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=-8.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 C94D3C433DF for ; Thu, 9 Jul 2020 10:46:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 96F93206DF for ; Thu, 9 Jul 2020 10:46:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=gmx.net header.i=@gmx.net header.b="WiwT5NiG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726408AbgGIKqw (ORCPT ); Thu, 9 Jul 2020 06:46:52 -0400 Received: from mout.gmx.net ([212.227.15.18]:41359 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726302AbgGIKqw (ORCPT ); Thu, 9 Jul 2020 06:46:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1594291607; bh=MeEB7kTZ890sEcXOYhoEh67aEsM42Bo4SCLt40m43k8=; h=X-UI-Sender-Class:Subject:To:References:From:Date:In-Reply-To; b=WiwT5NiGz57abwRFAzttuM7CwzGhVE/gKvtyAJVv9Efkq/s0TEyz9zT3ph2IEW0zQ uJd4iC0zQR1A8aXnt4GLPsO9wGUCPsCUYBN2SitIk2agvH5xvwK0e/xHA9E+krBH2U JX6f1NV5whufcB6EIUs0OB+ul7Vn+GtvNe1+tC4U= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from [0.0.0.0] ([149.28.201.231]) by mail.gmx.com (mrgmx005 [212.227.17.184]) with ESMTPSA (Nemesis) id 1McY8d-1kTvDv2DID-00curX; Thu, 09 Jul 2020 12:46:47 +0200 Subject: Re: [PATCH v2 2/2] btrfs: relocation: review the call sites which can be interruped by signal To: dsterba@suse.cz, Qu Wenruo , linux-btrfs@vger.kernel.org References: <20200709083333.137927-1-wqu@suse.com> <20200709083333.137927-2-wqu@suse.com> <20200709095413.GF28832@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 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: <93ef60a9-1365-28f7-629d-1f59e89925d6@gmx.com> Date: Thu, 9 Jul 2020 18:46:43 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200709095413.GF28832@twin.jikos.cz> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="pgPT0Mg101M40cPI3y7QDRcPxWobiqCmi" X-Provags-ID: V03:K1:5UOsQkErjSMalON7wozz2J1gpT58+FyI+TrN3sAIAAl/DqQttKy idtJPE4NMqGbR1zotyotoF6XxTo7VULx/WjvO+V4m1Ngyhhr712ODoxcGlCwgEg+MooNTnh 2pS49YAb56/EScjzHZpX5icgyP+01IgcchzdX14OfG5PwtxRCrHhSRvAINQpjQjLbQQVB53 T1JgV8ZjWB/YoOEI/Ov8Q== X-UI-Out-Filterresults: notjunk:1;V03:K0:Ba8QZN7vAoM=:2aw7IK55s1XPWx+KSrOC8S qenCe+wtty4d3wBnGohoHHy/1OdcruaFSKjd7xPJzgCnBcf+GcpjMn0rvrNTR6Umds4tgGwvl jppNDa3+0ctpF8vgi2zROsVtotBmRhtbFMsardyZQcHUQ2CVtmClonRJYPvIHyfzSw9VXI6Xl w2OO/GoiQROiZbtlAu9P4LD43eE9potnUioO3whbeqNcgOwt2Td/H/nUD7YpKHbKXamrBJSvU URizX/x/pwV+jsWp3xhkATkhnEJl11KX9eTPkgyu/OVOQ1URG33BTp+/tHOv+dccsMkiN73Bk 4JGJNvBf0WMUEJr3su590I9tZowRCPVh2eDGEsT4smtxDb2NtHnkgurDfXQhsXE/mM4SvFgP/ xgUY9ki7AsgefPkMce5GeAUTc8iek3qKJWwaY/icnHIuncVwBfAyPRXOO1kwmz+ZCN3qsk7fB UxUgfN6BjTbN6G0nKfihnB6tiAmzdprsP4wfNYZkcCJ+Puuk8Wi0/kcqz8ZEd6ID1EnrJxJZx 7tAxiKHZMRqkIZOebZR5ctrnDBTHjMqsWILxmPywAA9e7HQE2HjmDCkovoJoug+RhXpM8606a 