From cf25ce518e8ef9d59b292e51193bed2b023a32da Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Mon, 14 Dec 2015 18:29:32 -0800 Subject: [PATCH] Btrfs: do not create empty block group if we have allocated data 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 Signed-off-by: David Sterba --- fs/btrfs/volumes.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index bd0f45f..745a619 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3402,6 +3402,7 @@ 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; @@ -3540,7 +3541,13 @@ 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); -- 2.7.4