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([2620:10d:c092:600::2:7db2]) by smtp.gmail.com with ESMTPSA id k1-20020a170906a38100b0094ece70481csm721119ejz.197.2023.04.20.06.41.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Apr 2023 06:41:13 -0700 (PDT) Message-ID: <502f1114-6fd1-0bf8-fc22-08690cfe6cf5@gmail.com> Date: Thu, 20 Apr 2023 14:37:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v4 4/6] io_uring: rsrc: avoid use of vmas parameter in pin_user_pages() Content-Language: en-US To: Jens Axboe , Jason Gunthorpe , Matthew Wilcox Cc: Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , David Hildenbrand , 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> <567b593e-2ad0-9bec-4e6f-4bbb3301524c@kernel.dk> From: Pavel Begunkov In-Reply-To: <567b593e-2ad0-9bec-4e6f-4bbb3301524c@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 7E51140007 X-Stat-Signature: 7x61f7qokrp5m3nrbkp63jb7xna754j8 X-Rspam-User: X-HE-Tag: 1681998075-801536 X-HE-Meta: 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 1ceKGVVD 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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 21:15, Jens Axboe wrote: > 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. Well, we're now trading uapi sanity for cleanups, I don't know what I should take out of it. -- Pavel Begunkov