From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f67.google.com ([209.85.160.67]:32856 "EHLO mail-pl0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750718AbeE2EM0 (ORCPT ); Tue, 29 May 2018 00:12:26 -0400 Date: Tue, 29 May 2018 12:57:03 +0900 From: Jungsub Shin To: Al Viro Cc: "J. R. Okajima" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, aufs-users@lists.sourceforge.net Subject: Re: Why is the length of max mount option a page size?? Message-ID: <20180529035703.GA32550@supsup-VirtualBox> References: <20180521173959.GA12779@supsup-VirtualBox> <5670.1527244930@jrobl> <20180529002456.GA30767@supsup-VirtualBox> <20180529011412.GE30522@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: <20180529011412.GE30522@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, May 29, 2018 at 02:14:12AM +0100, Al Viro wrote: > On Tue, May 29, 2018 at 09:24:56AM +0900, Jungsub Shin wrote: > > Mount command : mount -t aufs -o br=3D~/tca_agent/container_rw_dir/5150= 9032=3Drw:~/tca_agent/image_layer_dir/5a259d94211e449fd466d997b5b0b149cb299= 7a732fd3a838c14295e0eb93f92=3Dro+wh:~/tca_agent/image_layer_dir/faca908333f= 884648b75738571879df977339ee7615c65410c98001a463bcd00=3Dro+wh:~/tca_agent/i= mage_layer_dir/67b50813aedeb67fd06b434163fa64d07fbd16f714196daea1cd139a0171= 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/image_layer_dir/0c65112ac5c572a950e2671f903ef11e918e6e3cdbf026edda90db6c7a= 9c6ef8=3Dro+wh:~/tca_agent/image_layer_dir/ce16b72d243b82ded684a547da1400b8= f2d07ed7b36b114ae0cbe2f20c17b0bf=3Dro+wh:~/tca_agent/image_layer_dir/a3937b= 112d7dbedfe075162862e404b7b85803d880589eaf3ebad9855629bdd5=3Dro+wh:~/tca_ag= ent/image_layer_dir/b486d646cd9f5b8151856133ea3e81d53c3664bb727a0a87d0197cb= bae9211de=3Dro+wh:~/tca_agent/image_layer_dir/de1b712fcfedbc3f61248c1a5fb9c= ba5a5ab6c7415f2c71c7ea162fd7c738c6f=3Dro+wh:~/tca_agent/image_layer_dir/295= 8a858559d3091b8162c066cfe5e17012f2307772180e702ffbc89bcae8fc2=3Dro+wh:~/tca= _agent/image_layer_dir/14eae848ef41eb275ad37cc9d12dc276d3f08beeb06e04140737= 1b9489335ee1=3Dro+wh:~/tca_agent/image_layer_dir/d72e07c403501a4abefaa80f3b= 81121392c42f314fc14bbf1bb434dc84457dd5=3Dro+wh:~/tca_agent/image_layer_dir/= ee0efde24e35b4e2f801ca25640169ca2f319f9b5d37dbb0917cfd43e818d1f4=3Dro+wh:~/= tca_agent/image_layer_dir/67dfb4d7c7ce39829d36740e1ef5279e00320a0d2bfe06bb6= 7b6571f1ff47627=3Dro+wh:~/tca_agent/image_layer_dir/b3a1a69310f719755232ed5= f8509f11f549d620d723ea293f001e3d30795108b=3Dro+wh:~/tca_agent/image_layer_d= ir/a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4=3Dro+wh= :~/tca_agent/image_layer_dir/e5ad7970bc69d2ba62d2bbb4b80627273350e1982ff43b= c1ca04a3215bc6da5b=3Dro+wh none ~/tca_agent/container_root_dir/51509032 > > dmesg : [343090.744067] aufs opt_add:810:mount[30864]: lookup failed /r= oot/tca_agent/image_layer_di (-2) I think kernel at least must print warning message when mount option=20 overflow the PAGE_SIZE if length of mount option should be fixed.=20 When i encouter this problem, i found the reason hard because of=20 lack of kernel log and wrong infomation. > > ------------------------------------------------------------------------ > >=20 > > br option is cut and aufs search cut directory. Length of mount option > > is about 6400. >=20 > The lack of planning on your part... >=20 > IOW, don't do it. Use of symlinks (or bindings) might alleviate the prob= lem > if aufs interface is that nasty. And before you go "just read up to \0", > consider e.g. NFS flavours with binary data structure passed instead of > a string. Do you mean using symlinks or bind mount to reduce length of mount options?? I can remove "~/tca_agent/image_layer_dir" string. But the other character means unique ID of layer and i can't compress it or replace it to another string. This is not fundamental solution. Docker=20 use the same unique ID to manage layers.=20 As i said before overlayfs could suffer same problem because overlayfs=20 support multiple lowerdir options and there is no route to pass lower dirs without mount option. So i think to support unionfs stably in kernel, dynamic memory allocation for mount option is needed. Thanks.