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=-6.7 required=3.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 EF6C3C43441 for ; Tue, 20 Nov 2018 00:34:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B2CB52080C for ; Tue, 20 Nov 2018 00:34:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B2CB52080C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=gmx.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-btrfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732190AbeKTLAZ (ORCPT ); Tue, 20 Nov 2018 06:00:25 -0500 Received: from mout.gmx.net ([212.227.17.20]:58197 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731351AbeKTLAY (ORCPT ); Tue, 20 Nov 2018 06:00:24 -0500 Received: from [0.0.0.0] ([149.28.201.231]) by mail.gmx.com (mrgmx103 [212.227.17.174]) with ESMTPSA (Nemesis) id 0Lq9Ma-1flQQy0bfE-00drXc; Tue, 20 Nov 2018 01:34:01 +0100 Subject: Re: [PATCH] Btrfs: fix race between enabling quotas and subvolume creation To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org References: <20181119162034.13132-1-fdmanana@kernel.org> From: Qu Wenruo Openpgp: preference=signencrypt Autocrypt: addr=quwenruo.btrfs@gmx.com; prefer-encrypt=mutual; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWCnQUJCWYC bgAKCRDCPZHzoSX+qAR8B/94VAsSNygx1C6dhb1u1Wp1Jr/lfO7QIOK/nf1PF0VpYjTQ2au8 ihf/RApTna31sVjBx3jzlmpy+lDoPdXwbI3Czx1PwDbdhAAjdRbvBmwM6cUWyqD+zjVm4RTG rFTPi3E7828YJ71Vpda2qghOYdnC45xCcjmHh8FwReLzsV2A6FtXsvd87bq6Iw2axOHVUax2 FGSbardMsHrya1dC2jF2R6n0uxaIc1bWGweYsq0LXvLcvjWH+zDgzYCUB0cfb+6Ib/ipSCYp 3i8BevMsTs62MOBmKz7til6Zdz0kkqDdSNOq8LgWGLOwUTqBh71+lqN2XBpTDu1eLZaNbxSI ilaVzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWBrwIbDAUJA8JnAAAK CRDCPZHzoSX+qA3xB/4zS8zYh3Cbm3FllKz7+RKBw/ETBibFSKedQkbJzRlZhBc+XRwF61mi f0SXSdqKMbM1a98fEg8H5kV6GTo62BzvynVrf/FyT+zWbIVEuuZttMk2gWLIvbmWNyrQnzPl mnjK4AEvZGIt1pk+3+N/CMEfAZH5Aqnp0PaoytRZ/1vtMXNgMxlfNnb96giC3KMR6U0E+siA 4V7biIoyNoaN33t8m5FwEwd2FQDG9dAXWhG13zcm9gnk63BN3wyCQR+X5+jsfBaS4dvNzvQv h8Uq/YGjCoV1ofKYh3WKMY8avjq25nlrhzD/Nto9jHp8niwr21K//pXVA81R2qaXqGbql+zo Message-ID: <25aa831b-5562-aaab-ef69-ef3e45c81fc4@gmx.com> Date: Tue, 20 Nov 2018 08:33:57 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 MIME-Version: 1.0 In-Reply-To: <20181119162034.13132-1-fdmanana@kernel.org> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ZRBZs2IQ3rhnzt83VXLfiYZaAZAbnboQ3" X-Provags-ID: V03:K1:2EJO0m7LddmbfC096Vhvzbz9JBKKfrqJBtARCG1iFOJo3H2MKoa mdV8E+l5ECh1AxDW435dD5P2IHAyse8SfmdzjGK9lcT/dbUG1uMLCTxzkkwWEojCQy01EmP u9bwzRf+4dpLclhFj14c2sfpoiwQQsMrlD59WS7SYeM80Kf2BXrbC1EXXyFghAL46ngrwLA z7ksGUw9y2MRHOi7q9p3g== X-UI-Out-Filterresults: notjunk:1;V01:K0:8PN/PxRpmNk=:eH04/vcG/8nzyvb8wiJK5E iZVfBzOyS+1McA0GWcvy0LkmGcYpZ5CD+e2TfJX9jks8KhSTNCRt+lAhwn8lrUgs5CvXebKrI GaSEavb5X5y38S6YoYirI2fU6tcKxlbWh+1kKbh+miz5+SgCruLg7rbQXy+sEh39Ul1Ujvgx7 iGXW/fL8pH7xtWqHueJYuoUjK+cE1vispnU8CMuqY22+JlKZ2LYpiLg5VPvDRWG++AWl28pFY M0c6JXgQ+bcC1rYE2jkt8l15m5M5/o+BI8scBA+0Ur3McKmwaaoTnZsGXW2ljhwG8rTSeqo7E td1yi9ryJTyhTxYRGziwFeXLdAyi7lcQClZj7bBVHKD+uaBAbVQ00+TjQRfa3kdOThJut7z/e k3jzmAx1fRWJWy9L8Jp2FVcnIaqUuHQr16kXMrQT1yKEyp9KPpQW7cji4FDU9u/fPkyCiXmRk 5jLfQR5ptfSs2YvVdvC/2LHEGxVpiI3NOagp5co0ZZZAP7vLLnZmH6IFm2KERCkoZ3YJRk/w8 u05cwzZACI51JXFKuq5raNKjIjUQtgNb0PDC/6tFEVdnG9E9PiB7kCxOmNesLF6qF/gtx2HhF Iv2owwaOhtxygeMEtls4qiL9CF0ocDlvi/0SgmiA12/0+RKvtMc7NhoEHPLT5gIA2yB7tqUPp ksS2+/b1EBYKG8j90pJK1GKwroKWePc2VDv4Tn36wFcfG2u84HWQ3bBz2kg3LtGkN4L5Vaw6u 7OhxjPoqDKOXWznRaf1caRBf9youkTpc0FdKjmi4RVBpH04l6L5KaFa+NbUZ+35KSlGttLK+F