On 24.10.2017 11:39, 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.
I'm afraid this sentence doesn't give much information about what's
really going on.
>
> 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 <w...@suse.com>
> ---
> 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)
> *
> * 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);
I'm a bit confused by the semantics of the 'sign' variable. So what you
are doing is that if sign is > 0 then you are "adding a relationship"
i.e. adding 'src reservation to 'qgroup', presumably because the src is
a child of qgroup? So you are handling both adding and deletion in the
if statement?
However, before that apparently only deleting a relation ship was
handled by that same if (And I believe that was wrong since if sign > 0
then we should be adding bytes but here we are subtracting). SO the bug
being fixed by this commit are actually 2 bugs:
1. Completely missing the "adding a relation ship case"
2. Incorrect hanlding of sign < 0, since this was handled by the sign >
0 case?
>
> 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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