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

[Christoph Lameter]

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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