From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org,
Jeffle Xu <jefflexu@linux.alibaba.com>,
Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, linux-raid@vger.kernel.org,
Song Liu <song@kernel.org>,
linux-nvme@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
Bart Van Assche <bvanassche@acm.org>
Subject: Re: [RFC PATCH 2/2] block: support to freeze bio based request queue
Date: Thu, 15 Apr 2021 21:56:11 +0800 [thread overview]
Message-ID: <YHhF+3Qw4Y+hv5X4@T590> (raw)
In-Reply-To: <20210415103310.1513841-3-ming.lei@redhat.com>
On Thu, Apr 15, 2021 at 06:33:10PM +0800, Ming Lei wrote:
> For bio based request queue, the queue usage refcnt is only grabbed
> during submission, which isn't consistent with request base queue.
>
> Queue freezing has been used widely, and turns out it is very useful
> to quiesce queue activity.
>
> Support to freeze bio based request queue by the following approach:
>
> 1) grab two queue usage refcount for blk-mq before submitting blk-mq
> bio, one is for bio, anther is for request;
>
> 2) add bio flag of BIO_QUEUE_REFFED for making sure that only one
> refcnt is grabbed for each bio, so we can put the refcnt when the
> bio is going away
>
> 3) nvme mpath is a bit special, because same bio is used for both
> mpath queue and underlying nvme queue. So we put the mpath queue's
> usage refcnt before completing the nvme request.
RAID needs similar handling too, but it is easy to do, see md_end_io().
--
Ming
next prev parent reply other threads:[~2021-04-15 13:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-15 10:33 [RFC PATCH 0/2] block: support to freeze bio based queue Ming Lei
2021-04-15 10:33 ` [RFC PATCH 1/2] percpu_ref: add percpu_ref_tryget_many_live Ming Lei
2021-04-15 19:50 ` Bart Van Assche
2021-04-15 10:33 ` [RFC PATCH 2/2] block: support to freeze bio based request queue Ming Lei
2021-04-15 13:56 ` Ming Lei [this message]
2021-04-15 20:16 ` [dm-devel] " Bart Van Assche
2021-04-16 1:28 ` Ming Lei
2021-04-19 12:05 ` JeffleXu
2021-04-19 13:50 ` Ming Lei
2021-04-20 7:21 ` JeffleXu
2021-04-20 7:58 ` Ming Lei
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