Re: [PATCH] x86: adjust GFP mask handling for coherent allocations

[Jan Beulich]

>>> FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> 27.10.09 10:11 >>>
>If a driver doesn't want to GFP_DMA, it should set up the
>dma_coherent_mask of the device and pass it. In fact, it should do. A
>driver that uses the fallback device is broken.

Agreed.

>Why can't you fix drivers that use the fallback instead of adding
>another hack to the common place?

Because there's quite a few of them - just search for callers of
dma_alloc_coherent() passing NULL as the first argument. Of course
I'd rather see the fallback gone, but I think this requires cooperation
from/action taken by the driver maintainers first. A first step might be
to add a WRN_ON() for that case, but I don't see it being reasonable
to eliminate the fallback right away. Hence, with it having got broken
in .26 I think it is reasonable to fix it for the time being.

Jan

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