Passes usertests and stressfs
Seems to recover correctly in a number of simple cases

usertest that passes too many arguments, break exec

do not keep sorted contiguous free list

nits in comments

PDF at http://am.lcs.mit.edu/~rsc/xv6.pdf

Various changes made while offline.

 + bwrite sector argument is redundant; use b->sector.
 + reformatting of files for nicer PDF page breaks
 + distinguish between locked, unlocked inodes in type signatures
 + change FD_FILE to FD_INODE
 + move userinit (nee proc0init) to proc.c
 + move ROOTDEV to param.h
 + always parenthesize sizeof argument

delete unused functions
a few comments

checkpoint: write(fd,"hello\n",6) where fd is a console dev almost works

iget
mkfs makes a file system image
put this in your .bochsrc:
ata0-slave: type=disk, mode=flat, path="fs.img", cylinders=1024, heads=1, spt=1

pipes

and plan 9 code, at least boots and gets into C code.