From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:45946 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753680AbbLOC3m (ORCPT ); Mon, 14 Dec 2015 21:29:42 -0500 From: Liu Bo To: linux-btrfs@vger.kernel.org Cc: zhaolei@cn.fujitsu.com Subject: [PATCH] Btrfs: do not create empty block group if we have allocated data Date: Mon, 14 Dec 2015 18:29:32 -0800 Message-Id: <1450146572-22383-1-git-send-email-bo.li.liu@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: Now we force to create empty block group to keep data profile alive, however, in the below example, we eventually get an empty block group while we're trying to get more space for other types (metadata/system), - Before, block group "A": size=2G, used=1.2G block group "B": size=2G, used=512M - After "btrfs balance start -dusage=50 mount_point", block group "A": size=2G, used=(1.2+0.5)G block group "C": size=2G, used=0 Since there is no data in block group C, it won't be deleted automatically and we have to get the unused 2G until the next mount. Balance itself just moves data and doesn't remove data, so it's safe to not create such a empty block group if we already have data allocated in other block groups. Signed-off-by: Liu Bo --- fs/btrfs/volumes.c | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 4564522..14139c9 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3400,6 +3400,7 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info) u32 count_meta = 0; u32 count_sys = 0; int chunk_reserved = 0; + u64 bytes_used = 0; /* step one make some room on all the devices */ devices = &fs_info->fs_devices->devices; @@ -3538,7 +3539,13 @@ again: goto loop; } - if ((chunk_type & BTRFS_BLOCK_GROUP_DATA) && !chunk_reserved) { + ASSERT(fs_info->data_sinfo); + spin_lock(&fs_info->data_sinfo->lock); + bytes_used = fs_info->data_sinfo->bytes_used; + spin_unlock(&fs_info->data_sinfo->lock); + + if ((chunk_type & BTRFS_BLOCK_GROUP_DATA) && + !chunk_reserved && !bytes_used) { trans = btrfs_start_transaction(chunk_root, 0); if (IS_ERR(trans)) { mutex_unlock(&fs_info->delete_unused_bgs_mutex); -- 1.7.1