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Message-ID: <40ed22bb-53e3-ddc2-45ca-f0e763f26242@redhat.com>
Date:   Tue, 16 May 2023 10:25:55 +0200
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Subject: Re: [PATCH v5 4/6] io_uring: rsrc: delegate VMA file-backed check to
 GUP
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To:     Jens Axboe <axboe@kernel.dk>, Lorenzo Stoakes <lstoakes@gmail.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Pavel Begunkov <asml.silence@gmail.com>,
        io-uring@vger.kernel.org, Jason Gunthorpe <jgg@ziepe.ca>,
        John Hubbard <jhubbard@nvidia.com>
References: <cover.1684097001.git.lstoakes@gmail.com>
 <642128d50f5423b3331e3108f8faf6b8ac0d957e.1684097002.git.lstoakes@gmail.com>
 <c44effe6-029e-4ccb-ce97-2ca5d5099c05@kernel.dk>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <c44effe6-029e-4ccb-ce97-2ca5d5099c05@kernel.dk>
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On 15.05.23 21:55, Jens Axboe wrote:
> On 5/14/23 3:26 PM, Lorenzo Stoakes wrote:
>> Now that the GUP explicitly checks FOLL_LONGTERM pin_user_pages() for
>> broken file-backed mappings in "mm/gup: disallow FOLL_LONGTERM GUP-nonfast
>> writing to file-backed mappings", there is no need to explicitly check VMAs
>> for this condition, so simply remove this logic from io_uring altogether.
> 
> Don't have the prerequisite patch handy (not in mainline yet), but if it
> just moves the check, then:
> 
> Reviewed-by: Jens Axboe <axboe@kernel.dk>
> 

Jens, please see my note regarding iouring:

https://lore.kernel.org/bpf/6e96358e-bcb5-cc36-18c3-ec5153867b9a@redhat.com/

With this patch, MAP_PRIVATE will work as expected (2), but there will 
be a change in return code handling (1) that we might have to document
in the man page.

-- 
Thanks,

David / dhildenb