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SubjectRe: vmalloc_32 and SLAB incompatible in 2.6.23.9
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"Loïc Grenié" <loic.grenie@gmail.com> writes:

> Since GFP_DMA32 is not considered a valid flag, vmalloc_32 and
> SLAB are incompatible in kernel 2.6.23.9 (and probably later ones).
> It might be as simple as adding GFP_DMA32 everywhere where
> GFP_DMA is used in mm/slab.c, but I don't dare do it. I personally
> switched to SLUB.

I don't think it would really work for slub either.

If you look at /proc/slabinfo you see that there are separate DMA
caches. That is because sl[abo]b all cache objects and if the
objects have different requirements (like GFP_DMA, GFP_DMA32, GFP_KERNEL)
they would need different caches. Otherwise you risk getting
later objects originally allocated with the wrong flags.

To make GFP_DMA32 work would require adding another set of DMA32
caches to all kmalloc caches etc or a separate one for each
custom kmem cache that you use that only gets _DMA32 objects.

Better just use __get_free_pages() directly.

-Andi
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