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 22:28:24 +0800 [thread overview]
Message-ID: <aBtuCDKTQK1PReDg@fedora> (raw)
In-Reply-To: <20250507135349.GA1019@lst.de>
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.
Thanks,
Ming
next prev parent reply other threads:[~2025-05-07 14:28 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 [this message]
2025-05-07 14:48 ` Ming Lei
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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