blk-throttle: don't check whether or not lower limit is valid if CONFIG_BLK_DEV_THROT...

blk_throtl_update_limit_valid() will search for descendants to see if
'LIMIT_LOW' of bps/iops and READ/WRITE is nonzero. However, they're always
zero if CONFIG_BLK_DEV_THROTTLING_LOW is not set, furthermore, a lot of
time will be wasted to iterate descendants.

Thus do nothing in blk_throtl_update_limit_valid() in such situation.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index b771c42999827c5c70f2941bd16780f67e4fc17a..d52cac9f3a7c235b7b3fcb1a574b2fb91c70bb7c 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -587,6 +587,7 @@ static void throtl_pd_online(struct blkg_policy_data *pd)
        tg_update_has_rules(tg);
 }
 
+#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
 static void blk_throtl_update_limit_valid(struct throtl_data *td)
 {
        struct cgroup_subsys_state *pos_css;
@@ -607,6 +608,11 @@ static void blk_throtl_update_limit_valid(struct throtl_data *td)
 
        td->limit_valid[LIMIT_LOW] = low_valid;
 }
+#else
+static inline void blk_throtl_update_limit_valid(struct throtl_data *td)
+{
+}
+#endif
 
 static void throtl_upgrade_state(struct throtl_data *td);
 static void throtl_pd_offline(struct blkg_policy_data *pd)