Namecache status report #3

[Gleb Kurtsou]

Last week I've fixed bugs and implemented missing bits to make cache
functional with tmpfs. I've spent some time trying to adapt it in
msdosfs, but wasn't successful because the code is too hard to work
with, the only useful experience was memo in todo list not to forget
about case insensitive filesystems and utf8 normalization in zfs.

So I've decided to give ext2fs a try, which is much easer to work with
and yet not too complicated. It went smooth except ext2_rename. Which
had races with dircache. After some experimenting I'm thinking about
changing API to decouple vnode/inode operations and export reference
counting. Currently dircache API is a mix of Solaris directory cache and
pefs dircache. I'm going to change the way of assigning vnode to cache
entry to resemble inner filesystem workings a bit more.

This week I'll add dircache to stackable filesystem, the aim is to add
filesystem private data to cache and define a method to validate cache
entries on lower layer.