From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
Tejun Heo <tj@kernel.org>,
linux-block@vger.kernel.org,
"Darrick J . Wong" <djwong@kernel.org>
Subject: Re: [PATCH 4/5] block: drain file system I/O on del_gendisk
Date: Fri, 1 Oct 2021 06:13:48 +0200 [thread overview]
Message-ID: <20211001041348.GA17306@lst.de> (raw)
In-Reply-To: <YVQg/a6GnELfPV1S@T590>
On Wed, Sep 29, 2021 at 04:17:01PM +0800, Ming Lei wrote:
[full quote deleted]
> Draining request won't fix the problem completely:
>
> 1) blk-mq dispatch code may still be in-progress after q_usage_counter
> becomes zero, see the story in 662156641bc4 ("block: don't drain in-progress dispatch in
> blk_cleanup_queue()")
That commit does not have a good explanation on what it actually fixed.
> 2) elevator code / blkcg code may still be called after blk_cleanup_queue(), such
> as kyber, trace_kyber_latency()(q->disk is referred) is called in kyber's timer
> handler, and the timer is deleted via del_timer_sync() via kyber_exit_sched()
> from blk_release_queue().
Yes. There's two things we can do here:
- stop using the dev_t in tracing a request_queue
- exit the I/O schedules in del_gendisk, because they are only used
for file system I/O that requires the gendisk anyway
we'll probably want both eventually.
>
> > +
> > + rq_qos_exit(q);
> > + blk_sync_queue(q);
> > + blk_flush_integrity();
> > + /*
> > + * Allow using passthrough request again after the queue is torn down.
> > + */
> > + blk_mq_unfreeze_queue(q);
>
> Again, one FS bio is still possible to enter queue now: submit_bio_checks()
> is done before set_capacity(0), and submitted after blk_mq_unfreeze_queue()
> returns.
Not with the new patch 1 in this series.
Jens - can you take a look at the series that fixes the crashes people
are sending while I'm looking at the rest of the corner cases?
next prev parent reply other threads:[~2021-10-01 4:13 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-29 7:12 tear down file system I/O in del_gendisk v3 Christoph Hellwig
2021-09-29 7:12 ` [PATCH 1/5] block: call submit_bio_checks under q_usage_counter Christoph Hellwig
2021-10-17 1:14 ` Jens Axboe
2021-09-29 7:12 ` [PATCH 2/5] block: factor out a blk_try_enter_queue helper Christoph Hellwig
2021-09-29 7:12 ` [PATCH 3/5] block: split bio_queue_enter from blk_queue_enter Christoph Hellwig
2021-09-29 7:12 ` [PATCH 4/5] block: drain file system I/O on del_gendisk Christoph Hellwig
2021-09-29 8:17 ` Ming Lei
2021-10-01 4:13 ` Christoph Hellwig [this message]
2021-10-05 2:15 ` Ming Lei
2021-09-29 7:12 ` [PATCH 5/5] block: keep q_usage_counter in atomic mode after del_gendisk Christoph Hellwig
2021-10-12 9:33 ` [PATCH 6/5] kyber: avoid q->disk dereferences in trace points Christoph Hellwig
2021-10-14 12:57 ` Ming Lei
2021-10-14 9:23 ` tear down file system I/O in del_gendisk v3 Yi Zhang
2021-10-17 1:14 ` Jens Axboe
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