linux-kernel - Re: [Bug #13319] Page allocation failures with b43 and p54usb

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Date:	Mon, 27 Jul 2009 02:37:13 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	Larry Finger <Larry.Finger@...inger.net>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Johannes Berg <johannes@...solutions.net>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [Bug #13319] Page allocation failures with b43 and p54usb

On Mon, 27 Jul 2009, Pekka Enberg wrote:

> > Hmm, I'm remembering differently.  I 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' tree.
> 
> 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.
> 

>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=O only disables debugging options that increase the min order 
of slab as defined in DEBUG_FLAGS; it doesn't selectively disable some of 
them when get_order(s->size) grows.  So it's quite sane, like my patch 
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 
minimum order, so I don't see DEBUG_FLAGS_SIZE as troublesome.

Christoph?