From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-nvme@lists.infradead.org
Subject: Re: sorting out the freeze / quiesce mess
Date: Wed, 10 Nov 2021 17:52:13 +0800 [thread overview]
Message-ID: <YYuWTefkvpy5uYgs@T590> (raw)
In-Reply-To: <YYuQ9mhHtDNDVFQ3@T590>
On Wed, Nov 10, 2021 at 05:29:26PM +0800, Ming Lei wrote:
> On Wed, Nov 10, 2021 at 10:14:07AM +0100, Christoph Hellwig wrote:
> > Hi Jens and Ming,
> >
> > I've been looking into properly supporting queue freezing for bio based
> > drivers (that is only release q_usage_counter on bio completion for them).
> > And the deeper I look into the code the more I'm confused by us having
> > the blk_mq_quiesce* interface in addition to blk_freeze_queue. What
> > is a good reason to do a quiesce separately from a freeze?
>
> freeze can make sure that all requests are done, quiesce can make sure that
> dispatch critical area(covered by hctx lock/unlock) is done.
Another difference: quiesce usually is used to stop to queue requests to
LLD, and driver needs no requets queued any more after the interface returns,
freeze can't do that.
Thanks,
Ming
next prev parent reply other threads:[~2021-11-10 9:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-10 9:14 sorting out the freeze / quiesce mess Christoph Hellwig
2021-11-10 9:29 ` Ming Lei
2021-11-10 9:52 ` Ming Lei [this message]
2021-11-10 12:58 ` Christoph Hellwig
2021-11-10 14:56 ` Ming Lei
2021-11-10 10:22 ` Hannes Reinecke
2021-11-10 10:45 ` Ming Lei
2021-11-10 12:32 ` James Bottomley
2021-11-10 13:30 ` Max Gurtovoy
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