From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68658C433E0 for ; Wed, 12 Aug 2020 06:33:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3767C20768 for ; Wed, 12 Aug 2020 06:33:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=gmx.net header.i=@gmx.net header.b="Ml8zcXku" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726716AbgHLGds (ORCPT ); Wed, 12 Aug 2020 02:33:48 -0400 Received: from mout.gmx.net ([212.227.15.19]:38525 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726572AbgHLGdr (ORCPT ); Wed, 12 Aug 2020 02:33:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1597214020; bh=PkFcZagO2Zi2wFBD2IgBPTZGGkg9aYUUsLwL+GyAK3w=; h=X-UI-Sender-Class:Subject:To:References:From:Date:In-Reply-To; b=Ml8zcXku5pEzZk4Mg6XrOOZM4i5DwRDuik5g3RqEhxa/71oWFGpfd7343Ww6mdqq/ +h5xEP+LJJxVsMbKKL51mE8vQ6TPkmEE7NtbfrLr2jWmJh82d+JirzSR8wXfKemeaQ F/RCCaGFewHGWsCofao7rOBtp0omP/X2ThlAqiLE= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [0.0.0.0] ([45.77.180.217]) by mail.gmx.com (mrgmx005 [212.227.17.184]) with ESMTPSA (Nemesis) id 1N8GQs-1kjKKo3TZQ-014Gbu; Wed, 12 Aug 2020 08:33:40 +0200 Subject: Re: [PATCH v4] btrfs: trim: fix underflow in trim length to prevent access beyond device boundary To: dsterba@suse.cz, Qu Wenruo , linux-btrfs@vger.kernel.org, Filipe Manana References: <20200731112911.115665-1-wqu@suse.com> <20200731140807.GM3703@twin.jikos.cz> <9ec86d30-96b5-2e80-969e-158342c273ab@gmx.com> <20200811072234.GK2026@twin.jikos.cz> <8796039b-d0b1-a129-3b01-a260a051154b@gmx.com> <20200812061016.GT2026@twin.jikos.cz> From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; prefer-encrypt=mutual; keydata= mQENBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAG0IlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT6JAVQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWCnQUJCWYC bgAKCRDCPZHzoSX+qAR8B/94VAsSNygx1C6dhb1u1Wp1Jr/lfO7QIOK/nf1PF0VpYjTQ2au8 ihf/RApTna31sVjBx3jzlmpy+lDoPdXwbI3Czx1PwDbdhAAjdRbvBmwM6cUWyqD+zjVm4RTG rFTPi3E7828YJ71Vpda2qghOYdnC45xCcjmHh8FwReLzsV2A6FtXsvd87bq6Iw2axOHVUax2 FGSbardMsHrya1dC2jF2R6n0uxaIc1bWGweYsq0LXvLcvjWH+zDgzYCUB0cfb+6Ib/ipSCYp 3i8BevMsTs62MOBmKz7til6Zdz0kkqDdSNOq8LgWGLOwUTqBh71+lqN2XBpTDu1eLZaNbxSI ilaVuQENBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAGJATwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCXZw1rgUJCWpOfwAK CRDCPZHzoSX+qFcEB/95cs8cM1OQdE/GgOfCGxwgckMeWyzOR7bkAWW0lDVp2hpgJuxBW/gy fmtBnUaifnggx3EE3ev8HTysZU9q0h+TJwwJKGv6sUc8qcTGFDtavnnl+r6xDUY7A6GvXEsS oCEEynby72byGeSovfq/4AWGNPBG1L61Exl+gbqfvbECP3ziXnob009+z9I4qXodHSYINfAk ZkA523JGap12LndJeLk3gfWNZfXEWyGnuciRGbqESkhIRav8ootsCIops/SqXm0/k+Kcl4gG UO/iD/T5oagaDh0QtOd8RWSMwLxwn8uIhpH84Q4X1LadJ5NCgGa6xPP5qqRuiC+9gZqbq4Nj Message-ID: <2fd35a06-ba26-173d-1b72-e41243b78068@gmx.com> Date: Wed, 12 Aug 2020 14:33:33 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200812061016.GT2026@twin.jikos.