linux-kernel - Re: tipc_init(), WARNING: at arch/x86/mm/highmem_32.c:52, [2.6.24-rc4-git5: Reported regressions from 2.6.23]

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Message-Id: <20071208100950.a3547868.akpm@linux-foundation.org>
Date:	Sat, 8 Dec 2007 10:09:50 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Matt Mackall <mpm@...enic.com>, Ingo Molnar <mingo@...e.hu>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <clameter@....com>
Subject: Re: tipc_init(), WARNING: at arch/x86/mm/highmem_32.c:52,
 [2.6.24-rc4-git5: Reported regressions from 2.6.23]

On Sat, 8 Dec 2007 09:54:06 -0800 (PST) Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Sat, 8 Dec 2007, Linus Torvalds wrote:
> > 
> > But I'll apply it anyway, because it looks "obviously correct" from the 
> > standpoint that the _other___slob user already clears the end result 
> > explicitly later on, and we simply should never pass down __GFP_ZERO to 
> > the actual page allocator.
> 
> Actually, I take that back. The other slob users are different. They share 
> pages, this codepath does not.
> 
> So I think a more proper solution would be:
>  (a) Something like this patch (which includes my previous mm/slub.c 
>      change)
>  (b) don't warn about atomic GFP_ZERO's - unless they have GFP_HIGHMEM set 
>      *too*.
> 
> So which warning is it that triggers the bogus error?

It's a kmap_atomic() debugging patch which I wrote ages ago and whcih Ingo
sucked into his tree.  I don't _think_ this warning is present in your tree
at all.

http://lkml.org/lkml/2007/11/29/157 is where it starts.

I had a lenghty back-and-forth with Christoph on this within the past
couple of months and I cannot locate the thread and I don't recall what the
upshot was and Christoph is still offline.

Knocking out __GFP_ZERO at the point where the slab allocator(s) call the
page allocator seems like a good approach to me.

But I don't think we need to do anything for 2.6.24..
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