Re: alpha iommu fixes

[Andi Kleen]

On Mon, May 21, 2001 at 03:00:24AM -0700, David S. Miller wrote:
>  > That's currently the case, but at least on IA32 the block layer
>  > must be fixed soon because it's a serious performance problem in
>  > some cases (and fixing it is not very hard).
> 
> If such a far reaching change goes into 2.4.x, I would probably
> begin looking at enhancing the PCI dma interfaces as needed ;-)

Hmm, I don't think it'll be a far reaching change. As far as I can see 
all it needs is a new entry point for block device drivers that uses 
bh->b_page. When that entry point exists skip the create_bounce call 
in __make_request. After that it is purely problem for selected drivers.

[BTW, the 2.4.4 netstack does not seem to make any attempt to handle the
pagecache > 4GB case on IA32 for sendfile, as the pci_* functions are dummies 
here.  It probably needs bounce buffers there for this case]

-Andi