From: Ming Lei ming.lei@redhat.com
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@lst.de Fixes: 7a148c2fcff83309(block: don't call blk_mq_quiesce_queue() after queue is frozen) Reported-by: Yi Zhang yi.zhang@redhat.com Tested-by: Yi Zhang yi.zhang@redhat.com Signed-off-by: Ming Lei ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Jack Wang jinpu.wang@profitbricks.com --- 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; }