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From: David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Subject: Re: [Bug #13319] Page allocation failures with b43 and p54usb
Date: Mon, 27 Jul 2009 02:37:13 -0700 (PDT)
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To: Pekka Enberg <penberg-bbCR+/B0CizivPeTLB3BmA@public.gmane.org>
Cc: Larry Finger <Larry.Finger-tQ5ms3gMjBLk1uMJSBkQmQ@public.gmane.org>, "Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org>, Linux Kernel Mailing List <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Kernel Testers List <kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Johannes Berg <johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org>, Christoph Lameter <cl-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>

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On Mon, 27 Jul 2009, Pekka Enberg wrote:

> > Hmm, I'm remembering differently. =A0I thought the root problem here has
> > only been fixed in Pekka's slab-2.6.git tree with "slub: add option to
> > disable higher order debugging slabs" and isn't currently in Linus' tre=
e.
>=20
> Yup, the fix is in slab.git and queued for 2.6.32. There was some
> complaints from Christoph from the patch that need to be addressed
> still.
>=20

>From what I recall, he asked that calculate_sizes() be called twice, first =

to determine if get_order(s->size) increased as the result of the metadata =

and, if so, a second time with the flags disabled.

slab_debug=3DO only disables debugging options that increase the min order =

of slab as defined in DEBUG_FLAGS; it doesn't selectively disable some of=20
them when get_order(s->size) grows.  So it's quite sane, like my patch=20
does, to disable all DEBUG_FLAGS when

	get_order(s->objsize) + DEBUG_SIZE_FLAGS > get_order(s->objsize)

without calling calculate_sizes() twice.

We need DEBUG_FLAGS to determine which flags to mask off to reduce the=20
minimum order, so I don't see DEBUG_FLAGS_SIZE as troublesome.

Christoph?
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