linux-kernel - Re: can a kmalloc be both GFP_ATOMIC and GFP

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Message-ID: <Pine.LNX.4.64.0704292257080.2910@schroedinger.engr.sgi.com>
Date:	Sun, 29 Apr 2007 22:58:54 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	"Robert P. J. Day" <rpjday@...dspring.com>,
	"Shan, Guo Wen (Gavin)" <gshan@...atel-lucent.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: can a kmalloc be both GFP_ATOMIC and GFP_KERNEL at the same
 time?

On Sat, 28 Apr 2007, Alan Cox wrote:

> > > drivers/scsi/aic7xxx_old.c:  aic_dev = kmalloc(sizeof(struct aic_dev_data), GFP_ATOMIC | GFP_KERNEL);
> > > drivers/message/i2o/device.c:   resblk = kmalloc(buflen + 8, GFP_KERNEL | GFP_ATOMIC);
> > >
> > >   clarification?
> > 
> > oh, i'm *aware* of the definitions of those flags, but every single
> > source i've ever read has *strongly* suggested that you don't use
> 
> I don't believe either of those is doing what the author intended 8).

Well sortof. First of all kmalloc may not even allocate a page to 
satisfy the request. If it does then we do essentially GFP_KERNEL | 
__GFP_HIGH meaning a allocation where we can sleep etc but are allowed to 
dip into the reserves.

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