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:Xxt3K8AhxI5RMa8BQflFAfCIOFcE0PerwNj1EgZX/H7DjbIgZYl pEXYUFk4QjYm5wHRbyW5RccO+4n+AWiGprENd6pjxuS8cvDvIHlqL2RFMylC0UdOO9sFWRe W1WaOZUXGUhV8nWd2wdreoiHPc7eJs65M1O7Gy1haIEgGi4nS3Pt/FbfpZNqe+5pjFKmwO2 1Ej5tF209FF/mayJbFoJQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:/iWjsPWlD5I=:CjEvKCjMj/dBOA4O//v/wv 3bAY9AsCxxtnVkerGWjdI6h8HIfKZerN737cYmC6L8heXsOPibwYVqiUFNrRmcu7NtwqrToKp mM+ykK9zwIaBssjZMy8U1ksDmKnIiFAlFhCyZR9Y3CFlRDMT5DZO0YJMbRloSfCp+Ymym/Hay gYWXT6j7nnBmjNk6XGmfypCWXGgIMlYMhs2sjk+s6bQiviHA4Bq6PMMgVHcRNqWaUrI3bdE9x dIFbIuWK+BV0+sIlDOONa4RaO9MbJkUVJnBBBKjLhjNn+nVl0eEwIULhL7XLh2xp8NAb/9bs5 Q67ZhRsvXvMO0dPtpltD9KczXPbJ7cGzLtZO97N8pwEmEvT5OhzqIPm/+YnS9kSlReCTpRdxc vxcjPH02rUtENArhEbZkSyqpumnaZU3xvOwuj50GQzb5O2HMWoTjE0BAqKxhyhztZ4MHY5MES nt3WTw2p/aO68E8aGK3fTqQu7nrZFV7vOzEUE93RpT5edOhMCkuIulJhmne+nXMUFjBDLi4yB M06X6seQYQPd+CURlUyqqQYOyqaowzyzV/5o1J5/TlPZJb+2lV55VaprpDXMWoW+HQrhFd5fn FBOZGujnulhRmby7n6vNiCbVek3GYsfuOWGrb7aD7wv7P7aFwhnApNXkGA3eNZu7p7K4OS8sV 1n+CA7AkckKSfb+lP3AqpazTq7N9rLcHz9RhSWmbgeIrpaXY4aB3Pve6B2r2fAE6INFu57cpt in544zR0y32HzlICpBS5yKP+QybK+DR82tsflU+74XccWT7ZnM3WopWpdjgOPSI4JLcH5nPwE SdaeAerxHwiS5YB3hB9BaJz4iS+3Rvl/z1GkO5KE6l4jWRRhfPYpYL9iQfQrY1fErrHtVELbS q9Qt+EtFNX/OJHQJhbXRz8f0zPo0X8sBcSZKrJq4qtqVBrresbwHCX+08HAUYNQA7wLr8+mRB LIo0rFq1nVt5LOdBO0I3mvSUW9GsUKGbh31ByZR4gLfG/wOvFVuEmoUfpxHezEoKV2zeSZFBp po2QzhAbvHZpQn/sXp9bFnXCtsUnebSrUSFBrtL3AzozvqQEyHBs8deuMSnspbHNs93FUBO20 hgxyWCBcqmw+l6jgbCAK81/7fi5sI/oE0askBBWKuvchIASphll/zcwFquU5lISNucLhC3nbW +FnJ/Dg+uBMIWv5tM1aOGMC7fNv6SpU9TLnBfEtpXOMrTtp0ueKjO9HVLMy1A7COAc6XHUua5 6foqgnu67062BH54YPid4y2UDMwwmgVNFy42cKQ== Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2020/8/12 =E4=B8=8B=E5=8D=882:10, David Sterba wrote: > On Tue, Aug 11, 2020 at 03:42:31PM +0800, Qu Wenruo wrote: >>>> CHUNK_TRIMMED and CHUNK_ALLOCATED. >>>> >>>> Thus what we're doing is to clear all utilized bits. >>> >>> Which is true for now, adding a new bit would change that. >> >> Yep, that's also why I had the comment here. > > The comment is not enough to make the code future proof, as we really > want do clear all bits in the range beyond device->total_size and that > works only if we specify them all (clear_state_bit). > > Either we can define a bitmask of all the bits next to their definition > (slightly more error prone if we forget to add that manually), or pass a > all ones to the clear_extent_bit. Though this is a bit uncommon, with a > comment I'd prefer this option. OK, I'd go that (u64)-1 as clear_bits direction, with updated comment. Thanks, Qu > >>>>> But I still have doubts about just clearing the range, why are there= any >>>>> device->alloc_state entries at all after device is shrunk? >>>> >>>> Because the alloc_state is mostly only utilized by trim facility, thu= s >>>> existing functions won't bother clearing/setting it. >>>> >>>> In this particular case, previous fstrim run would set the CHUNK_TRIM= MED >>>> bit for all unallocated range (except the super reserve). >>>> Then shrink doesn't clear the exceed range, and cause problem. >>> >>> So the unallocated range on a device is also represented in the >>> alloc_state tree? >> >> If the unallocated range has been trimmed, then it has an state, with >> CHUNK_TRIMMED bit set. > > To clarify my previous doubts: I was talking about the slack space (ie. > space beyond device->total_size up to block device size), 'unallocated' > is ambiguous and confusing here. > > The missing bit about clearing the whole range lies inside > clear_state_bit that deletes all state tracking once all bits are > dropped. >