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Wed, 19 Apr 2023 13:15:51 -0700 (PDT) Received: from [192.168.1.136] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id b5-20020a170902bd4500b001a19cf1b37esm11831037plx.40.2023.04.19.13.15.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Apr 2023 13:15:51 -0700 (PDT) Message-ID: <567b593e-2ad0-9bec-4e6f-4bbb3301524c@kernel.dk> Date: Wed, 19 Apr 2023 14:15:49 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v4 4/6] io_uring: rsrc: avoid use of vmas parameter in pin_user_pages() Content-Language: en-US To: Jason Gunthorpe , Matthew Wilcox Cc: Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , David Hildenbrand , Pavel Begunkov , io-uring@vger.kernel.org References: <956f4fc2204f23e4c00e9602ded80cb4e7b5df9b.1681831798.git.lstoakes@gmail.com> <936e8f52-00be-6721-cb3e-42338f2ecc2f@kernel.dk> <69f48cc6-8fc6-0c49-5a79-6c7d248e4ad5@kernel.dk> <8af483d2-0d3d-5ece-fb1d-a3654411752b@kernel.dk> From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: DE1A018000B X-Stat-Signature: odk54wpj9teap1hkjfhguuugkbxa3gdd X-HE-Tag: 1681935352-898189 X-HE-Meta: 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 mm6qm+qr 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/19/23 12:24?PM, Jason Gunthorpe wrote: > On Wed, Apr 19, 2023 at 07:23:00PM +0100, Matthew Wilcox wrote: >> On Wed, Apr 19, 2023 at 07:18:26PM +0100, Lorenzo Stoakes wrote: >>> So even if I did the FOLL_ALLOW_BROKEN_FILE_MAPPING patch series first, I >>> would still need to come along and delete a bunch of your code >>> afterwards. And unfortunately Pavel's recent change which insists on not >>> having different vm_file's across VMAs for the buffer would have to be >>> reverted so I expect it might not be entirely without discussion. >> >> I don't even understand why Pavel wanted to make this change. The >> commit log really doesn't say. >> >> commit edd478269640 >> Author: Pavel Begunkov >> Date: Wed Feb 22 14:36:48 2023 +0000 >> >> io_uring/rsrc: disallow multi-source reg buffers >> >> If two or more mappings go back to back to each other they can be passed >> into io_uring to be registered as a single registered buffer. That would >> even work if mappings came from different sources, e.g. it's possible to >> mix in this way anon pages and pages from shmem or hugetlb. That is not >> a problem but it'd rather be less prone if we forbid such mixing. >> >> Cc: >> Signed-off-by: Pavel Begunkov >> Signed-off-by: Jens Axboe >> >> It even says "That is not a problem"! So why was this patch merged >> if it's not fixing a problem? >> >> It's now standing in the way of an actual cleanup. So why don't we >> revert it? There must be more to it than this ... > > https://lore.kernel.org/all/61ded378-51a8-1dcb-b631-fda1903248a9@gmail.com/ Let's just kill that patch that, I can add a revert for 6.4. I had forgotten about that patch and guess I didn't realize that most of the issue do in fact just stem from that. -- Jens Axboe