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blk-mq: quiesce queue during switching io sched and updating nr_requests 

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>
hifive-unleashed-5.1
Ming Lei 2018-01-06 16:27:38 +08:00 committed by Jens Axboe
parent c2856ae2f3
commit 24f5a90f0d
2 changed files with 28 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
block/blk-mq.c
View File

@ -1285,7 +1285,30 @@ 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) {
@ -2733,6 +2757,7 @@ 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;

2
block/elevator.c
View File

@ -968,6 +968,7 @@ 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)
@ -994,6 +995,7 @@ 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;
}