block, bfq: invoke flush_idle_tree after reparent_active_queues in pd_offline (4d38a87f) · Commits · 戴 / test

In bfq_pd_offline(), the function bfq_flush_idle_tree() is invoked to flush the rb tree that contains all idle entities belonging to the pd (cgroup) being destroyed. In particular, bfq_flush_idle_tree() is invoked before bfq_reparent_active_queues(). Yet the latter may happen to add some entities to the idle tree. It happens if, in some of the calls to bfq_bfqq_move() performed by bfq_reparent_active_queues(), the queue to move is empty and gets expired. This commit simply reverses the invocation order between bfq_flush_idle_tree() and bfq_reparent_active_queues(). Tested-by:

<cki-project@redhat.com> Signed-off-by:

Paolo Valente <paolo.valente@linaro.org> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/bfq-cgroup.c

+13 −7

Original line number	Diff line number	Diff line
		@@ -893,13 +893,6 @@ static void bfq_pd_offline(struct blkg_policy_data *pd)
		for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) {
		st = bfqg->sched_data.service_tree + i;

		/*
		* The idle tree may still contain bfq_queues belonging
		* to exited task because they never migrated to a different
		* cgroup from the one being destroyed now.
		*/
		bfq_flush_idle_tree(st);

		/*
		* It may happen that some queues are still active
		* (busy) upon group destruction (if the corresponding
		@@ -913,6 +906,19 @@ static void bfq_pd_offline(struct blkg_policy_data *pd)
		* scheduler has taken no reference.
		*/
		bfq_reparent_active_queues(bfqd, bfqg, st, i);

		/*
		* The idle tree may still contain bfq_queues
		* belonging to exited task because they never
		* migrated to a different cgroup from the one being
		* destroyed now. In addition, even
		* bfq_reparent_active_queues() may happen to add some
		* entities to the idle tree. It happens if, in some
		* of the calls to bfq_bfqq_move() performed by
		* bfq_reparent_active_queues(), the queue to move is
		* empty and gets expired.
		*/
		bfq_flush_idle_tree(st);
		}

		__bfq_deactivate_entity(entity, false);

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