o_direct-14 and blkdev-pagecache-14
You can find the latest O_DIRECT and blkdev in pagecache patches against vanilla 2.4.9 here (not only in -aa):
ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/patches/v2.4/2.4.9/o_direct-14 ftp://ftp.us.kernel.org/pub/linux/kernel/people/andrea/patches/v2.4/2.4.9/blkdev-pagecache-14
As usual the blkdev-pagecache patch depends on o_direct so it is an incremental patch.
Thanks to Janet Morgan for the O_DIRECT auditing.
Andrea