linux-kernel - RE: [PATCH] [scsi] Remove __GFP

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Message-ID: <AE4F746F2AECFC4DA4AADD66A1DFEF019E1BDA@otce2k301.adaptec.com>
Date:	Wed, 23 May 2007 15:17:08 -0400
From:	"Salyzyn, Mark" <mark_salyzyn@...ptec.com>
To:	"James Bottomley" <James.Bottomley@...elEye.com>,
	"Aubrey Li" <aubreylee@...il.com>
Cc:	"Christoph Lameter" <clameter@....com>,
	"Bernhard Walle" <bwalle@...e.de>, <linux-scsi@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] [scsi] Remove __GFP_DMA

The 31 bit limit for some of these cards is a problem, we currently only
do __GFP_DMA for bounce buffer sg elements allocated for user supplied
references in ioctls.

I figure we should be using pci_alloc_consistent calls for these
allocations to more accurately acquire memory within the 31 bit limit if
necessary, we could switch to these to remove the need for the __GFP_DMA
flag in the aacraid driver?

-- Mark

-----Original Message-----
From: linux-scsi-owner@...r.kernel.org
[mailto:linux-scsi-owner@...r.kernel.org] On Behalf Of James Bottomley
Sent: Wednesday, May 23, 2007 11:18 AM
To: Aubrey Li
Cc: Christoph Lameter; Bernhard Walle; linux-scsi@...r.kernel.org;
Andrew Morton; linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [scsi] Remove __GFP_DMA

On Wed, 2007-05-23 at 10:41 +0800, Aubrey Li wrote:
> On 5/23/07, Christoph Lameter <clameter@....com> wrote:
> > On Mon, 21 May 2007, Bernhard Walle wrote:
> >
> > > [PATCH] [scsi] Remove __GFP_DMA
> > >
> > > After 821de3a27bf33f11ec878562577c586cd5f83c64, it's not necessary
to alloate a
> > > DMA buffer any more in sd.c.
> > >
> > > Signed-off-by: Bernhard Walle <bwalle@...e.de>
> >
> > Great that avoids a DMA kmalloc slab. Any other GFP_DMAs left in the
scsi
> > layer?
> >
> > Acked-by: Christoph Lameter <clameter@....com>
> 
> Yes, here is another patch

I'll defer to Mark on this one.  However, please remember that you can't
just blindly remove GFP_DMA ... there are some cards which require it.

Aacraid is one example ... it has a set of cards that can only DMA to 31
bits.  For them, the GFP_DMA is necessary:  The allocation in question
is a scatterlist, which must be within the device DMA mask.

James


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