From: Joseph Qi <[email protected]>
Currently it will try to dispatch bio in throtl_upgrade_state. This may
lead to io stall in the following case.
Say the hierarchy is like:
/-test1
|-subtest1
and subtest1 has 32 queued bios now.
throtl_pending_timer_fn throtl_upgrade_state
------------------------------------------------------------------------
upgrade to max
throtl_select_dispatch
throtl_schedule_next_dispatch
throtl_select_dispatch
throtl_schedule_next_dispatch
Since throtl_select_dispatch will move queued bios from subtest1 to
test1 in throtl_upgrade_state, it will then just do nothing in
throtl_pending_timer_fn. As a result, queued bios won't be dispatched
any more if no proper timer scheduled.
Fix this issue by just scheduling dispatch now and let the dispatch be
done only in timer.
Signed-off-by: Joseph Qi <[email protected]>
---
block/blk-throttle.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 0fea76a..29d282f 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1909,13 +1909,11 @@ static void throtl_upgrade_state(struct throtl_data *td)
struct throtl_grp *tg = blkg_to_tg(blkg);
struct throtl_service_queue *sq = &tg->service_queue;
- tg->disptime = jiffies - 1;
- throtl_select_dispatch(sq);
- throtl_schedule_next_dispatch(sq, false);
+ tg->disptime = jiffies;
+ throtl_schedule_next_dispatch(sq, true);
}
rcu_read_unlock();
- throtl_select_dispatch(&td->service_queue);
- throtl_schedule_next_dispatch(&td->service_queue, false);
+ throtl_schedule_next_dispatch(&td->service_queue, true);
queue_work(kthrotld_workqueue, &td->dispatch_work);
}
--
1.9.4
