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=-12.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 32B35C64E7A for ; Thu, 3 Dec 2020 04:51:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D495222243 for ; Thu, 3 Dec 2020 04:51:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727529AbgLCEvc (ORCPT ); Wed, 2 Dec 2020 23:51:32 -0500 Received: from mout.gmx.net ([212.227.17.21]:59325 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725933AbgLCEva (ORCPT ); Wed, 2 Dec 2020 23:51:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1606970965; bh=vtY3Qi8NpGKMNFi0hzBZF35FXjvnB7XQst/wBtXkN3k=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=hOY33hRyU8JkPQaA4wjNNv3WjxV11tKIxBW2jcIZX30pXUYQVSs7FtVEiv/mMZcPv M9MBqXQ/Pa2I5yjSxdIHms6ezfP6P74t95FnQO9AI0doGsgbsI9AcTS5vhZ9GJPDud CzhmgRYGp/QA5VbZf57arMVBwHfQcwxzs+asHPIs= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [0.0.0.0] ([149.28.201.231]) by mail.gmx.com (mrgmx104 [212.227.17.174]) with ESMTPSA (Nemesis) id 1Mt79F-1js1da3c1B-00tPSM; Thu, 03 Dec 2020 05:49:25 +0100 Subject: Re: [PATCH v3 30/54] btrfs: validate ->reloc_root after recording root in trans To: Josef Bacik , linux-btrfs@vger.kernel.org, kernel-team@fb.com Cc: Zygo Blaxell References: <60d12b7256e6877061eaa9df99ce2ed1f0f3d012.1606938211.git.josef@toxicpanda.com> 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 AAG0IlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT6JAU4EEwEIADgCGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCXZw1oQAKCRDC PZHzoSX+qCY6CACd+mWu3okGwRKXju6bou+7VkqCaHTdyXwWFTsr+/0ly5nUdDtT3yEVggPJ 3VP70wjlrxUjNjFb6iIvGYxiPOrop1NGwGYvQktgRhaIhALG6rPoSSAhGNjwGVRw0km0PlIN D29BTj/lYEk+jVM1YL0QLgAE1AI3krihg/lp/fQT53wLhR8YZIF8ETXbClQG1vJ0cllPuEEv efKxRyiTSjB+PsozSvYWhXsPeJ+KKjFen7ebE5reQTPFzSHctCdPnoR/4jSPlnTlnEvLeqcD ZTuKfQe1gWrPeevQzgCtgBF/WjIOeJs41klnYzC3DymuQlmFubss0jShLOW8eSOOWhLRuQEN BFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcgaCbPEwhLj 1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj/IrRUUka 68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fNGSsRb+pK EKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0q1eW4Jrv 0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEvABEBAAGJ ATwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCXZw1rgUJCWpOfwAKCRDCPZHz oSX+qFcEB/95cs8cM1OQdE/GgOfCGxwgckMeWyzOR7bkAWW0lDVp2hpgJuxBW/gyfmtBnUai fnggx3EE3ev8HTysZU9q0h+TJwwJKGv6sUc8qcTGFDtavnnl+r6xDUY7A6GvXEsSoCEEynby 72byGeSovfq/4AWGNPBG1L61Exl+gbqfvbECP3ziXnob009+z9I4qXodHSYINfAkZkA523JG ap12LndJeLk3gfWNZfXEWyGnuciRGbqESkhIRav8ootsCIops/SqXm0/k+Kcl4gGUO/iD/T5 oagaDh0QtOd8RWSMwLxwn8uIhpH84Q4X1LadJ5NCgGa6xPP5qqRuiC+9gZqbq4Nj Message-ID: <81983f16-ce45-dfbd-4b91-ac6970209fc6@gmx.com> Date: Thu, 3 Dec 2020 12:49:19 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <60d12b7256e6877061eaa9df99ce2ed1f0f3d012.1606938211.git.josef@toxicpanda.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="oFuIeoPQhMAFRLNHblivhMTJEosNjHZGG" X-Provags-ID: V03:K1:30aa/x4zpERzLfkwiBT1JFv7SSbFjWsL8yEOaKM1oCrzBsceG9L kafqHOYAMqEeVDXXVZy7LmM6Q1RQzPLb+Q/CctbGeJxGtD8Zq1jtk8Zsgx1i1F1zJM6loL9 6tiKPUIYWu9byFTPgMWEBt0ljl+EznrwK1R9cJhglqbPMRBWLMu2xmQzVy56E2WaB4Dsqto /+Im4Set0A8qpY2TKHRhw== X-UI-Out-Filterresults: notjunk:1;V03:K0:ovotnegNQvE=:M1qRp2WOSZO9UzUBncgi4C fnYKe3vyQMM3l4dfvJEfbsiq+lDqyYwAOnSe8MKmMX9ggn7ZlqbPJ5lQYW7r4yMTrx6sgvFQg F1uzlg3+obPwI3WTCm7kELJis5HX9vbSItnAliHx5OoPPwPu4s3+yJuX32s2utnbN2MNhndIM GpwEj9WYnwPIewQYlpTte47vqcvHSH5sXXPaftH6KaK4xI7dhbZJ8SF68TbrGefmIeOOBa/RV