7Gb1g0FAPCOV/WDVWiNl2vuEAfdf+ONowWYUxuyTKClycG2vqkh7rAJ3Q5VgZR+fQ//jtjUPh KOlztR9cc83M9hrlZZ+OU0rdFqbDduZgFMV2Cd0/ys5bY9KFeg0/0wM2qAXfkCXIpb+c5HT1r CFkStBgyKZq6Ug5HoUZv9BUU4tarHbN0lZIKRbNGb0aXrE8uAhpsS7NleR4ccf+c0VrEdCGK5 l0DxSWowG0SI1csMZHkjRXlAPXwBjg1n+jUMrOTPlCFmStxbyqYyiwA1LzygYAZhcYACHg3BE oUM0WSgLeYc1U28uiNybk0l/HkJnhUwwL0ulNqbXnMBhY1v8f9ONL7kvbDF1+VmVmxai68AR5 XuxOZlT1g5t7O4+6aEGtKgtpOrvsb+2nhtxUdNnyDIz+TrRYPU3UfZlus6QNxCrS/h5FVJojw SdgPxkO4J+sJSYNg/5HtbNGZevgx0EK0fxb+W3ajAMRd7x7iWH3vPiV0oPl5Y+XOay3Fej0RI xdTlZqMP/ab8hPm2h2FjdOGqF4QiXQT0LqHgQlcTpA4CXG/WJX1kgpItvaOOEdP869mAczhwI 7Z2XU0L++FwoigqWkIEadQpZatriIWHqeJzZhkmV4ZwKgSxCpCKugEliMb5LJ/N/LqkF9b9iH X7WBqQuFuAA+5D3zO4TcBfEi+xI1L+R0b23mKBA== 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) --pgPT0Mg101M40cPI3y7QDRcPxWobiqCmi Content-Type: multipart/mixed; boundary="3V3Qyx969TxDiafa3HNQXI3VQVCTsDpTi" --3V3Qyx969TxDiafa3HNQXI3VQVCTsDpTi Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 2020/7/9 =E4=B8=8B=E5=8D=885:54, David Sterba wrote: > On Thu, Jul 09, 2020 at 04:33:33PM +0800, Qu Wenruo wrote: >> Since most metadata reservation calls can return -EINTR when get >> interruped by fatal signal, we need to review the all the metadata >> reservation call sites. >> >> In relocation code, the metadata reservation happens in the following >> sites: >> - btrfs_block_rsv_refill() in merge_reloc_root() >> merge_reloc_root() is a pretty critial section, we don't want get >> interrupted by signal, so change the flush status to >> BTRFS_RESERVE_FLUSH_LIMIT, so it won't get interrupted by signal. >> Since such change can be ENPSPC-prone, also shrink the amount of >> metadata to reserve a little to avoid deadly ENOSPC there. >> >> - btrfs_block_rsv_refill() in reserve_metadata_space() >> It calls with BTRFS_RESERVE_FLUSH_LIMIT, which won't get interrupred= >> by signal. >=20 > This semantics of BTRFS_RESERVE_FLUSH_LIMIT regarding signals should be= > documented, right now there's a comment but says something about avoidi= g > deadlocks. For this, I tend to add one or more patches to add some comment for all FLUSH enums, and all their callers. I hate when some infrastructure hit me by surprise, and since ticketing system is hidden from a lot of functions, we also need to mention that -EINTR case. Thanks, Qu >=20 >> - btrfs_block_rsv_refill() in prepare_to_relocate() >> - btrfs_block_rsv_add() in prepare_to_relocate() >> - btrfs_block_rsv_refill() in relocate_block_group() >> - btrfs_delalloc_reserve_metadata() in relocate_file_extent_cluster() >> - btrfs_start_transaction() in relocate_block_group() >> - btrfs_start_transaction() in create_reloc_inode() >> Can be interruped by fatal signal and we can handle it easily. >> For these call sites, just catch the -EINTR value in btrfs_balance()= >> and