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Sat, 2 May 2020 15:10:29 -0400 (EDT) Received: from vostro.rath.org (vostro [192.168.12.4]) by ebox.rath.org (Postfix) with ESMTPS id 878BF23; Sat, 2 May 2020 19:10:28 +0000 (UTC) Received: by vostro.rath.org (Postfix, from userid 1000) id 4BE8CE29E2; Sat, 2 May 2020 20:09:23 +0100 (BST) From: Nikolaus Rath To: linux-fsdevel@vger.kernel.org, fuse-devel , linux-mm , miklos , Gabriel Krisman Bertazi , =?utf-8?Q?Andr=C3=A9?= Almeida Subject: fuse: trying to steal weird page Mail-Copies-To: never Mail-Followup-To: linux-fsdevel@vger.kernel.org, fuse-devel , linux-mm , miklos , Gabriel Krisman Bertazi , =?utf-8?Q?Andr=C3=A9?= Almeida Date: Sat, 02 May 2020 20:09:23 +0100 Message-ID: <87a72qtaqk.fsf@vostro.rath.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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: Hello, I have recently noticed that a FUSE filesystem regularly produces many kernel messages like this: [ 2333.009931] fuse: trying to steal weird page [ 2333.009937] fuse: page=3D00000000dd1750e3 index=3D2022240 flags=3D17ff= ffc0000097, count=3D1, mapcount=3D0, mapping=3D00000000125079ad [ 2334.595835] fuse: trying to steal weird page [ 2334.595841] fuse: page=3D000000009e8626ac index=3D2052288 flags=3D17ff= ffc0000097, count=3D1, mapcount=3D0, mapping=3D00000000125079ad [ 2334.983568] fuse: trying to steal weird page [ 2334.983572] fuse: page=3D0000000013fdd9e4 index=3D2059392 flags=3D17ff= ffc0000097, count=3D1, mapcount=3D0, mapping=3D00000000125079ad [ 2335.979905] fuse: trying to steal weird page [ 2335.979911] fuse: page=3D00000000a7057848 index=3D2078588 flags=3D17ff= ffc0000097, count=3D1, mapcount=3D0, mapping=3D00000000125079ad They do not seem to correlate with userspace errors, but I noticed that there is no significant performance difference between libfuse using splice, splice with SPLICE_MOVE, and not using splice. This is somewhat unexpected, so maybe it is related to the kernel messages? What are the implications of the above kernel message? Is there a way to provide more debugging information? (I have reported a similar issue before (https://marc.info/?l=3Dlinux-mm&m=3D155290847909996&w=3D2) and the patch m= ay not be present in the kernel that I'm using. However, the previous time the warning had a different set of flags and a null mapping, so I think this one is different). $ uname -a Linux valve 5.3.0-46-generic #38-Ubuntu SMP Fri Mar 27 17:37:05 UTC 2020 x8= 6_64 x86_64 x86_64 GNU/Linux Best, -Nikolaus --=20 GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F =C2=BBTime flies like an arrow, fruit flies like a Banana.=C2= =AB