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[34.79.100.158]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3912c0e2f4fsm20260383f8f.77.2025.03.12.01.34.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Mar 2025 01:34:30 -0700 (PDT) Date: Wed, 12 Mar 2025 08:34:25 +0000 From: Brendan Jackman To: David Hildenbrand Cc: Lorenzo Stoakes , Andrew Morton , Shuah Khan , Dev Jain , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 08/10] selftests/mm: Skip gup_longerm tests on weird filesystems Message-ID: References: <20250228-mm-selftests-v3-0-958e3b6f0203@google.com> <20250228-mm-selftests-v3-8-958e3b6f0203@google.com> <08023d47-dcf4-4efb-bf13-5aef3c6dca14@redhat.com> <16023193-6cb4-46d1-91c4-43342e7e6d30@redhat.com> <41923b80-55f4-44b6-bc59-60327e5308f4@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <41923b80-55f4-44b6-bc59-60327e5308f4@redhat.com> X-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: fjmcdymaw4x997pq615ttgnc7eyqrmwe X-Rspamd-Queue-Id: 5219F100002 X-HE-Tag: 1741768472-522531 X-HE-Meta: U2FsdGVkX1+7golxA7fVJfPf9BRLpfqJbX5THMPyU7/sG+v30gTGjlGFmt3DzjOND7np0e5Jz1fgOClKuocYUvn1/klgazzojaS2wQc/uX+SOBcWYw86upBg8homhWaYnoj++upSupFQ6KpV6qBMt77sXN7NOU4kO25xo0zJKmhRG+497e+68losSzV78IXRVxxMFfRffczJR8AKZvur/jB6vl0jO6tGR6hpqT1wKW4Dz90VrpvuXAnyqXZUFmq10eI+Z3fvWtK4Y5W46iKO0HJPr+hqpKJjXM7s/gUPmXJK1lkFez3A4hv/YhcRN4jyVIewv4SEqhgyJMj9nndrauzHJQOcvrGdt+8NxDwiLTF+ezSNqejbaGSdCGFOEBhx2ZPc3FZAiBppFxurRHyzonMPDuIFM1ik82PQvtLHUslMk8t2rN+Qj45EvJXfOK3olZvmkp+sZYH+JSzw+Dvf2N975UAeGGCUTSxoRy91rzUncvnu2S3xoU2MP1dQiE/fV9Yp1P/SpVUbuwJsshXgSe8hJzT5vTZKuxiAfU+pNM0HdGdLoawfOlFboD6Zd4xUIRhEKl31Wx6XgZbR8DnXV9PkyGRWRodIWJKo3arPfNXhlOJDSeS3zLrxTlRdkPf5ihKWDNEY2t8jRXIEw3efGmd8pEx7uKjATeqhAfz2Mp7R/2uUQuEjhT0wVR1UZuJEeVqMoEFYHtIS10IzOXdaAuYB9rGeCP3TEzyXbx3N6GA5Jle2XtRYzpC38wD9TtX+SFJZP1HohVQRCfsrd+OgGdyhHfoNJMF1Yb6KXTp7T8oMEI/wts8jFNK9jScyXt4incKoPn4z5teHVzs8mvklBFFJDxTTp5jwzl57kmPRjMjntAaoLcwiJHqhnmShZ5Cs8vVPIZ3N/iL8H9cwHDUDZbDthD+0zIFzQ526priXoVIwcwRmkO2TD1iy3gETLJ+GaGesCWlX/6xAicKbLCI PR8P0+5g 7anITXQqRsRvpa6B1KbtQG4A0Vv66vNMYf4hjXbdne+xpb0YZ3INJ/BDVGkQ+zxb7QUd5klKjADMF+zbBPAb+FXhTaTULuI4mQX3psMOHOnGwyvAW+zueMmM2hoY2h5BQaVHJIMMAsU0/3sJaTaO/xOUiqgKEmJhW2crwi+MDFz+67X4t8A9p0Is8VcCog39HiJDq+tp8VYnm7qjaDJVw9qfZaiAPjg0H75raeZZE5bncGzQckA2JoR0eVZ3B+YYr/LLBlg/e0KpTNVBQIRE26oRNS/BOYhA7iprm8rjFLrCMgQ10KtzF6dD14qJMo2rfr4+2RoEdtWtlkhUl25E4oHaStvIT/l4eBG3QXYUHgh85NoNPX8B6vZKaYzthHGQCr1hjCOO7g0jSqVFtyCtHpVAtUw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.094210, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Mar 11, 2025 at 08:53:02PM +0100, David Hildenbrand wrote: > > 2. 9pfs seems to pass the f_type through from the host. So you can't > > detect it this way anyway. > > > > [3. I guess overlayfs & friends would also be an issue here although > > that doesn't affect my usecase.] > > > > Anyway, I think we would have to scrape /proc/mounts to do this :( > > > > The question I am asking myself: is this a 9pfs design bug or is it a 9pfs > hypervisor bug. Because we shouldn't try too hard to work around hypervisor > bugs. > > Which 9pfs implementation are you using in the hypervisor? I'm using QEMU via virtme-ng. IIUC virtme-ng knows how to use viortfs for the rootfs, but for individually-mounted directories with --rwdir/--rodir it uses 9pfs unconditionally. Even if it's a bug in QEMU, I think it is worth working around this one way or another. QEMU by far the most practical way to run these tests, and virtme-ng is probably the most popular/practical way to do that. I think even if we are confident it's just a bunch of broken code that isn't even in Linux, it's pragmatic to spend a certain amount of energy on having green tests there. (Also, this f_type thing might be totally intentional specified filesystem behaviour, I don't know).