From: Ming Lei <ming.lei@xxxxxxxxxx>
commit 24f5a90f0d13a97b51aa79f468143fafea4246bb upstream
Dispatch may still be in-progress after queue is frozen, so we have to
quiesce queue before switching IO scheduler and updating nr_requests.
Also when switching io schedulers, blk_mq_run_hw_queue() may still be
called somewhere(such as from nvme_reset_work()), and io scheduler's
per-hctx data may not be setup yet, so cause oops even inside
blk_mq_hctx_has_pending(), such as it can be run just between:
ret = e->ops.mq.init_sched(q, e);
AND
ret = e->ops.mq.init_hctx(hctx, i)
inside blk_mq_init_sched().
This reverts commit 7a148c2fcff8330(block: don't call blk_mq_quiesce_queue()
after queue is frozen) basically, and makes sure blk_mq_hctx_has_pending
won't be called if queue is quiesced.
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Fixes: 7a148c2fcff83309(block: don't call blk_mq_quiesce_queue() after queue is frozen)
Reported-by: Yi Zhang <yi.zhang@xxxxxxxxxx>
Tested-by: Yi Zhang <yi.zhang@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxxx>
---
block/blk-mq.c | 27 ++++++++++++++++++++++++++-
block/elevator.c | 2 ++
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index b3f15d9c7c5a..7d396b77e5e8 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1263,7 +1263,30 @@ EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
bool blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
{
- if (blk_mq_hctx_has_pending(hctx)) {
+ int srcu_idx;
+ bool need_run;
+
+ /*
+ * When queue is quiesced, we may be switching io scheduler, or
+ * updating nr_hw_queues, or other things, and we can't run queue
+ * any more, even __blk_mq_hctx_has_pending() can't be called safely.
+ *
+ * And queue will be rerun in blk_mq_unquiesce_queue() if it is
+ * quiesced.
+ */
+ if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
+ rcu_read_lock();
+ need_run = !blk_queue_quiesced(hctx->queue) &&
+ blk_mq_hctx_has_pending(hctx);
+ rcu_read_unlock();
+ } else {
+ srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
+ need_run = !blk_queue_quiesced(hctx->queue) &&
+ blk_mq_hctx_has_pending(hctx);
+ srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
+ }
+
+ if (need_run) {
__blk_mq_delay_run_hw_queue(hctx, async, 0);
return true;
}
@@ -2710,6 +2733,7 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
return -EINVAL;
blk_mq_freeze_queue(q);
+ blk_mq_quiesce_queue(q);
ret = 0;
queue_for_each_hw_ctx(q, hctx, i) {
@@ -2734,6 +2758,7 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
if (!ret)
q->nr_requests = nr;
+ blk_mq_unquiesce_queue(q);
blk_mq_unfreeze_queue(q);
return ret;
diff --git a/block/elevator.c b/block/elevator.c
index 153926a90901..229eb4b5604c 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -951,6 +951,7 @@ static int elevator_switch_mq(struct request_queue *q,
int ret;
blk_mq_freeze_queue(q);
+ blk_mq_quiesce_queue(q);
if (q->elevator) {
if (q->elevator->registered)
@@ -977,6 +978,7 @@ static int elevator_switch_mq(struct request_queue *q,
blk_add_trace_msg(q, "elv switch: none");
out:
+ blk_mq_unquiesce_queue(q);
blk_mq_unfreeze_queue(q);
return ret;
}
--
2.7.4
