The open call will still have to read through the directory to find
the current entry before it can start the inode fetch, as part of the
open, so this way, the inode should be present already.
The downside of this is that if there is a lot of reading of
directories without stating/opening the file, there will be a lot of
uselessly fetched inodes.
I think very few programs read directories without either opening or
stating the files, so this should be a general win.
On the other hand, open by inode, with inode in the directory would be
the ultimate fastested thing...