nQGOMJC2rFQBBhwNphQ1CxziVaIk8pJxYvFcwhz/ha0/byWOSCKrQSKdODXde14yuVS4rnSOS zGf4VCg4GtnR+D6MnB5pogYmOGRTrT2ltMawYGBPurbZa+s6HD/vUU0Ku/lBDj Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --ZRBZs2IQ3rhnzt83VXLfiYZaAZAbnboQ3 Content-Type: multipart/mixed; boundary="e5AtejLN1BEm6ML0PtIloWT9Lia45hF6b"; protected-headers="v1" From: Qu Wenruo To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org Message-ID: <25aa831b-5562-aaab-ef69-ef3e45c81fc4@gmx.com> Subject: Re: [PATCH] Btrfs: fix race between enabling quotas and subvolume creation References: <20181119162034.13132-1-fdmanana@kernel.org> In-Reply-To: <20181119162034.13132-1-fdmanana@kernel.org> --e5AtejLN1BEm6ML0PtIloWT9Lia45hF6b Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2018/11/20 =E4=B8=8A=E5=8D=8812:20, fdmanana@kernel.org wrote: > From: Filipe Manana >=20 > We have a race between enabling quotas end subvolume creation that caus= e > subvolume creation to fail with -EINVAL, and the following diagram show= s > how it happens: >=20 > CPU 0 CPU 1 >=20 > btrfs_ioctl() > btrfs_ioctl_quota_ctl() > btrfs_quota_enable() > mutex_lock(fs_info->qgroup_ioctl_lock) >=20 > btrfs_ioctl() > create_subvol() > btrfs_qgroup_inheri= t() > -> save fs_info->q= uota_root > into quota_root= > -> stores a NULL v= alue > -> tries to lock t= he mutex > qgroup_ioctl_lo= ck > -> blocks waiti= ng for > the task at = CPU0 >=20 > -> sets BTRFS_FS_QUOTA_ENABLED in fs_info > -> sets quota_root in fs_info->quota_root > (non-NULL value) >=20 > mutex_unlock(fs_info->qgroup_ioctl_lock) >=20 > -> checks quota en= abled > flag is set > -> returns -EINVAL= because > fs_info->quota_= root was > NULL before it = acquired > the mutex > qgroup_ioctl_lo= ck > -> ioctl returns -EI= NVAL >=20 > Returning -EINVAL to user space will be confusing if all the arguments > passed to the subvolume creation ioctl were valid. >=20 > Fix it by grabbing the value from fs_info->quota_root after acquiring > the mutex. >=20 > Signed-off-by: Filipe Manana Reviewed-by: Qu Wenruo Thanks, Qu > --- > fs/btrfs/qgroup.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c > index ae1358253b7b..0bdf28499790 100644 > --- a/fs/btrfs/qgroup.c > +++ b/fs/btrfs/qgroup.c > @@ -2250,7 +2250,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handl= e *trans, u64 srcid, > int i; > u64 *i_qgroups; > struct btrfs_fs_info *fs_info =3D trans->fs_info; > - struct btrfs_root *quota_root =3D fs_info->quota_root; > + struct btrfs_root *quota_root; > struct btrfs_qgroup *srcgroup; > struct btrfs_qgroup *dstgroup; > u32 level_size =3D 0; > @@ -2260,6 +2260,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handl= e *trans, u64 srcid, > if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)) > goto out; > =20 > + quota_root =3D fs_info->quota_root; > if (!quota_root) { > ret =3D -EINVAL; > goto out; >=20 --e5AtejLN1BEm6ML0PtIloWT9Lia45hF6b-- --ZRBZs2IQ3rhnzt83VXLfiYZaAZAbnboQ3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEELd9y5aWlW6idqkLhwj2R86El/qgFAlvzVnUACgkQwj2R86El /qjrCQf/TPwAyTQwF3ecH+P7WVspYRKMtp6QQQTfM5MLOVj+WoBaiYvIqzIiZQT7 rO2e6lzAQcv2++SSt9atGoOnLJRLiWjyEJJa578/WxfJkkWWs+e1WFpa907vNDi1 DFHWzmBDBB4fDiUnKQ2ELEMcIzYkFoE1mwzMydmATwZLcKcC3Ws7P95ZO9C+TBdZ B6xFlS5B9Yd6dyD0WPb0oA7jDgEGqn2eX9ld2vJRTsnD6VGqkzW9jp5xwaWNhe/O j6PgD92swVshq5YR5c5C0g5I8/PZy55dr1p4tYHhS8gtoJIK2igYXCK+qeKLXF0X wRKvpML3ZpYvzZEnZc71qCYXS/cZpA== =FJ92 -----END PGP SIGNATURE----- --ZRBZs2IQ3rhnzt83VXLfiYZaAZAbnboQ3--