From patchwork Wed May 20 06:58:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 11559429 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 37C6560D for ; Wed, 20 May 2020 06:59:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 204D7207D3 for ; Wed, 20 May 2020 06:59:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726522AbgETG7D (ORCPT ); Wed, 20 May 2020 02:59:03 -0400 Received: from mx2.suse.de ([195.135.220.15]:42420 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726369AbgETG7D (ORCPT ); Wed, 20 May 2020 02:59:03 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id CDA97AC77 for ; Wed, 20 May 2020 06:59:04 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH 2/2] btrfs: relocation: Clear the DEAD_RELOC_TREE bit for orphan roots to prevent runaway balance Date: Wed, 20 May 2020 14:58:51 +0800 Message-Id: <20200520065851.12689-3-wqu@suse.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200520065851.12689-1-wqu@suse.com> References: <20200520065851.12689-1-wqu@suse.com> MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org [BUG] There are several reported runaway balance, that balance is flooding the kernel with "Found X extents" where the X never changes. [CAUSE] Commit d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") introduced BTRFS_ROOT_DEAD_RELOC_TREE bit to indicate that one subvolume has finished its tree blocks swap with its reloc tree. However if balance is canceled or hits ENOSPC halfway, we didn't clear the BTRFS_ROOT_DEAD_RELOC_TREE bit, leaving that bit hanging forever until unmount. Any subvolume root with that bit, would cause backref cache to skip this tree block, as it has finished its tree block swap. This would cause all tree blocks of that root be ignored by balance, leading to runaway balance. [FIX] Fix the problem by also clearing the BTRFS_ROOT_DEAD_RELOC_TREE bit for the original subvolume of orphan reloc root. Furthermore to avoid such damn bug to bother anybody anymore, add unmount time check to detect and warn about this bit. Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") Signed-off-by: Qu Wenruo --- fs/btrfs/disk-io.c | 1 + fs/btrfs/relocation.c | 2 ++ 2 files changed, 3 insertions(+) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index fced949b150c..e6def8fc87dd 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1996,6 +1996,7 @@ void btrfs_put_root(struct btrfs_root *root) if (refcount_dec_and_test(&root->refs)) { WARN_ON(!RB_EMPTY_ROOT(&root->inode_tree)); + WARN_ON(test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state)); if (root->anon_dev) free_anon_bdev(root->anon_dev); btrfs_drew_lock_destroy(&root->snapshot_lock); diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 420348606123..595097c4a060 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -1936,6 +1936,8 @@ void merge_reloc_roots(struct reloc_control *rc) root->reloc_root = NULL; btrfs_put_root(reloc_root); } + clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, + &root->state); btrfs_put_root(root); }