linux-kernel - Re: [PATCH 6/6] blk-mq: remove REQ_ATOM

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Message-ID: <20171213160913.GR3919388@devbig577.frc2.facebook.com>
Date:   Wed, 13 Dec 2017 08:09:13 -0800
From:   Tejun Heo <tj@...nel.org>
To:     "jianchao.wang" <jianchao.w.wang@...cle.com>
Cc:     axboe@...nel.dk, linux-kernel@...r.kernel.org, oleg@...hat.com,
        peterz@...radead.org, kernel-team@...com, osandov@...com
Subject: Re: [PATCH 6/6] blk-mq: remove REQ_ATOM_STARTED

Hello,

On Wed, Dec 13, 2017 at 11:05:11AM +0800, jianchao.wang wrote:
> Just don't quite understand the strict definition of "generation" you said.
> A allocation->free cycle is a generation ? or a idle->in-flight cycle is a
> generation? The idle->in-flight cycle could include the requeue case as above.
> Can you clarify this?

So, a request is

* IN_FLIGHT, if it can be completed by the lower level driver

* COMPLETE, if the lower level driver indicated completion but block
  layer is still processing.

* IDLE, if neither of the above two.

and generation is bumped up on IDLE -> IN_FLIGHT to distinguish
different IN_FLIGHT instances.

Thanks.

-- 
tejun