btrfs: qgroup: update all parent qgroups when doing quick inherit

[BUG]
There is a bug that if a subvolume has multi-level parent qgroups, and
is able to do a quick inherit, only the direct parent qgroup got
updated:

mkfs.btrfs -f -O quota $dev
mount $dev $mnt
btrfs subv create $mnt/subv1
btrfs qgroup create 1/100 $mnt
btrfs qgroup create 2/100 $mnt
btrfs qgroup assign 1/100 2/100 $mnt
btrfs qgroup assign 0/256 1/100 $mnt
btrfs qgroup show -p --sync $mnt

Qgroupid Referenced Exclusive Parent Path
-------- ---------- --------- ------ ----
0/5 16.00KiB 16.00KiB - <toplevel>
0/256 16.00KiB 16.00KiB 1/100 subv1
1/100 16.00KiB 16.00KiB 2/100 2/100<1 member qgroup>
2/100 16.00KiB 16.00KiB - <0 member qgroups>

btrfs subv snap -i 1/100 $mnt/subv1 $mnt/snap1
btrfs qgroup show -p --sync $mnt

Qgroupid Referenced Exclusive Parent Path
-------- ---------- --------- ------ ----
0/5 16.00KiB 16.00KiB - <toplevel>
0/256 16.00KiB 16.00KiB 1/100 subv1
0/257 16.00KiB 16.00KiB 1/100 snap1
1/100 32.00KiB 32.00KiB 2/100 2/100<1 member qgroup>
2/100 16.00KiB 16.00KiB - <0 member qgroups>
# Note that 2/100 is not updated, and qgroup numbers are inconsistent

umount $mnt

[CAUSE]
If the snapshot source subvolume belongs to a parent qgroup, and the new
snapshot target is also added to the new same parent qgroup, we allow a
quick update without marking qgroup inconsistent.

But that quick update only update the parent qgroup, without checking if
there is any more parent qgroups.

[FIX]
Iterate through all parent qgroups during the quick inherit.

Reported-by: Boris Burkov <[e-mail]>
Fixes: b20fe56cd285 ("btrfs: qgroup: allow quick inherit if snapshot is created and added to the same parent")
Reviewed-by: Boris Burkov <[e-mail]>
Signed-off-by: Qu Wenruo <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/qgroup.c

···
 {
 	struct btrfs_qgroup *src;
 	struct btrfs_qgroup *parent;
+	struct btrfs_qgroup *qgroup;
 	struct btrfs_qgroup_list *list;
+	LIST_HEAD(qgroup_list);
+	const u32 nodesize = fs_info->nodesize;
 	int nr_parents = 0;
 
 	if (btrfs_qgroup_mode(fs_info) != BTRFS_QGROUP_MODE_FULL)
···
 	if (parent->excl != parent->rfer)
 		return 1;
 
-	parent->excl += fs_info->nodesize;
-	parent->rfer += fs_info->nodesize;
+	qgroup_iterator_add(&qgroup_list, parent);
+	list_for_each_entry(qgroup, &qgroup_list, iterator) {
+		qgroup->rfer += nodesize;
+		qgroup->rfer_cmpr += nodesize;
+		qgroup->excl += nodesize;
+		qgroup->excl_cmpr += nodesize;
+		qgroup_dirty(fs_info, qgroup);
+
+		/* Append parent qgroups to @qgroup_list. */
+		list_for_each_entry(list, &qgroup->groups, next_group)
+			qgroup_iterator_add(&qgroup_list, list->group);
+	}
+	qgroup_iterator_clean(&qgroup_list);
 	return 0;
 }