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Message-ID: <20090611110903.GO11363@kernel.dk>
Date: Thu, 11 Jun 2009 13:09:03 +0200
From: Jens Axboe <jens.axboe@...cle.com>
To: Kiyoshi Ueda <k-ueda@...jp.nec.com>
Cc: linux-kernel@...r.kernel.org,
device-mapper development <dm-devel@...hat.com>,
Boaz Harrosh <bharrosh@...asas.com>,
Jun'ichi Nomura <j-nomura@...jp.nec.com>
Subject: Re: [PATCH block#for-2.6.31] block: add request clone interface
(v2)
On Thu, Jun 11 2009, Kiyoshi Ueda wrote:
> Hi Jens,
>
> This patch adds the following 2 interfaces for request-stacking drivers:
>
> - blk_rq_prep_clone(struct request *clone, struct request *orig,
> struct bio_set *bs, gfp_t gfp_mask,
> int (*bio_ctr)(struct bio *, struct bio*, void *),
> void *data)
> * Clones bios in the original request to the clone request
> (bio_ctr is called for each cloned bios.)
> * Copies attributes of the original request to the clone request.
> The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not
> copied.
>
> - blk_rq_unprep_clone(struct request *clone)
> * Frees cloned bios from the clone request.
>
> Request stacking drivers (e.g. request-based dm) need to make a clone
> request for a submitted request and dispatch it to other devices.
>
> To allocate request for the clone, request stacking drivers may not
> be able to use blk_get_request() because the allocation may be done
> in an irq-disabled context.
> So blk_rq_prep_clone() takes a request allocated by the caller
> as an argument.
>
> For each clone bio in the clone request, request stacking drivers
> should be able to set up their own completion handler.
> So blk_rq_prep_clone() takes a callback function which is called
> for each clone bio, and a pointer for private data which is passed
> to the callback.
>
> NOTE:
> blk_rq_prep_clone() doesn't copy any actual data of the original
> request. Pages are shared between original bios and cloned bios.
> So caller must not complete the original request before the clone
> request.
This looks good to me now, I've applied it.
--
Jens Axboe
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