Re: Is sendfile all that sexy?

[kuznet@ms2.inr.ac.ru]

Hello!

> "struct page" tricks, some macros etc WILL NOT WORK. In particular, we do
> not currently have a good "page_to_bus/phys()" function. That means that
> anybody trying to do DMA to this page is currently screwed, simply because
> he has no good way of getting the physical address.

We already have similar problem with 64bit dma on Intel.
Namely, we need page_to_bus() and, moreover, we need 64bit bus addresses
for devices understanding them.

Now we make this in acenic like:

#if defined(CONFIG_X86) && defined(CONFIG_HIGHMEM)

#define BITS_PER_DMAADDR 64

typedef unsigned long long dmaaddr_high_t;

static inline dmaaddr_high_t
pci_map_single_high(struct pci_dev *hwdev, struct page *page,
		    int offset, size_t size, int dir)
{
	dmaaddr_high_t phys;

	phys = (page-mem_map) *
		(unsigned long long) PAGE_SIZE +
			offset;

	return phys;
}

#else


Ingo, do you remember, that we agreed not to consider this code
as "ready for release" until this issue is not cleaned up?
I forgot this. 8)8)8)

Seems, we can remove at least direct dependencies on mem_map
using zone_struct.

Alexey
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