Marc Singer wrote:
I'm investigating why I am triggering a BUG_ON in split_page() when I
use the sound subsystems dma memory allocation aide.
The crux of the problem appears to be that snd_malloc_dev_pages()
passes __GFP_COMP into dma_alloc_coherent(). On the ARM and several
other architectures, the dma allocation code calls split_page () with
pages allocated with this flag which, in turn, triggers the BUG_ON()
check for the CompoundPage flag.
So, the questions are these: Who is doing the wrong thing? Should the
snd_malloc_dev_pages() call drop the __GFP_COMP flag? Should
split_page() allow the page to be compound? Should __GFP_COMP be 0 on
ARM and other architectures that don't support compound pages?
I personally never liked the explicit __GFP_COMP going in everywhere,
and would have much preferred a GFP_USERMAP, which the architecture /
allocator could satisfy as they liked.
As a hack, you can make arm's dma_alloc_coherent() drop __GFP_COMP,
which should work.
--
SUSE Labs, Novell Inc.
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