From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Nilay Shroff <nilay@linux.ibm.com>
Subject: Re: [PATCH 1/2] block: move queue quiesce into elevator_change()
Date: Wed, 7 May 2025 22:48:01 +0800 [thread overview]
Message-ID: <aBtyobQ2NxLjFkET@fedora> (raw)
In-Reply-To: <aBtuCDKTQK1PReDg@fedora>
On Wed, May 07, 2025 at 10:28:24PM +0800, Ming Lei wrote:
> On Wed, May 07, 2025 at 03:53:49PM +0200, Christoph Hellwig wrote:
> > On Wed, May 07, 2025 at 08:04:02PM +0800, Ming Lei wrote:
> > > blk_mq_freeze_queue() can't be called on quiesced queue, otherwise it may
> > > never return if there is any queued requests.
> > >
> > > Fix it by moving queue quiesce int elevator_change() by adding one flag to
> > > 'struct elv_change_ctx' for controlling this behavior.
> >
> > Why do we even need to quiesce the queue here, and not anywhere else?
>
> Quiesce is for draining the in-progress critical area, which can't be
> covered by queue freeze. Typically, all requests are freed, the run queue
> activity isn't finished yet, so schedule data can be touched by the un-finished
> code path.
>
> We did fix this kind of bugs by queue quiesce several times.
For example:
24f5a90f0d13 blk-mq: quiesce queue during switching io sched and updating nr_requests
c2856ae2f315 blk-mq: quiesce queue before freeing queue
Ming
next prev parent reply other threads:[~2025-05-07 14:48 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-07 12:04 [PATCH 0/2] block: fix hang in elevator_change() and improve elevator_set_none Ming Lei
2025-05-07 12:04 ` [PATCH 1/2] block: move queue quiesce into elevator_change() Ming Lei
2025-05-07 13:53 ` Christoph Hellwig
2025-05-07 14:28 ` Ming Lei
2025-05-07 14:48 ` Ming Lei [this message]
2025-05-07 19:05 ` Nilay Shroff
2025-05-08 3:02 ` Ming Lei
2025-05-08 5:03 ` Christoph Hellwig
2025-05-08 8:03 ` Ming Lei
2025-05-07 12:04 ` [PATCH 2/2] block: avoid unnecessary queue freeze in elevator_set_none() Ming Lei
2025-05-07 13:54 ` Christoph Hellwig
2025-05-08 3:57 ` Ming Lei
2025-05-08 5:04 ` Christoph Hellwig
2025-05-08 8:16 ` Ming Lei
2025-05-07 19:20 ` Nilay Shroff
2025-05-08 4:31 ` [PATCH 0/2] block: fix hang in elevator_change() and improve elevator_set_none Shinichiro Kawasaki
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