On 2017年10月25日 01:11, Edmund Nadolski wrote:
>
>
> On 10/24/2017 02:39 AM, Qu Wenruo wrote:
>> When modifying qgroup relationship, for qgroup which only owns exclusive
>> extents, we will go through quick update path.
>>
>> In quick update path, we will just adding/removing exclusive and reference
>> number.
>>
>> However we did the opposite for qgroup reservation from the very
>> beginning.
>>
>> In fact, we should also inherit the qgroup reservation space, just like
>> exclusive and reference numbers.
>>
>> Fix by using the newly introduced
>> qgroup_rsv_increase/decrease_by_qgroup() function call.
>>
>> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
>> ---
>> fs/btrfs/qgroup.c | 39 ++++++++++++++++++---------------------
>> 1 file changed, 18 insertions(+), 21 deletions(-)
>>
>> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
>> index 7b89da9589c1..ba6f60fd0e96 100644
>> --- a/fs/btrfs/qgroup.c
>> +++ b/fs/btrfs/qgroup.c
>> @@ -1069,21 +1069,24 @@ static void report_reserved_underflow(struct btrfs_fs_info *fs_info,
>> #endif
>> 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
>> - * exclusive counts adjusted.
>> + * The easy accounting, we're updating qgroup relationship whose child qgroup
>> + * only have exclusive extents.
>> + * In this case, we only need to update the rfer/excl, and inherit rsv from
>> + * child qgroup (@src)
>
> I'm not sure I understand this inheritance model. Typically a child
> will inherit from one (or more) parents, but this seems to go the
> opposite way. (Perhaps it's just terminology, but I may have missed
> something here.)
Btrfs qgroup, for exclusive qgroup, it's more like a subset.
If a exclusive qgroup belongs to a parent qgroup, then parent qgroup
should have all the exclusive extents and its reservation.
So it's still like inheritance, but it's parent inheriting things from
child.
Yeah, it's opposite, and I don't have better idea to explain this.
>
> Can these relationships form a hierarchy (i.e., grandparents,
> grandchildren, etc.)?
Yes, it's possible.
Thanks,
Qu
>
> Thanks,
> Ed
>
>
>> *
>> * Caller should hold fs_info->qgroup_lock.
>> */
>> static int __qgroup_excl_accounting(struct btrfs_fs_info *fs_info,
>> struct ulist *tmp, u64 ref_root,
>> - u64 num_bytes, int sign)
>> + struct btrfs_qgroup *src, int sign)
>> {
>> struct btrfs_qgroup *qgroup;
>> struct btrfs_qgroup_list *glist;
>> struct ulist_node *unode;
>> struct ulist_iterator uiter;
>> + u64 num_bytes = src->excl;
>> int ret = 0;
>>
>> qgroup = find_qgroup_rb(fs_info, ref_root);
>> @@ -1096,13 +1099,12 @@ 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) {
>> - trace_qgroup_update_reserve(fs_info, qgroup, -(s64)num_bytes);
>> - if (qgroup->reserved < num_bytes)
>> - report_reserved_underflow(fs_info, qgroup, num_bytes);
>> - else
>> - qgroup->reserved -= num_bytes;
>> - }
>> +
>> + /* *Inherit* qgroup rsv info from @src */
>> + if (sign > 0)
>> + qgroup_rsv_increase_by_qgroup(qgroup, src);
>> + else
>> + qgroup_rsv_decrease_by_qgroup(qgroup, src);
>>
>> qgroup_dirty(fs_info, qgroup);
>>
>> @@ -1122,15 +1124,10 @@ 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) {
>> - trace_qgroup_update_reserve(fs_info, qgroup,
>> - -(s64)num_bytes);
>> - if (qgroup->reserved < num_bytes)
>> - report_reserved_underflow(fs_info, qgroup,
>> - num_bytes);
>> - else
>> - qgroup->reserved -= num_bytes;
>> - }
>> + if (sign > 0)
>> + qgroup_rsv_increase_by_qgroup(qgroup, src);
>> + else
>> + qgroup_rsv_decrease_by_qgroup(qgroup, src);
>> qgroup->excl_cmpr += sign * num_bytes;
>> qgroup_dirty(fs_info, qgroup);
>>
>> @@ -1173,7 +1170,7 @@ static int quick_update_accounting(struct btrfs_fs_info *fs_info,
>> if (qgroup->excl == qgroup->rfer) {
>> ret = 0;
>> err = __qgroup_excl_accounting(fs_info, tmp, dst,
>> - qgroup->excl, sign);
>> + qgroup, sign);
>> if (err < 0) {
>> ret = err;
>> goto out;
>>
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