block: BFQ: Add several invariant checks

If anything goes wrong with the counters that track the number of
requests, I/O locks up. Make such scenarios easier to debug by adding
invariant checks for the request counters. Additionally, check that
BFQ queues are empty before these are freed.

Cc: Jan Kara <jack@suse.cz>
Cc: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230516223853.1385255-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 3164e31..c5727af 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5403,6 +5403,9 @@ void bfq_put_queue(struct bfq_queue *bfqq)
        if (bfqq->bfqd->last_completed_rq_bfqq == bfqq)
                bfqq->bfqd->last_completed_rq_bfqq = NULL;
 
+       WARN_ON_ONCE(!list_empty(&bfqq->fifo));
+       WARN_ON_ONCE(!RB_EMPTY_ROOT(&bfqq->sort_list));
+
        kmem_cache_free(bfq_pool, bfqq);
        bfqg_and_blkg_put(bfqg);
 }
@@ -7135,6 +7138,7 @@ static void bfq_exit_queue(struct elevator_queue *e)
 {
        struct bfq_data *bfqd = e->elevator_data;
        struct bfq_queue *bfqq, *n;
+       unsigned int actuator;
 
        hrtimer_cancel(&bfqd->idle_slice_timer);
 
@@ -7143,6 +7147,11 @@ static void bfq_exit_queue(struct elevator_queue *e)
                bfq_deactivate_bfqq(bfqd, bfqq, false, false);
        spin_unlock_irq(&bfqd->lock);
 
+       for (actuator = 0; actuator < bfqd->num_actuators; actuator++)
+               WARN_ON_ONCE(bfqd->rq_in_driver[actuator]);
+       WARN_ON_ONCE(bfqd->tot_rq_in_driver);
+       WARN_ON_ONCE(bfqq->dispatched);
+
        hrtimer_cancel(&bfqd->idle_slice_timer);
 
        /* release oom-queue reference to root group */