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Message-ID: <ZEcN92iJoe+3ANVc@nvidia.com>
Date: Mon, 24 Apr 2023 20:17:11 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Lorenzo Stoakes <lstoakes@...il.com>
Cc: Christoph Hellwig <hch@...radead.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
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Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH v2] mm/gup: disallow GUP writing to file-backed mappings
by default
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.
> 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..
Jason
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