Jeff,
FYI, I tried your patch; it causes the lvm process called out of
the initramfs from an Ubuntu 8.10 system to blow up while trying to
set up the root filesystem. The stack trace was:
generic_make_request+0x2a3/0x2e6
trace_hardirqs_on_caller+0x111/0x135
mempool_alloc_slab+0xe/0x10
mempool_alloc+0x42/0xe0
submit_bio+0xad/0xb5
bio_alloc_bioset+0x21/0xfc
blkdev_issue_flush+0x7f/0xfc
syn_blockdev+0x2a/0x36
__blkdev_put_0x44/0x131
blkdev_put+0xa/0xc
blkdev_close+0x2e/0x32
__fput+0xcf/0x15f
fput+0x19/0x1b
filp_close+0x51/0x5b
sys_close+0x73/0xad