linux-kernel - RE: [PATCH 1/1] Staging: hv: storvsc: Move the storage driver out of the staging area

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Message-ID: <6E21E5352C11B742B20C142EB499E0481AA6D4CC@TK5EX14MBXC128.redmond.corp.microsoft.com>
Date:	Fri, 18 Nov 2011 23:28:19 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"virtualization@...ts.osdl.org" <virtualization@...ts.osdl.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"ohering@...e.com" <ohering@...e.com>,
	"hch@...radead.org" <hch@...radead.org>
Subject: RE: [PATCH 1/1] Staging: hv: storvsc: Move the storage driver out
 of the staging area



> -----Original Message-----
> From: James Bottomley [mailto:James.Bottomley@...senPartnership.com]
> Sent: Friday, November 18, 2011 12:01 PM
> To: KY Srinivasan
> Cc: gregkh@...e.de; linux-kernel@...r.kernel.org;
> devel@...uxdriverproject.org; virtualization@...ts.osdl.org; linux-
> scsi@...r.kernel.org; ohering@...e.com; hch@...radead.org
> Subject: RE: [PATCH 1/1] Staging: hv: storvsc: Move the storage driver out of the
> staging area
> 
> On Fri, 2011-11-18 at 04:53 +0000, KY Srinivasan wrote:
> > > I still think you need to disable clustering and junk the bvec merge
> > > function.  Your object seems to be to accumulate in page size multiples
> > > (and not aggregate over this) ... that's what clustering is designed to
> > > do.
> >
> > As part of addressing your first round of comments, I experimented with your
> > suggestions and I could not get rid of the code that does the bounce buffer
> handling.
> > I could generate I/O patterns that would require bounce buffer handling with
> your
> > suggestions in place.
> 
> There are two separate things here.  One is the scatter gather list
> bounce buffer processing, which is a bit nasty, but if you want to use <
> 4kb block size filesystems, I suppose I have to accept that you need it
> (although since it's a global fault of the hypervisor, perhaps it should
> sit in the hypervisor interface layer, so that every SG based transport
> can use it).  The other is the biovec merge function addition.  The
> purpose of this function seems to be to ensure you get one SG entry for
> every page (if I read it right)?  In that case, you don't need any of
> this special casing.  The flag DISABLE_CLUSTERING achieves the same
> thing.

Thanks James. I will keep you posted on my progress on this issue.

Regards,

K. Y