linux-kernel - Re: __get_free_pages: can GFP_DMA omit GFP_KERNEL and GFP

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Message-ID: <Pine.LNX.4.64.0706041449470.3148@localhost.localdomain>
Date:	Mon, 4 Jun 2007 14:53:19 -0400 (EDT)
From:	"Robert P. J. Day" <rpjday@...dspring.com>
To:	Christoph Lameter <clameter@....com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: __get_free_pages:  can GFP_DMA omit GFP_KERNEL and GFP_ATOMIC?

On Mon, 4 Jun 2007, Christoph Lameter wrote:

> On Sun, 3 Jun 2007, Robert P. J. Day wrote:
>
> >   first, can a call to __get_free_pages to allocate DMA-able
> > memory omit specifying either of GFP_KERNEL or GFP_ATOMIC?
> > love's book on kernel development strongly suggests you need to
> > specify one or the other, but there are a few instances in the
> > tree like this:
>
> Sure that seems to be equivalent to GFP_ATOMIC with no access to
> emergency pool memory.
>
> >   and, second, i only noticed this as i was going to submit a
> > short patch to replace __get_free_pages calls for DMA-able memory
> > with the existing equivalent macro __get_dma_pages.  is that still
> > considered a worthwhile cleanup?  there's not that many examples
> > of it, and it would just make things consistent.
>
> Sure.

all right, then some of those __get_free_pages() calls would translate
to calls of the form __get_dma_pages(0, ...) -- is that what you're
saying?  or would it be equivalent and preferable to put GFP_ATOMIC in
there just so it looks not so weird?

rday
--
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

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