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[81.154.179.160]) by smtp.gmail.com with ESMTPSA id v7-20020a05600c214700b003f4f89bc48dsm15111555wml.15.2023.05.28.08.13.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 28 May 2023 08:13:45 -0700 (PDT) Date: Sun, 28 May 2023 16:13:44 +0100 From: Lorenzo Stoakes To: Jason Gunthorpe Cc: Arnd Bergmann , Andrew Morton , Arnd Bergmann , Catalin Marinas , Will Deacon , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org Subject: Re: [PATCH] [suggestion] mm/gup: avoid IS_ERR_OR_NULL Message-ID: <617c2e26-8450-4a35-9b47-c0482921f030@lucifer.local> References: <20230519093953.10972-1-arnd@kernel.org> <5b071f65-7f87-4a7b-a76a-f4a1c1568ae7@lucifer.local> <1ca47b8a-292c-47ab-aa6f-ca24fdfc0d3c@lucifer.local> <0bc9dc2b-0da6-4d5c-96af-e21aa287eecb@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 996BA140008 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: tzgnsjfh1wze683oqkju3cjtkf7pzmwi X-HE-Tag: 1685286828-417066 X-HE-Meta: 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 4gXrQnCY 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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 Sat, May 27, 2023 at 06:52:01AM -0300, Jason Gunthorpe wrote: > On Sat, May 20, 2023 at 10:12:40AM +0100, Lorenzo Stoakes wrote: > > > No, this returning 0 on failure is a foot gun. Failing to pin a single > > > page is always an error, the only question is what sub reason caused > > > the error to happen. There is no third case where it is not an error. > > > > The uprobe path thinks otherwise, but maybe the answer is that we just need > > to -EFAULT on missing VMA and -EPERM on invalid flags. > > I think uprobe is just broken to think there is a third outcome. Let's > just fix it instead of trying to pretend it makes sense. Sure, will take a look at that if I get a chance. We can at the very least adjust get_user_page_vma_remote() with this fixed. Do you feel that a partially successful pinning for other GUP callers should equally be treated as an error (and pages unpinned -> return error code)? In that instance we'd need to audit things somewhat. I have a couple more GUP cleanups saved up, so could add that to my queue of things to look at between book work :) > > Jason > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel