radix-tree pagecache for 2.4.19-pre4-ac1

Hi.

Here' the patch for the latest -ac kernel. This version of the patch incorporates nearly all the changes listed in the following message ...

http://mail.nl.linux.org/linux-mm/2002-03/msg00043.html

The changes for vmscan.c weren't applied, as that part of the original patch was dropped due to differences between rmap and non-rmap code.

I'm running the 2.4.19-pre4-ac1 kernel with the patch now, and had been running a 2.4.19-pre3-ac6 kernel with Andrew's fixes for most of the day. The patch below should apply cleanly to -pre4-ac1. Enjoy!

They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety.
 -- Benjamin Franklin, Historical Review of Pennsylvania, 1759