block highmem zero bounce v15

Hi,

I've uploaded a new version of the patch that allows direct I/O to highmem memory without resorting to bouncing to lower memory. Changes since last time include:

- Update to 2.4.10

- Fix SCSI dont-merge error. No corruption, just a performance hit (me)

- Add single_sg_ok entry to SCSI hosts. An alternative solution would be to always bounce single entry sg for highmem pages, however I don't want decent drivers to take a hit on account of crap drivers. Now the entire I/O path should be unaffected for non-highmem enabled hosts/drivers. (me)

ATM only aic7xxx and sym53c8xxx have single_sg_ok enabled, others will follow on a per-audit basis.

*.kernel.org/pub/linux/kernel/people/axboe/patches/2.4.10/block-highmem-all-15

Jens Axboe