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Mon, 23 Nov 2020 21:42:58 -0500 Received: from mout.gmx.net ([212.227.17.22]:44161 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728491AbgKXCm5 (ORCPT ); Mon, 23 Nov 2020 21:42:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1606185769; bh=X2BRwyvbi3RV7HhzhkudubrPU4sbgQhX+TQ3pG9ETe4=; h=X-UI-Sender-Class:Subject:To:References:From:Date:In-Reply-To; b=RDzGPv4ddMpHj4Vn2Wp68MEdGL++9A36gyJpuuveZbY031W1jcnlhCR3OzdWqpKB/ OW46KXYGFVas5NBZ6PN18081h1gf1j51qcVYQBeYt0W+SaQERi5wSPKNuDl44lIvt2 Z7VFz5o1kS9iR1HHDR1rM6Gesv9mNgEH+LgmCNNo= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [0.0.0.0] ([149.28.201.231]) by mail.gmx.com (mrgmx105 [212.227.17.174]) with ESMTPSA (Nemesis) id 1MGQj7-1kR7w53nVF-00GnzP; Tue, 24 Nov 2020 03:42:49 +0100 Subject: Re: [PATCH] btrfs: fix lockdep splat when reading qgroup config on mount To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org References: <0343c1f0b12747805d837106ada99e10468363b6.1606141632.git.fdmanana@suse.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: <0f3ac26c-fdf4-4b5b-8b68-0bc48fe62826@gmx.com> Date: Tue, 24 Nov 2020 10:42:45 +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: <0343c1f0b12747805d837106ada99e10468363b6.1606141632.git.fdmanana@suse.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="DhqbbkehEJ5bq8ZfosRU7oowa4ra1jydK" X-Provags-ID: V03:K1:6mQcKyooJxGGzFOqZPU4E35YuJyEEmNUccpTJv/nHCFB9FmBTjP ZdZAX68aZ1EmVVC7Cj3CwxPdhuZMwBbQ0UK65tdP/7GZzoMv+X8OKZXrV+OeMzdk1xRXvWk y9n7peJiVSP+hxtlmgB6kz4VRuk5Gv4PLI5svHoa8GUzHGjlLhYpbdv9r4Jx0Si63+nVunm xDcsL7tA3/MJUwolxThCw== X-UI-Out-Filterresults: notjunk:1;V03:K0:GZNPBSc+YVk=:n1YnlI5j4a1Hpbd/R12smN OrKmpZilsrcI2nmeVQqmX6wZwTixDQ+wxIVTIjGHQ9nKMp9VRTs+ExF+4q+HMg3lL5c6416lD 7wd1iPZTEOq1o0aUWBlWRhShRKaL//C2edWOxM8ppAtGEbARpdtTdmjvAf7JCpBTfS5C2j8I1 c6h0aCCHVWmq7ntTZGSk05u8JQFeu2OjSUBpk6KqnuCSjEB7F7GM7qR0UXyghjCrEJ5yfbMWP hogh2vXK4hEKZTfIGYpxi1nd1gK4GP7HW7g2or2BH7yYLCjjy9AOU+/iNQa29t8JDNhaxM6wC yLHl7bR767W5SJQCblHbceTC5kGFGD4Eh+PCA7ZeI9QyNYdu0amDDEYA4dca81heOxxP4N1kF ldz5f2SHsBC7oX0HLF1VQhCViqEmjQs0DjYcjyow5VAz7o7GIzNOt58K/tMch7yMoTlkt4hNm KNwuLGpAcmdmNWbJB2sUX5ZEhbEevNIWOsBcLTmSBgcZABnTlDl9k3vJQzvCjVfwHzlAOIaKb rV1T5nWR6DJ4DSQcPTeiNVQgaQ+pkYuFK6mwqweQYvk95ue2V4dKKoCFHYw7yhU+ocTOK7gnm TrpivnTD9RagbG4boCiY6xWTprrBpNZNNyWchH6GSrNuU4f5OQXL9tu4S6uuJu5Ln90KR6/Qa z6WQtnwuay1yjz4tZi3pZHrOkAi1mVjLKzfmNNqG8heUfO50WeHWhex5tWUJ9KnwfCIHy+qq0 YqzPAyoZYXU8Tl8BfRhoAOfhsmXruUkhsGFRg/Q7d0RIRVt55kx6AGaq2KjVRkPDyg56hZPOK mQ/gm6MtrIzJsWlgABjjfLXDCNrSt0TwUR4KHwrXOPRP6pVueHxuf8O2f+WpuT2ea4bLVF60J oXufKqwRI8g5qDGS0wNw== Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --DhqbbkehEJ5bq8ZfosRU7oowa4ra1jydK Content-Type: multipart/mixed; boundary="zZwHFv8EwYZ8jqZ3WdXac6OYu0Kr6tvF0" --zZwHFv8EwYZ8jqZ3WdXac6OYu0Kr6tvF0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2020/11/23 =E4=B8=8B=E5=8D=8810:28, fdmanana@kernel.org wrote: > From: Filipe Manana >=20 > Lockdep reported the following splat when running test btrfs/190 from > fstests: >=20 > [ 9482.126098] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > [ 9482.126184] WARNING: possible circular locking dependency detected > [ 9482.126281] 5.10.0-rc4-btrfs-next-73 #1 Not tainted > [ 9482.126365] ------------------------------------------------------ > [ 9482.126456] mount/24187 is trying to acquire lock: > [ 9482.126534] ffffa0c869a7dac0 (&fs_info->qgroup_rescan_lock){+.