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From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <tom.leiming@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Matias Bjorling <m@bjorling.me>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux SCSI List <linux-scsi@vger.kernel.org>
Subject: Re: [PATCH 5/7] blk-mq: initialize request on allocation
Date: Thu, 17 Apr 2014 16:57:05 +0200	[thread overview]
Message-ID: <20140417145705.GA14787@lst.de> (raw)
In-Reply-To: <CACVXFVMAq0qw5vXqShmhcTTA5nww_OYaVz-yiEaf3_Q3-nrJfQ@mail.gmail.com>

On Thu, Apr 17, 2014 at 10:54:23PM +0800, Ming Lei wrote:
> On Mon, Apr 14, 2014 at 4:30 PM, Christoph Hellwig <hch@lst.de> wrote:
> > If we want to share tag and request allocation between queues we cannot
> > initialize the request at init/free time, but need to initialize it
> > at allocation time as it might get used for different queues over its
> > lifetime.
> 
> Could you explain the use pattern? Looks you mean there are
> still users of the tag/req even after it is freed, that looks a bit
> weird since the tag/req can still be reallocated in another path
> after it is freed.

No difference in use pattern.  But blk_rq_init initializes the rq->q field,
and a request might get reused for a different queue.

  reply	other threads:[~2014-04-17 14:57 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <blk-mq updates>
2014-04-14  8:30 ` Christoph Hellwig
2014-04-14  8:30   ` [PATCH 1/7] blk-mq: initialize resid_len Christoph Hellwig
2014-04-14  8:30   ` [PATCH 2/7] blk-mq: do not initialize req->special Christoph Hellwig
2014-04-14  8:30   ` [PATCH 3/7] blk-mq: make ->flush_rq fully transparent to drivers Christoph Hellwig
2014-04-14  8:30   ` [PATCH 4/7] blk-mq: add ->init_request and ->exit_request methods Christoph Hellwig
2014-04-14  8:30   ` [PATCH 5/7] blk-mq: initialize request on allocation Christoph Hellwig
2014-04-17 14:54     ` Ming Lei
2014-04-17 14:57       ` Christoph Hellwig [this message]
2014-04-17 15:07         ` Ming Lei
2014-04-14  8:30   ` [PATCH 6/7] blk-mq: split out tag initialization, support shared tags Christoph Hellwig
2014-04-14  8:30   ` [PATCH 7/7] block: all blk-mq requests are tagged Christoph Hellwig
2014-04-15 20:16   ` Jens Axboe

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