From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: [patchset 0/4] osd: Stop usage of blk_rq_append_bio
Date: Sat, 09 May 2009 17:12:58 +0900
Message-ID: <4A053B0A.9010501@kernel.org>
References: <4A0307F4.50205@panasas.com>
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To: Boaz Harrosh <bharrosh@panasas.com>
Cc: Jens Axboe <Jens.Axboe@oracle.com>, James Bottomley <James.Bottomley@hansenpartnership.com>, FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>, Jeff Garzik <jeff@garzik.org>, linux-scsi <linux-scsi@vger.kernel.org>, open-osd mailing-list <osd-dev@open-osd.org>, "Nicholas A. Bellinger" <nab@linux-iscsi.org>

Boaz Harrosh wrote:
> Osd library needs to submit pre-allocated bios, form several sources.
> osdblk exofs and pNFS-layout driver all have prepared bios for IO submission.
> On top of that the osd library needs to append additional segments to the
> IO memory, for get/set attributes and more.
> 
> All these are done today by use of a temporary hack - blk_rq_append_bio.
> This is bad on few accounts.
> 1. blk_rq_append_bio was not meant to be exported and is very specific to its users.
> 2. blk_rq_append_bio does not support chained bios.
> 3. blk_rq_append_bio does not bounce the bio and therefore current osd implementation
>    has a bug.
> 
> The proposed solution adds two new fixtures to the block layer, and a corresponding
> fixing patch to osd. These are:
> 
> [PATCH 1/4] allow blk_rq_map_kern to append to requests

blk_rq_map_kern() part of modification looks good to me.

Thanks.

-- 
tejun