Currently nfsd only worries about read-only exports for
directories and files, which allows device special files
to be chmodded (for example).

This patch extends the test to cover all files, but is careful
to avoid it when an IRIX client is doing an write-permission test
against a pre-existing device special file.

We encode that status in the return value.

Also, don't pass 'proc' parameter to ->accept, as it is
implicit in rqstp.

If one of the callback (e.g. data ready) is called
before socket setup is complete, oops may occur.

With this patch, socket is kept SK_BUSY until all is
ready to avoid this.

Also some code is moved around to make it cleaner.

into home.transmeta.com:/home/torvalds/v2.5/linux