I have tried to find information about the IFS before, actually for doing the same thing (an ext2fs driver for Win95, WinNT and DOS). These are the best references I found:
- Inside the Windows 95 File System by Stan Mitchell, O'Reilly in May '97 Gives many details (esp. on VFAT and IFSMgr) and includes Multimon, a tool to sniff on INTs, VXDs and so on.
- Systems Programming for Windows 95 by Walter Oney, Microsoft Press in '96 (he claims to have no affiliation with MS other that they published his book). Is more general than the above but has a very interesting chapter about the IFS. Describes how to write a VXD.
There are other interesting books about DOS/Windows internals, especially those written by Andrew Schulman and Geoff Chapell. (Write me if you need references).
I stopped working on this due to lack of time. But my approach started out as this: I was looking at the ext2tools, a package for DOS providing rudimetary ext2 access through special commands (like e2dir, e2cat and so on), without providing a drive letter. They were build from a snapshot of the ext2fs kernel sources, glued together with a library doing regular expressions (for filename matching) and getting a pointer to the partition through an environment variable. The disk accesses were done via the plain BIOS IRQ 13.
I wanted to make all of this into a drive letter based approach and wanted to put together the current ext2fs from the linux kernel, get a VXD running and answer IFS requests.
Someone else seems to have a read-only version of this running now. You should perhaps contact Peter van Sebille or read his page at http://www.globalxs.nl/home/p/pvs/. You can find the driver there as well.