From 6a132300927252101f65b7008559bb92732abc73 Mon Sep 17 00:00:00 2001 From: Baolin Wang Date: Thu, 8 Oct 2020 11:52:27 +0800 Subject: [PATCH 2107/2944] blk-throttle: Move service tree validation out of the throtl_rb_first() fix #30641350 commit 2397611ac802c4f8028b6b2e585b9857d2f8138b upstream The throtl_schedule_next_dispatch() will validate if the service queue is empty before calling update_min_dispatch_time(), and the update_min_dispatch_time() will call throtl_rb_first(), which will validate service queue again. Thus we can move the service queue validation out of the throtl_rb_first() to remove the redundant validation in the fast path. Signed-off-by: Baolin Wang Signed-off-by: Jens Axboe Reviewed-by: Joseph Qi --- block/blk-throttle.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 5db3cff..c42c771 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -685,9 +685,6 @@ static void throtl_pd_reset(struct blkg_policy_data *pd) throtl_rb_first(struct throtl_service_queue *parent_sq) { struct rb_node *n; - /* Service tree is empty */ - if (!parent_sq->nr_pending) - return NULL; n = rb_first_cached(&parent_sq->pending_tree); WARN_ON_ONCE(!n); @@ -1343,9 +1340,13 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq) unsigned int nr_disp = 0; while (1) { - struct throtl_grp *tg = throtl_rb_first(parent_sq); + struct throtl_grp *tg; struct throtl_service_queue *sq; + if (!parent_sq->nr_pending) + break; + + tg = throtl_rb_first(parent_sq); if (!tg) break; -- 1.8.3.1