This patch is for patching the mm and fs stuff to make the Linux 2.4.21
swap code to allow a concept of modularized swap methods. This concept
and swap code is originally from Justus Heine who created the NFS swap
patch for 2.2 and 2.4 . I've extracted the code and modified to make it
as a generic swap module code. The vanilla kernel swap code is been
moved to a file fs/blkdev_swap.c which is for normal plain block device
swaps. Users can configure the kernel to include the local block device
swap code or compile it as a module. Developers can also develop their
own swap methods instead of using the plain swap code (may be some
crypto for security reasons) . I've been using this API to develop NFS
swap and netswap code for a year an more. This patch has been tested for more than a year in a production environment on smp and non-smp (I think it is quite stable though). Please find it useful.