+.}-{3= :3}, at: qgroup_rescan_init+0x43/0xf0 [btrfs] > [ 9482.126647] > but task is already holding lock: > [ 9482.126777] ffffa0c892ebd3a0 (btrfs-quota-00){++++}-{3:3}, at: __btr= fs_tree_read_lock+0x27/0x120 [btrfs] > [ 9482.126886] > which lock already depends on the new lock. >=20 > [ 9482.127078] > the existing dependency chain (in reverse order) is: > [ 9482.127213] > -> #1 (btrfs-quota-00){++++}-{3:3}: > [ 9482.127366] lock_acquire+0xd8/0x490 > [ 9482.127436] down_read_nested+0x45/0x220 > [ 9482.127528] __btrfs_tree_read_lock+0x27/0x120 [btrfs] > [ 9482.127613] btrfs_read_lock_root_node+0x41/0x130 [btrfs] > [ 9482.127702] btrfs_search_slot+0x514/0xc30 [btrfs] > [ 9482.127788] update_qgroup_status_item+0x72/0x140 [btrfs] > [ 9482.127877] btrfs_qgroup_rescan_worker+0xde/0x680 [btrfs] > [ 9482.127964] btrfs_work_helper+0xf1/0x600 [btrfs] > [ 9482.128039] process_one_work+0x24e/0x5e0 > [ 9482.128110] worker_thread+0x50/0x3b0 > [ 9482.128181] kthread+0x153/0x170 > [ 9482.128256] ret_from_fork+0x22/0x30 > [ 9482.128327] > -> #0 (&fs_info->qgroup_rescan_lock){+.+.}-{3:3}: > [ 9482.128464] check_prev_add+0x91/0xc60 > [ 9482.128551] __lock_acquire+0x1740/0x3110 > [ 9482.128623] lock_acquire+0xd8/0x490 > [ 9482.130029] __mutex_lock+0xa3/0xb30 > [ 9482.130590] qgroup_rescan_init+0x43/0xf0 [btrfs] > [ 9482.131577] btrfs_read_qgroup_config+0x43a/0x550 [btrfs] > [ 9482.132175] open_ctree+0x1228/0x18a0 [btrfs] > [ 9482.132756] btrfs_mount_root.cold+0x13/0xed [btrfs] > [ 9482.133325] legacy_get_tree+0x30/0x60 > [ 9482.133866] vfs_get_tree+0x28/0xe0 > [ 9482.134392] fc_mount+0xe/0x40 > [ 9482.134908] vfs_kern_mount.part.0+0x71/0x90 > [ 9482.135428] btrfs_mount+0x13b/0x3e0 [btrfs] > [ 9482.135942] legacy_get_tree+0x30/0x60 > [ 9482.136444] vfs_get_tree+0x28/0xe0 > [ 9482.136949] path_mount+0x2d7/0xa70 > [ 9482.137438] do_mount+0x75/0x90 > [ 9482.137923] __x64_sys_mount+0x8e/0xd0 > [ 9482.138400] do_syscall_64+0x33/0x80 > [ 9482.138873] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 9482.139346] > other info that might help us debug this: >=20 > [ 9482.140735] Possible unsafe locking scenario: >=20 > [ 9482.141594] CPU0 CPU1 > [ 9482.142011] ---- ---- > [ 9482.142411] lock(btrfs-quota-00); > [ 9482.142806] lock(&fs_info->qgroup_res= can_lock); > [ 9482.143216] lock(btrfs-quota-00); > [ 9482.143629] lock(&fs_info->qgroup_rescan_lock); > [ 9482.144056] > *** DEADLOCK *** >=20 > [ 9482.145242] 2 locks held by mount/24187: > [ 9482.145637] #0: ffffa0c8411c40e8 (&type->s_umount_key#44/1){+.+.}-{= 3:3}, at: alloc_super+0xb9/0x400 > [ 9482.146061] #1: ffffa0c892ebd3a0 (btrfs-quota-00){++++}-{3:3}, at: = __btrfs_tree_read_lock+0x27/0x120 [btrfs] > [ 9482.146509] > stack backtrace: > [ 9482.147350] CPU: 1 PID: 24187 Comm: mount Not tainted 5.10.0-rc4-btr= fs-next-73 #1 > [ 9482.147788] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), B= IOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 > [ 9482.148709] Call Trace: > [ 9482.149169] dump_stack+0x8d/0xb5 > [ 9482.149628] check_noncircular+0xff/0x110 > [ 9482.150090] check_prev_add+0x91/0xc60 > [ 9482.150561] ? kvm_clock_read+0x14/0x30 > [ 9482.151017] ? kvm_sched_clock_read+0x5/0x10 > [ 9482.151470] __lock_acquire+0x1740/0x3110 > [ 9482.151941] ? __btrfs_tree_read_lock+0x27/0x120 [btrfs] > [ 9482.152402] lock_acquire+0xd8/0x490 > [ 