The current blk_throtl_drain() assumes that all active throtl_grps are
queued on throtl_data->service_queue, which won't be true once
hierarchy support is implemented.
This patch makes blk_throtl_drain() perform post-order walk of the
blkg hierarchy draining each associated throtl_grp, which guarantees
that all bios will eventually be pushed to the top-level service_queue
in throtl_data.
Signed-off-by: Tejun Heo <t...@kernel.org>
---
block/blk-throttle.c | 51 ++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 40 insertions(+), 11 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 8f435a7..1080563 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1299,6 +1299,28 @@ out:
return throttled;
}
+/*
+ * Dispatch all bios from all children tg's queued on @parent_sq. On
+ * return, @parent_sq is guaranteed to not have any active children tg's
+ * and all bios from previously active tg's are on @parent_sq->bio_lists[].
+ */
+static void tg_drain_bios(struct throtl_service_queue *parent_sq)
+{
+ struct throtl_grp *tg;
+
+ while ((tg = throtl_rb_first(parent_sq))) {
+ struct throtl_service_queue *sq = &tg->service_queue;
+ struct bio *bio;
+
+ throtl_dequeue_tg(tg);
+
+ while ((bio = bio_list_peek(&sq->bio_lists[READ])))
+ tg_dispatch_one_bio(tg, bio_data_dir(bio));
+ while ((bio = bio_list_peek(&sq->bio_lists[WRITE])))
+ tg_dispatch_one_bio(tg, bio_data_dir(bio));
+ }
+}
+
/**
* blk_throtl_drain - drain throttled bios
* @q: request_queue to drain throttled bios for
@@ -1309,27 +1331,34 @@ void blk_throtl_drain(struct request_queue *q)
__releases(q->queue_lock) __acquires(q->queue_lock)
{
struct throtl_data *td = q->td;
- struct throtl_service_queue *parent_sq = &td->service_queue;
- struct throtl_grp *tg;
+ struct blkcg_gq *blkg;
+ struct cgroup *pos_cgrp;
struct bio *bio;
int rw;
queue_lockdep_assert_held(q);
+ rcu_read_lock();
- while ((tg = throtl_rb_first(parent_sq))) {
- struct throtl_service_queue *sq = &tg->service_queue;
+ /*
+ * Drain each tg while doing post-order walk on the blkg tree, so
+ * that all bios are propagated to td->service_queue. It'd be
+ * better to walk service_queue tree directly but blkg walk is
+ * easier.
+ */
+ blkg_for_each_descendant_post(blkg, pos_cgrp, td->queue->root_blkg)
+ tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
- throtl_dequeue_tg(tg);
+ tg_drain_bios(&td_root_tg(td)->service_queue);
- while ((bio = bio_list_peek(&sq->bio_lists[READ])))
- tg_dispatch_one_bio(tg, bio_data_dir(bio));
- while ((bio = bio_list_peek(&sq->bio_lists[WRITE])))
- tg_dispatch_one_bio(tg, bio_data_dir(bio));
- }
+ /* finally, transfer bios from top-level tg's into the td */
+ tg_drain_bios(&td->service_queue);
+
+ rcu_read_unlock();
spin_unlock_irq(q->queue_lock);
+ /* all bios now should be in td->service_queue, issue them */
for (rw = READ; rw <= WRITE; rw++)
- while ((bio = bio_list_pop(&parent_sq->bio_lists[rw])))
+ while ((bio = bio_list_pop(&td->service_queue.bio_lists[rw])))
generic_make_request(bio);
spin_lock_irq(q->queue_lock);
--
1.8.1.4
--
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