From 18dc22c19bef520cca11ce4c0807ac9dec48d31f Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Thu, 20 Oct 2016 10:28:41 +0800 Subject: [PATCH] btrfs: Add WARN_ON for qgroup reserved underflow Goldwyn Rodrigues has exposed and fixed a bug which underflows btrfs qgroup reserved space, and leads to non-writable fs. This reminds us that we don't have enough underflow check for qgroup reserved space. For underflow case, we should not really underflow the numbers but warn and keeps qgroup still work. So add more check on qgroup reserved space and add WARN_ON() and btrfs_warn() for any underflow case. Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Reviewed-by: Goldwyn Rodrigues Signed-off-by: David Sterba --- fs/btrfs/qgroup.c | 31 ++++++++++++++++++++++++++----- 1 file changed, 26 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index 662821f1252c..1c555f1e49ba 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1038,6 +1038,15 @@ static void qgroup_dirty(struct btrfs_fs_info *fs_info, list_add(&qgroup->dirty, &fs_info->dirty_qgroups); } +static void report_reserved_underflow(struct btrfs_fs_info *fs_info, + struct btrfs_qgroup *qgroup, + u64 num_bytes) +{ + btrfs_warn(fs_info, + "qgroup %llu reserved space underflow, have: %llu, to free: %llu", + qgroup->qgroupid, qgroup->reserved, num_bytes); + qgroup->reserved = 0; +} /* * The easy accounting, if we are adding/removing the only ref for an extent * then this qgroup and all of the parent qgroups get their reference and @@ -1065,8 +1074,12 @@ static int __qgroup_excl_accounting(struct btrfs_fs_info *fs_info, WARN_ON(sign < 0 && qgroup->excl < num_bytes); qgroup->excl += sign * num_bytes; qgroup->excl_cmpr += sign * num_bytes; - if (sign > 0) - qgroup->reserved -= num_bytes; + if (sign > 0) { + if (WARN_ON(qgroup->reserved < num_bytes)) + report_reserved_underflow(fs_info, qgroup, num_bytes); + else + qgroup->reserved -= num_bytes; + } qgroup_dirty(fs_info, qgroup); @@ -1086,8 +1099,13 @@ static int __qgroup_excl_accounting(struct btrfs_fs_info *fs_info, qgroup->rfer_cmpr += sign * num_bytes; WARN_ON(sign < 0 && qgroup->excl < num_bytes); qgroup->excl += sign * num_bytes; - if (sign > 0) - qgroup->reserved -= num_bytes; + if (sign > 0) { + if (WARN_ON(qgroup->reserved < num_bytes)) + report_reserved_underflow(fs_info, qgroup, + num_bytes); + else + qgroup->reserved -= num_bytes; + } qgroup->excl_cmpr += sign * num_bytes; qgroup_dirty(fs_info, qgroup); @@ -2424,7 +2442,10 @@ void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info, qg = unode_aux_to_qgroup(unode); - qg->reserved -= num_bytes; + if (WARN_ON(qg->reserved < num_bytes)) + report_reserved_underflow(fs_info, qg, num_bytes); + else + qg->reserved -= num_bytes; list_for_each_entry(glist, &qg->groups, next_group) { ret = ulist_add(fs_info->qgroup_ulist, -- 2.20.1