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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 22C9DEB64DA for ; Sun, 16 Jul 2023 10:19:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229881AbjGPKTk (ORCPT ); Sun, 16 Jul 2023 06:19:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229463AbjGPKTk (ORCPT ); Sun, 16 Jul 2023 06:19:40 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF464186 for ; Sun, 16 Jul 2023 03:19:38 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 38F1060C7D for ; Sun, 16 Jul 2023 10:19:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4876FC433C7; Sun, 16 Jul 2023 10:19:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689502777; bh=cB9skSrOIDXAiccrSUEb88lnXnwIoziffcYQYLOGleE=; h=Subject:To:Cc:From:Date:From; b=SpfsbRq56VvGakHiu27OuPmbPJG6AOR7hs6pefauwhbM/sikI8dYjmGfNxvvJFaDc 3FU68fCZrHMtsBWHOqfG9J7UvldaKE8WVFhpW9qGB4Iaep1MjX9P5vnFYi9c5xUmrz jSRHTOxUU8oGLQny1ZKGsVVq1+jMeSC7rKxyb+V8= Subject: FAILED: patch "[PATCH] btrfs: fix race between quota disable and relocation" failed to apply to 6.1-stable tree To: fdmanana@suse.com Cc: From: Date: Sun, 16 Jul 2023 12:19:27 +0200 Message-ID: <2023071627-serotonin-shorts-8ca4@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 8a4a0b2a3eaf75ca8854f856ef29690c12b2f531 # git commit -s git send-email --to '' --in-reply-to '2023071627-serotonin-shorts-8ca4@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: 8a4a0b2a3eaf ("btrfs: fix race between quota disable and relocation") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 8a4a0b2a3eaf75ca8854f856ef29690c12b2f531 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Mon, 19 Jun 2023 17:21:50 +0100 Subject: [PATCH] btrfs: fix race between quota disable and relocation If we disable quotas while we have a relocation of a metadata block group that has extents belonging to the quota root, we can cause the relocation to fail with -ENOENT. This is because relocation builds backref nodes for extents of the quota root and later needs to walk the backrefs and access the quota root - however if in between a task disables quotas, it results in deleting the quota root from the root tree (with btrfs_del_root(), called from btrfs_quota_disable(). This can be sporadically triggered by test case btrfs/255 from fstests: $ ./check btrfs/255 FSTYP -- btrfs PLATFORM -- Linux/x86_64 debian0 6.4.0-rc6-btrfs-next-134+ #1 SMP PREEMPT_DYNAMIC Thu Jun 15 11:59:28 WEST 2023 MKFS_OPTIONS -- /dev/sdc MOUNT_OPTIONS -- /dev/sdc /home/fdmanana/btrfs-tests/scratch_1 btrfs/255 6s ... _check_dmesg: something found in dmesg (see /home/fdmanana/git/hub/xfstests/results//btrfs/255.dmesg) - output mismatch (see /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad) --- tests/btrfs/255.out 2023-03-02 21:47:53.876609426 +0000 +++ /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad 2023-06-16 10:20:39.267563212 +0100 @@ -1,2 +1,4 @@ QA output created by 255 +ERROR: error during balancing '/home/fdmanana/btrfs-tests/scratch_1': No such file or directory +There may be more info in syslog - try dmesg | tail Silence is golden ... (Run 'diff -u /home/fdmanana/git/hub/xfstests/tests/btrfs/255.out /home/fdmanana/git/hub/xfstests/results//btrfs/255.out.bad' to see the entire diff) Ran: btrfs/255 Failures: btrfs/255 Failed 1 of 1 tests To fix this make the quota disable operation take the cleaner mutex, as relocation of a block group also takes this mutex. This is also what we do when deleting a subvolume/snapshot, we take the cleaner mutex in the cleaner kthread (at cleaner_kthread()) and then we call btrfs_del_root() at btrfs_drop_snapshot() while under the protection of the cleaner mutex. Fixes: bed92eae26cc ("Btrfs: qgroup implementation and prototypes") CC: stable@vger.kernel.org # 5.4+ Signed-off-by: Filipe Manana Signed-off-by: David Sterba diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index f8735b31da16..da1f84a0eb29 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1232,12 +1232,23 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) int ret = 0; /* - * We need to have subvol_sem write locked, to prevent races between - * concurrent tasks trying to disable quotas, because we will unlock - * and relock qgroup_ioctl_lock across BTRFS_FS_QUOTA_ENABLED changes. + * We need to have subvol_sem write locked to prevent races with + * snapshot creation. */ lockdep_assert_held_write(&fs_info->subvol_sem); + /* + * Lock the cleaner mutex to prevent races with concurrent relocation, + * because relocation may be building backrefs for blocks of the quota + * root while we are deleting the root. This is like dropping fs roots + * of deleted snapshots/subvolumes, we need the same protection. + * + * This also prevents races between concurrent tasks trying to disable + * quotas, because we will unlock and relock qgroup_ioctl_lock across + * BTRFS_FS_QUOTA_ENABLED changes. + */ + mutex_lock(&fs_info->cleaner_mutex); + mutex_lock(&fs_info->qgroup_ioctl_lock); if (!fs_info->quota_root) goto out; @@ -1319,6 +1330,7 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info) btrfs_end_transaction(trans); else if (trans) ret = btrfs_end_transaction(trans); + mutex_unlock(&fs_info->cleaner_mutex); return ret; }