Linux-NVME Archive on lore.kernel.org
 help / color / Atom feed
From: Jens Axboe <axboe@kernel.dk>
To: Sagi Grimberg <sagi@grimberg.me>,
	linux-nvme@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
	Keith Busch <kbusch@kernel.org>
Cc: linux-block@vger.kernel.org, Ming Lin <mlin@kernel.org>,
	Chao Leng <lengchao@huawei.com>
Subject: Re: [PATCH v4 1/2] blk-mq: add async quiesce interface
Date: Mon, 27 Jul 2020 16:13:31 -0600
Message-ID: <fe247bae-8428-bca8-81b5-a7015bc39591@kernel.dk> (raw)
In-Reply-To: <20200727220717.278116-2-sagi@grimberg.me>

On 7/27/20 4:07 PM, Sagi Grimberg wrote:
> Drivers that may have to quiesce a large amount of request queues at once
> (e.g. controller or adapter reset). These drivers would benefit from an
> async quiesce interface such that the can trigger quiesce asynchronously
> and wait for all in parallel.
> 
> This leaves the synchronization responsibility to the driver, but adds
> a convenient interface to quiesce async and wait in a single pass.
> 
> Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
> ---
>  block/blk-mq.c         | 46 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/blk-mq.h |  4 ++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index abcf590f6238..d913924117d2 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -209,6 +209,52 @@ void blk_mq_quiesce_queue_nowait(struct request_queue *q)
>  }
>  EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
>  
> +void blk_mq_quiesce_queue_async(struct request_queue *q)
> +{
> +	struct blk_mq_hw_ctx *hctx;
> +	unsigned int i;
> +	int rcu = false;
> +
> +	blk_mq_quiesce_queue_nowait(q);
> +
> +	queue_for_each_hw_ctx(q, hctx, i) {
> +		hctx->rcu_sync = kmalloc(sizeof(*hctx->rcu_sync), GFP_KERNEL);
> +		if (!hctx->rcu_sync) {
> +			/* fallback to serial rcu sync */
> +			if (hctx->flags & BLK_MQ_F_BLOCKING)
> +				synchronize_srcu(hctx->srcu);
> +			else
> +				rcu = true;
> +		} else {
> +			init_completion(&hctx->rcu_sync->completion);
> +			init_rcu_head(&hctx->rcu_sync->head);
> +			if (hctx->flags & BLK_MQ_F_BLOCKING)
> +				call_srcu(hctx->srcu, &hctx->rcu_sync->head,
> +					wakeme_after_rcu);
> +			else
> +				call_rcu(&hctx->rcu_sync->head,
> +					wakeme_after_rcu);
> +		}
> +	}
> +	if (rcu)
> +		synchronize_rcu();
> +}
> +EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_async);

This won't always be async, and that might matter to some users. I think
it'd be better to put the fallback path into the _wait() part instead,
since the caller should expect that to be blocking/waiting as the name
implies.

Nit picking, but...

-- 
Jens Axboe


_______________________________________________
Linux-nvme mailing list
Linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme

  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27 22:07 [PATCH v4 0/2] improve quiesce time for large amount of namespaces Sagi Grimberg
2020-07-27 22:07 ` [PATCH v4 1/2] blk-mq: add async quiesce interface Sagi Grimberg
2020-07-27 22:13   ` Jens Axboe [this message]
2020-07-27 22:37     ` Sagi Grimberg
2020-07-27 22:07 ` [PATCH v4 2/2] nvme: improve quiesce time for large amount of namespaces Sagi Grimberg

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=fe247bae-8428-bca8-81b5-a7015bc39591@kernel.dk \
    --to=axboe@kernel.dk \
    --cc=hch@lst.de \
    --cc=kbusch@kernel.org \
    --cc=lengchao@huawei.com \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-nvme@lists.infradead.org \
    --cc=mlin@kernel.org \
    --cc=sagi@grimberg.me \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-NVME Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-nvme/0 linux-nvme/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-nvme linux-nvme/ https://lore.kernel.org/linux-nvme \
		linux-nvme@lists.infradead.org
	public-inbox-index linux-nvme

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-nvme


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git