On 09/29/2016 08:15 PM, Qu Wenruo wrote:
> While the reason why qgroup reserved space may underflow is still under
> investigation, such WARN_ON will help us to expose the bug more easily,
> and for end-user we can detect and avoid underflow.
>
> Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
Looks good.
Reviewed-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> fs/btrfs/qgroup.c | 21 ++++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index 8db2e29..8532587 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -1061,8 +1061,12 @@ 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))
> + qgroup->reserved = 0;
> + else
> + qgroup->reserved -= num_bytes;
> + }
>
> qgroup_dirty(fs_info, qgroup);
>
> @@ -1082,8 +1086,12 @@ 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))
> + qgroup->reserved = 0;
> + else
> + qgroup->reserved -= num_bytes;
> + }
> qgroup->excl_cmpr += sign * num_bytes;
> qgroup_dirty(fs_info, qgroup);
>
> @@ -2201,7 +2209,10 @@ void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info,
>
> qg = u64_to_ptr(unode->aux);
>
> - qg->reserved -= num_bytes;
> + if (WARN_ON(qgroup->reserved < num_bytes))
> + qgroup->reserved = 0;
> + else
> + qgroup->reserved -= num_bytes;
>
> list_for_each_entry(glist, &qg->groups, next_group) {
> ret = ulist_add(fs_info->qgroup_ulist,
>
--
Goldwyn
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