From: Andrzej Jakowski <andrzej.jakowski@linux.intel.com>
To: Keith Busch <kbusch@kernel.org>
Cc: axboe@kernel.dk, song@kernel.org, linux-block@vger.kernel.org,
linux-raid@vger.kernel.org,
Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Subject: Re: [PATCH v2 2/2] md: enable io polling
Date: Wed, 12 Feb 2020 14:00:10 -0700 [thread overview]
Message-ID: <e9941d4d-c403-4177-526d-b3086207f31a@linux.intel.com> (raw)
In-Reply-To: <20200211211334.GB3837@redsun51.ssa.fujisawa.hgst.com>
On 2/11/20 2:13 PM, Keith Busch wrote:
> I must be missing something: md's make_request_fn always returns
> BLK_QC_T_NONE for the cookie, and that couldn't get past blk_poll's
> blk_qc_t_valid(cookie) check. How does the initial blk_poll() caller get
> a valid cookie for an md backing device's request_queue? And how is the
> same cookie valid for more than one request_queue?
That's true md_make_request() always returns BLK_QC_T_NONE. md_make_request()
recursively calls generic_make_request() for the underlying device (e.g. nvme).
That block io request directed to member disk is added into bio_list and is
processed later by top level generic_make_request(). generic_make_request()
returns cookie that is returned by blk_mq_make_request().
That cookie is later used to poll for completion.
next prev parent reply other threads:[~2020-02-12 21:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-11 19:17 [PATCH v2 0/2] Enable polling on stackable devices Andrzej Jakowski
2020-02-11 19:17 ` [PATCH v2 1/2] block: reintroduce polling on bio level Andrzej Jakowski
2020-02-11 19:17 ` [PATCH v2 2/2] md: enable io polling Andrzej Jakowski
2020-02-11 21:13 ` Keith Busch
2020-02-12 21:00 ` Andrzej Jakowski [this message]
2020-02-12 21:42 ` Keith Busch
2020-02-13 20:19 ` Andrzej Jakowski
2020-02-14 19:25 ` Keith Busch
2020-02-21 15:25 ` Andrzej Jakowski
2020-02-21 16:34 ` Keith Busch
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