Balancing ttm_mem_io_reserve() and ttm_mem_io_free()

[Thomas Hellström]

Hi Christian,

I'm looking for a way to take some sort of reference across possible 
VRAM accesses  over the PCI bar, be it for runtime PM, workarounds or 
whatever.

The ttm_mem_io_reserve/free seems like a good candidate, but is 
completely unbalanced and looks racy. In particular error paths forget 
to call ttm_mem_io_free().

Would you have any objections if I took a look at attempting to balance 
calls to those functions, or do you have any other suggestions for a 
better method?

Thanks,

Thomas