From patchwork Tue Feb 26 07:06:32 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qu Wenruo X-Patchwork-Id: 10829585 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id EE8AF17EF for ; Tue, 26 Feb 2019 07:06:39 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DBEEA29BFF for ; Tue, 26 Feb 2019 07:06:39 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CD11B2B304; Tue, 26 Feb 2019 07:06:39 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 66C5829BFF for ; Tue, 26 Feb 2019 07:06:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726525AbfBZHGi (ORCPT ); Tue, 26 Feb 2019 02:06:38 -0500 Received: from mx2.suse.de ([195.135.220.15]:37038 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725940AbfBZHGh (ORCPT ); Tue, 26 Feb 2019 02:06:37 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id CB14CACBC for ; Tue, 26 Feb 2019 07:06:36 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Subject: [PATCH v2] btrfs-progs: balance: Sync the fs before balancing metadata chunks Date: Tue, 26 Feb 2019 15:06:32 +0800 Message-Id: <20190226070632.14715-1-wqu@suse.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP [BUG] Btrfs will report false ENOSPC balancing metadata chunk. The following script can easily reproduce it: #!/bin/bash dev=/dev/test/test mnt=/mnt/btrfs umount $dev &> /dev/null umount $mnt &> /dev/null mkfs.btrfs -f $dev mount $dev $mnt btrfs subv create $mnt/subv for ((i = 0; i < 1024; i++)) do xfs_io -f -c "pwrite 0 4k" $mnt/subv/file_$i > /dev/null done btrfs balance start -m $mnt [CAUSE] It's metadata space_info::bytes_may_use causing the problem. For above case, we need to reserve enough metadata space for all the created small files. [FIX] The most straightforward is to sync the fs before balancing metadata chunks. We could enhance the kernel bytes_may_use calculation, but I doubt about the complexity. So I take the easy fix to reduce the false ENOSPC reports. Signed-off-by: Qu Wenruo --- changelog: v2: - Use btrfs_util_sync_fd() to sync the fs - Add comment on why we should error out for sync failure --- cmds-balance.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/cmds-balance.c b/cmds-balance.c index 15dc385e0606..fd5355f13ef9 100644 --- a/cmds-balance.c +++ b/cmds-balance.c @@ -24,6 +24,7 @@ #include #include #include +#include #include "kerncompat.h" #include "ctree.h" @@ -32,6 +33,7 @@ #include "commands.h" #include "utils.h" +#include "utils.h" #include "help.h" static const char * const balance_cmd_group_usage[] = { @@ -455,6 +457,26 @@ static int do_balance(const char *path, struct btrfs_ioctl_balance_args *args, printf("\nStarting balance without any filters.\n"); } + /* + * There may be many over-reserved space for metadata block groups, + * especially for inlined file extents. + * + * Do a sync here will free those over-reserved space and hugely + * reduce the possibility of some false ENOSPC + */ + if (args->flags & BTRFS_BALANCE_METADATA) { + ret = btrfs_util_sync_fd(fd); + if (ret) { + /* + * Failed to sync fs is a big problem, normally caused + * by aborted transaction. + */ + error("failed to sync the fs before balance: %m"); + ret = -errno; + goto out; + } + } + ret = ioctl(fd, BTRFS_IOC_BALANCE_V2, args); if (ret < 0) { /*