On Wed, 22 Jul 2009, Linus Torvalds wrote:
If you have ext3, you'd do something like
tune2fs -O dir_index /dev/<node-of-your-filesystem-goes-here>
One last email note on this subject. Really. Promise.
If you do that "tune2fs -O dir_index" thing, it will only take effect for
_newly_ created directories. So you'll still need to do that whole
"mv+cp+rm" dance, just to make sure that the refs directories are all new.
I think you can also force all directories to be indexed by using fsck,
but I forget the details. I'm sure man-pages will have it. Or google.
Linus