Re: can a kmalloc be both GFP_ATOMIC and GFP_KERNEL at the sametime?
From: Andrew Morton
Date: Mon Apr 30 2007 - 13:02:50 EST
On Mon, 30 Apr 2007 04:46:54 -0400 (EDT) "Robert P. J. Day" <rpjday@xxxxxxxxxxxxxx> wrote:
> On Mon, 30 Apr 2007, Andrew Morton wrote:
> > On Sat, 28 Apr 2007 09:40:39 -0400 (EDT) "Robert P. J. Day" <rpjday@xxxxxxxxxxxxxx> wrote:
> > >
> > > i'd always assumed that the type flags of GFP_ATOMIC and GFP_KERNEL
> > > were mutually exclusive when it came to calling kmalloc(), at least
> > > based on everything i'd read. so i'm not sure how to interpret the
> > > following:
> > >
> > > 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?
> > GFP_ATOMIC implies that the memory comes from the zones which
> > GFP_KERNEL also uses. So the above usage of GFP_KERNEL is redundant
> > and should be removed.
> hang on ... based on an email i just got, is that reference to
> GFP_KERNEL "redundant" or "conflicting"? big difference there. and
> is the proper fix to remove "GFP_KERNEL" in both cases?
umm, yeah, oops. GFP_KERNEL|GFP_ATOMIC is not a redundant combination.
It's GFP_KERNEL plus "is able to access emergency pools". We'd normally
represent that as GFP_KERNEL|__GFP_HIGH.
However it's questionable whether that was the intent in those two drivers.
`git-blame' might tell.
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