commit 0769663b4f580566ef6cdf366f3073dbe8022c39 upstream.

According to the NFSv4.2 spec if the input and output file is the
same file, operation should fail with EINVAL. However, linux
copy_file_range() system call has no such restrictions. Therefore,
in such case let's return EOPNOTSUPP and allow VFS to fallback
to doing do_splice_direct(). Also when copy_file_range is called
on an NFSv4.0 or 4.1 mount (ie., a server that doesn't support
COPY functionality), we also need to return EOPNOTSUPP and
fallback to a regular copy.

Fixes xfstest generic/075, generic/091, generic/112, generic/263
for all NFSv4.x versions.
Signed-off-by: NOlga Kornievskaia <kolga@netapp.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Cc: Yu Xu <xuyu@linux.alibaba.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>