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 <[email protected]> --- block/blk-throttle.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index b771c4299982..d52cac9f3a7c 100644 --- 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) -- 2.25.4