hzd2dXFgKyehogCLuvWLxNdIUXOrLUd9PTBSXQdHhnZUqp6iVdZQBX6T/qyfLJAxfBbUpBFu2 /vcyXofoQBEWzl+9znR0mPKoycGU4u7XETnvURuPlgzcHoLl5xoolDyKKSAp44I5wip1I5X1P m/MXqFqYQdHA3rZFdWDm5Au+hvAkb0uwMGfL/w/GySwZ1xv/mZyVzcjOq6RbQ0X8ikIBWkO/F CTEaleQZVc8aDDZzR/pycEwlX+/tkUgvT6Qhg/Fu/3WMeUp3BK0NN918lh7mjKtlfVpblqogz EF2Ak+gNgs+HaU2pbie6IjJPdI+tTVk5ez14ERG8AitQze2mRgciai3rtSido4FXFdn/QyDpk +WUA3UPUZOy3jAsr/a/l9o5Qd17BysrDmL3klmM8xoMwp1rCsr1fsm+qSbdJ4m9LjbBNyJdo1 IfJoNl8rU8U/Qe34yGqJq2O/PPJ735ClpecKCVrL7sI01n8b6Os6tAXWMPYvqnWK1U6PL5dqU QMFx643AY28swKNYzQL94XOkMXQr/xMRS5JGts9eLHzLwxUbIp6UCzxhqos5M3UHa0vuXIRlh lAw4HtORJV1Q6OWyBCf7v2s06/JjBKRGrVkf1r1DrMl52QDokHcLsebfusYgCzfO6IDC7KpHS 9WG3RnPbv+PopxDcw3RA== Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --oFuIeoPQhMAFRLNHblivhMTJEosNjHZGG Content-Type: multipart/mixed; boundary="PBj9hK8aw1EcnkP1jymTI8ZX0P6g5CROx" --PBj9hK8aw1EcnkP1jymTI8ZX0P6g5CROx Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2020/12/3 =E4=B8=8A=E5=8D=883:50, Josef Bacik wrote: > If we fail to setup a ->reloc_root in a different thread that path will= > error out, however it still leaves root->reloc_root NULL but would stil= l > appear set up in the transaction. Subsequent calls to > btrfs_record_root_in_transaction would succeed without attempting to > create the reloc root, as the transid has already been update. Handle > this case by making sure we have a root->reloc_root set after a > btrfs_record_root_in_transaction call so we don't end up deref'ing a > NULL pointer. >=20 > Reported-by: Zygo Blaxell > Signed-off-by: Josef Bacik The fix here is mostly based on the fact that pointer assignment is atomi= c. But I'm wondering if we can do it better by using something like spinlock to make it more explicit. Or is such root->reloc_lock too overkilled? Thanks, Qu > --- > fs/btrfs/relocation.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) >=20 > diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c > index cebf8e9d7d96..c9df05f02649 100644 > --- a/fs/btrfs/relocation.c > +++ b/fs/btrfs/relocation.c > @@ -2078,6 +2078,13 @@ struct btrfs_root *select_reloc_root(struct btrf= s_trans_handle *trans, > return ERR_PTR(ret); > root =3D root->reloc_root; > =20 > + /* > + * We could have raced with another thread which failed, so > + * ->reloc_root may not be set, return -ENOENT in this case. > + */ > + if (!root) > + return ERR_PTR(-ENOENT); > + > if (next->new_bytenr !=3D root->node->start) { > /* > * We just created the reloc root, so we shouldn't have > @@ -2579,6 +2586,14 @@ static int relocate_tree_block(struct btrfs_tran= s_handle *trans, > ret =3D btrfs_record_root_in_trans(trans, root); > if (ret) > goto out; > + /* > + * Another thread could have failed, need to check if we > + * have ->reloc_root actually set. > + */ > + if (!root->reloc_root) { > + ret =3D -ENOENT; > + goto out; > + } > root =3D root->reloc_root; > node->new_bytenr =3D root->node->start; > btrfs_put_root(node->root); >=20 --PBj9hK8aw1EcnkP1jymTI8ZX0P6g5CROx-- --oFuIeoPQhMAFRLNHblivhMTJEosNjHZGG Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEELd9y5aWlW6idqkLhwj2R86El/qgFAl/Ibk8ACgkQwj2R86El /qjwlwf/U9UjYet/EswetNxfMgNxwIM8RDXpOCCrhcKeZ3w2pFrd2csKjMmnYceD EqsgzWFfNYRYub7uypCE5/b5WfOc7qXpTmbfWdsCXWtLrF/I61iZ141ByUg9cgO4 PYukNlUkXj6Wvyq9kh8W1upcMN88mFellx3b/NxdkrzeKi4zt3IDYnK+eq2mxaI2 4/R32M/Lvoim5ArGJVtm5/GbbwOlwcB3UJTaE8l1UQ9kK1fpzEwrMb8lOneZ35El 8kSc81WgfgX8rmTZSCwMIwnu1G+yR9fCFqPOgmjmpJuJdRggO7qEJvPigai37cUA TWIEwaomFUEm4pPfQu4oMfu+85zRcg== =g9FJ -----END PGP SIGNATURE----- --oFuIeoPQhMAFRLNHblivhMTJEosNjHZGG--