explain why io_uring code
> is moving into common code..
>
OK, I'll respin this as a v3 of this series then since we'll be defaulting
FOLL_LONGTERM at least (for which there seems to be broad consensus), but
also permit this flag to be set manually and set it for io_uring.
> Jason
next prev parent reply other threads:[~2023-04-24 23:26 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-24 7:43 Lorenzo Stoakes
2023-04-24 9:43 ` Christoph Hellwig
2023-04-24 10:17 ` Lorenzo Stoakes
2023-04-24 12:28 ` Jason Gunthorpe
2023-04-24 12:38 ` Christoph Hellwig
2023-04-24 13:26 ` Jason Gunthorpe
2023-04-24 12:38 ` Lorenzo Stoakes
2023-04-24 13:39 ` Jason Gunthorpe
2023-04-24 14:29 ` Lorenzo Stoakes
2023-04-24 17:36 ` Jason Gunthorpe
2023-04-24 18:22 ` Lorenzo Stoakes
2023-04-24 18:54 ` Jason Gunthorpe
2023-04-24 19:18 ` Lorenzo Stoakes
2023-04-24 22:53 ` Jason Gunthorpe
2023-04-24 23:03 ` Lorenzo Stoakes
2023-04-24 23:17 ` Jason Gunthorpe
2023-04-24 23:26 ` Lorenzo Stoakes [this message]
2023-04-24 23:30 ` Jason Gunthorpe
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