Functions compat_nfs_svc_trans, compat_nfs_clnt_trans,
compat_nfs_exp_trans, compat_nfs_getfd_trans and compat_nfs_getfs_trans,
which are called by compat_sys_nfsservctl(fs/compat.c), don't handle the
return value of access_ok properly.  access_ok return 1 when the addr is
valid, and 0 when it's not, but these functions have the reversed
understanding.  When the address is valid, they always return -EFAULT to
compat_sys_nfsservctl.

An example is to run /usr/sbin/rpc.nfsd(32bit program on Power5).  It
doesn't function as expected.  strace showes that nfsservctl returns
-EFAULT.

The patch fixes this by correcting the error handling on the return value
of access_ok in the five functions.

Signed-off-by: Lin Feng Shen <shenlinf@cn.ibm.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Acked-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>