generic_setlease and tmpfs -- LTP fcntl failure

[Kumar Gala <galak@kernel.crashing.org>]

In debugging a LTP failure related to fcntl on tmpfs it appears that  
we aren't able to use fcntl(fd, F_SETLEASE, F_WRLCK).  In the  
debugging it looks like we artificial increase the dentry->d_count  
and so generic_setlease() always fails with -EAGAIN since it appears  
dentry->d_count will be 2.

This is my first time delving into fs code so I'm not that familiar  
with why tmpfs is artificially increasing the d_count.  I was  
wondering what a possible solution would be.

Maybe something like:

shmem_setlease(...) {
	if (arg == F_WRLCK) {
		dput(dentry)
		generic_setlease(...)
		dget(dentry)
	} else {
		generic_setlease(...)
	}
}

Not sure what harm doing the dput() / dget() will have.

- k