count them as canceled. >> >> Signed-off-by: Qu Wenruo >> --- >> fs/btrfs/relocation.c | 13 +++++++++++-- >> fs/btrfs/volumes.c | 2 +- >> 2 files changed, 12 insertions(+), 3 deletions(-) >> >> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c >> index 2b869fb2e62c..23914edd4710 100644 >> --- a/fs/btrfs/relocation.c >> +++ b/fs/btrfs/relocation.c >> @@ -1686,12 +1686,21 @@ static noinline_for_stack int merge_reloc_root= (struct reloc_control *rc, >> btrfs_unlock_up_safe(path, 0); >> } >> =20 >> - min_reserved =3D fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2; >> + /* >> + * In merge_reloc_root(), we modify the upper level pointer to swap >> + * the tree blocks between reloc tree and subvolume tree. >> + * Thus for tree block COW, we COW at most from level 1 to root leve= l >> + * for each tree. >> + * >> + * Thus the needed metadata space is at most root_level * nodesize, >> + * and * 2 since we have two trees to COW. >> + */ >> + min_reserved =3D fs_info->nodesize * btrfs_root_level(root_item) * 2= ; >> memset(&next_key, 0, sizeof(next_key)); >> =20 >> while (1) { >> ret =3D btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved, >> - BTRFS_RESERVE_FLUSH_ALL); >> + BTRFS_RESERVE_FLUSH_LIMIT); >> if (ret) { >> err =3D ret; >> goto out; >> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c >> index aabc6c922e04..d60df30bdc47 100644 >> --- a/fs/btrfs/volumes.c >> +++ b/fs/btrfs/volumes.c >> @@ -4135,7 +4135,7 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,= >> mutex_lock(&fs_info->balance_mutex); >> if (ret =3D=3D -ECANCELED && atomic_read(&fs_info->balance_pause_req= )) >> btrfs_info(fs_info, "balance: paused"); >> - else if (ret =3D=3D -ECANCELED && atomic_read(&fs_info->balance_canc= el_req)) >> + else if (ret =3D=3D -ECANCELED || ret =3D=3D -EINTR) >=20 > Why do you remove atomic_read(&fs_info->balance_cancel_req) ? >=20 >> btrfs_info(fs_info, "balance: canceled"); >=20 > I'm not sure if it would be useful to print the reason, like >=20 > - 'canceled: user request' > - 'canceled: interrupted' >=20 >> else >> btrfs_info(fs_info, "balance: ended with status: %d", ret); >> --=20 >> 2.27.0 --3V3Qyx969TxDiafa3HNQXI3VQVCTsDpTi-- --pgPT0Mg101M40cPI3y7QDRcPxWobiqCmi Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEELd9y5aWlW6idqkLhwj2R86El/qgFAl8G9ZMACgkQwj2R86El /qjhPgf9Hp+qw58b22qqAV4lkTXTN1+oxjrApSYVMXGwpPiORzOc2td1BE84L1fk DWSx9cUkIK8GHM7KaUd82/BtY9+birl4SPJbXj5wY944LaEwdJFqzJuh+ny3Rxj5 aHV6kWUwDqpIjlhk5hOI5NHITjFWlWrbsk0HoH4KNaBa0ZRR4w/Wn43XQ8Th9HyR vN01LwQtIBcfjkUipfYu/IsfTlAgG1YOfP3NSqSR/VU8AHlnfuJfoaCw8rI2IyJS xTbkt+EtipWlEJzO3gm+O955a5ArsDYUjsW6wRRxPvPYD3PIgrAxwp8NXiX+Mru9 QC0PBQI+urRzEdMRPRZgf8SAhgrSHw== =hb8c -----END PGP SIGNATURE----- --pgPT0Mg101M40cPI3y7QDRcPxWobiqCmi--