implementation of getpages and putpages and the use of UBC in the read and
write operations), the worst problem has gone away which was a panic when
a file's contents were modified in the original file system and then read
through the NFS mount point.
Also remove the entry about optimization. While tmpfs still has room for
improvement, it has become a lot better lately, thanks to the string pools
and the changes yamt@ did in the anonymous objects handling.
e230b755b3