linux-kernel - Re: Oops in a driver while using SLUB as a SLAB allocator

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Message-ID: <Pine.LNX.4.64.0706211759550.11554@schroedinger.engr.sgi.com>
Date:	Thu, 21 Jun 2007 18:01:32 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Hugh Dickins <hugh@...itas.com>
cc:	Nicolas Ferre <nicolas.ferre@....atmel.com>,
	ARM Linux Mailing List 
	<linux-arm-kernel@...ts.arm.linux.org.uk>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Marc Pignat <marc.pignat@...s.ch>,
	Andrew Victor <andrew@...people.com>,
	Pierre Ossman <drzeus@...eus.cx>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Oops in a driver while using SLUB as a SLAB allocator

On Thu, 21 Jun 2007, Hugh Dickins wrote:

> > The oops seems to occur after a page unmapping using dma_unmap_page() followed
> > by a flush_dcache_page() (in at91mci_post_dma_read()).

Was the page allocated using slab calls?

> Seems a little odd that it's gone throughout 2.6.22-rc unnoticed
> until now - nobody else trying SLUB on ARM or PA-RISC yet perhaps.
> As I understand it, you're not doing anything wrong (disclaimer:
> I'm no expert on dma_mapping things), but SLUB's reuse of struct
> page fields has collided with what flush_dcache_page is expecting.
> 
> Here's a patch: I'm not convinced it's necessarily the best one
> (most uses of page_mapping will never see a slab page, it's a pity
> to be cluttering up that inline even further); but in case nobody
> else can provide a better...

Well one may be better off allocating pages using the page allocator 
instead of the slab allocator. I removed these things from i386 but I did 
not check ARM.

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