linux-kernel - Re: [PATCH] storvsc: get rid of homegrown copy_{to,from}_bounce

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Date:	Wed, 23 Sep 2015 13:32:58 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	devel@...uxdriverproject.org,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"James E.J. Bottomley" <JBottomley@...n.com>,
	Radim Kr??m???? <rkrcmar@...hat.com>
Subject: Re: [PATCH] storvsc: get rid of homegrown copy_{to,from}_bounce_buffer()

Christoph Hellwig <hch@...radead.org> writes:

> On Tue, Sep 22, 2015 at 06:27:50PM +0200, Vitaly Kuznetsov wrote:
>> Storvsc driver needs to ensure there are no 'holes' in the presented
>> sg list (all segments in the middle of the list need to be of PAGE_SIZE).
>
> I think it should instead set a virt_boundary.  That's what we added for
> the NVMe driver which has the same requirements, and Sagi recently also
> switched iSER to it after we ensured that flag is handled correctly by
> the SG_IO ioctl.

Wow,

I checked and blk_queue_virt_boundary(sdevice->request_queue, PAGE_SIZE
- 1) seems to be solving the issue completely, no bounce buffer
required. I'll test more and send v2 with removing the rest.

-- 
  Vitaly
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