cfq-iosched:questions about cfqqs' fairness

hello everyone, i have some questions about cfq,could you give me some help?thanks! codes: cfq_service_tree_add:rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies; my questions as blew: 1,why use max_slice - cfqq_slice to dertermine offset in service tree, how the offset guarantee cfqqs' fairness

[f2fs-dev] [PATCH] f2fs:fix truncate_partial_nodes bug

depth is 3,in label 'fail',for (i = depth - 3; i >= 0; i--) can only put pages[0],pages[1] also cann't be put. notes 'depth' has been changed before first 'goto fail'(ref to statemnt depth = i + 1),so pass this modified 'depth' to trace_f2fs_truncate_p