btrfs: quota: Update quota tree after qgroup relationship change.

Previous patch modified the in memory struct but it's not written in
quota tree until next commit.
So user will still get old data using "btrfs qgroup show" after
assign/remove.

This patch will call btrfs_run_qgroups in assign ioctl so it will be
updated to in memory quota trees and user will get up-to-date results.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e38b645..ca5d968f 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4641,6 +4641,11 @@
 						sa->src, sa->dst);
 	}
 
+	/* update qgroup status and info */
+	err = btrfs_run_qgroups(trans, root->fs_info);
+	if (err < 0)
+		btrfs_error(root->fs_info, ret,
+			    "failed to update qgroup status and info\n");
 	err = btrfs_end_transaction(trans, root);
 	if (err && !ret)
 		ret = err;