9482.152887] ? qgroup_rescan_init+0x43/0xf0 [btrfs] > [ 9482.153354] __mutex_lock+0xa3/0xb30 > [ 9482.153826] ? qgroup_rescan_init+0x43/0xf0 [btrfs] > [ 9482.154301] ? qgroup_rescan_init+0x43/0xf0 [btrfs] > [ 9482.154768] ? qgroup_rescan_init+0x43/0xf0 [btrfs] > [ 9482.155226] qgroup_rescan_init+0x43/0xf0 [btrfs] > [ 9482.155690] btrfs_read_qgroup_config+0x43a/0x550 [btrfs] > [ 9482.156160] open_ctree+0x1228/0x18a0 [btrfs] > [ 9482.156643] btrfs_mount_root.cold+0x13/0xed [btrfs] > [ 9482.157108] ? rcu_read_lock_sched_held+0x5d/0x90 > [ 9482.157567] ? kfree+0x31f/0x3e0 > [ 9482.158030] legacy_get_tree+0x30/0x60 > [ 9482.158489] vfs_get_tree+0x28/0xe0 > [ 9482.158947] fc_mount+0xe/0x40 > [ 9482.159403] vfs_kern_mount.part.0+0x71/0x90 > [ 9482.159875] btrfs_mount+0x13b/0x3e0 [btrfs] > [ 9482.160335] ? rcu_read_lock_sched_held+0x5d/0x90 > [ 9482.160805] ? kfree+0x31f/0x3e0 > [ 9482.161260] ? legacy_get_tree+0x30/0x60 > [ 9482.161714] legacy_get_tree+0x30/0x60 > [ 9482.162166] vfs_get_tree+0x28/0xe0 > [ 9482.162616] path_mount+0x2d7/0xa70 > [ 9482.163070] do_mount+0x75/0x90 > [ 9482.163525] __x64_sys_mount+0x8e/0xd0 > [ 9482.163986] do_syscall_64+0x33/0x80 > [ 9482.164437] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 9482.164902] RIP: 0033:0x7f51e907caaa >=20 > This happens because at btrfs_read_qgroup_config() we can call > qgroup_rescan_init() while holding a read lock on a quota btree leaf, > acquired by the previous call to btrfs_search_slot_for_read(), and > qgroup_rescan_init() acquires the mutex qgroup_rescan_lock. >=20 > A qgroup rescan worker does the opposite: it acquires the mutex > qgroup_rescan_lock, at btrfs_qgroup_rescan_worker(), and then tries to > update the qgroup status item in the quota btree through the call to > update_qgroup_status_item(). This inversion of locking order > between the qgroup_rescan_lock mutex and quota btree locks causes the > splat. >=20 > Fix this simply by releasing and freeing the path before calling > qgroup_rescan_init() at btrfs_read_qgroup_config(). >=20 > Signed-off-by: Filipe Manana Reviewed-by: Qu Wenruo Thanks, Qu > --- > fs/btrfs/qgroup.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c > index da9b313819d5..25c07ea5c8b5 100644 > --- a/fs/btrfs/qgroup.c > +++ b/fs/btrfs/qgroup.c > @@ -497,13 +497,13 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info= *fs_info) > break; > } > out: > + btrfs_free_path(path); > fs_info->qgroup_flags |=3D flags; > if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON)) > clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags); > else if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN && > ret >=3D 0) > ret =3D qgroup_rescan_init(fs_info, rescan_progress, 0); > - btrfs_free_path(path); > =20 > if (ret < 0) { > ulist_free(fs_info->qgroup_ulist); >=20 --zZwHFv8EwYZ8jqZ3WdXac6OYu0Kr6tvF0-- --DhqbbkehEJ5bq8ZfosRU7oowa4ra1jydK Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEELd9y5aWlW6idqkLhwj2R86El/qgFAl+8cyUACgkQwj2R86El /qgI5AgAmHnBOXckZ3wNrOlpooRJ+YoUy5W/T2etajOFXawge56T7HSgHs/QoAe/ HwAZJKardrh8Tsxp8E/QDjvoUWdPh2Lhnn5KaubIB65tv5Jb/AcsK3nS74VO7qMI v0zpw0OvxrbITkosa9+ZxvcPsl2aBTqszyO59VyydqorXYN1LBxjMcXcyYkecjjN 6/nYL4500geizAPRNiS9K0ALKxwqbwBviS7If0bFdFwvjsGXJWreC8+mXcsSgrh+ xdI0hTmQeursFlnnBnOqXQv/AL7vzOnolW9if80x8qJsD6kfWOl5Na1aeLRNafOg kGqBSKZ4/+JICuFt1B4IowkDJZFh8g== =Ll31 -----END PGP SIGNATURE----- --DhqbbkehEJ5bq8ZfosRU7oowa4ra1jydK--