[PATCH] Fix swiotlb pci_map_sg error handling

The overflow checking condition in lib/swiotlb.c was wrong.
It would first run a NULL pointer through virt_to_phys before
testing it. Since pci_map_sg overflow is not that uncommon
and causes data corruption (including broken file systems) when not
properly detected I think it's better to fix it in 2.6.15.

This affects x86-64 and IA64.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>