linux-kernel - Re: [PATCH 8/8] blk-map: reimplement blk_rq_map_user() using blk_rq_map_user

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Message-ID: <49D3699F.4030105@kernel.org>
Date:	Wed, 01 Apr 2009 22:18:23 +0900
From:	Tejun Heo <tj@...nel.org>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
CC:	axboe@...nel.dk, bharrosh@...asas.com,
	linux-kernel@...r.kernel.org, tj@...el.org
Subject: Re: [PATCH 8/8] blk-map: reimplement blk_rq_map_user() using blk_rq_map_user_iov()

Tejun Heo wrote:
>>> reason blk_rq_map_user() had multiple bio chaining was to work around
>>> BIO_MAX_SIZE.  blk_rq_map_user_iov() doesn't support multiple bio
>>> chaining, so sans blk_rq_append_bio() or playing with rq/bio internals
>>> directly, there's no way to use or even know about multiple bios.
>> Yes, only non iovec interface of SG_IO supports large data
>> transfer. Users have been lived with that.
> 
> This patch doesn't remove any feature.  You don't lose anything.  What
> used to be done with multiple bios is now done with single bio.  The
> implementation is simpler and shorter.  Using or not using multiple
> bios doesn't (and shouldn't) make any difference to blk_map_*() users.

Oh.. and blk_rq_map_user_iov() now gets to play with large requests
too.  :-)

-- 
tejun
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