NFSv4.1 fix incorrect return value in copy_file_range

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: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs42proc.c

@@ -329,9 +329,6 @@ ssize_t nfs42_proc_copy(struct file *src, loff_t pos_src,
 	};
 	ssize_t err, err2;
 
-	if (!nfs_server_capable(file_inode(dst), NFS_CAP_COPY))
-		return -EOPNOTSUPP;
-
 	src_lock = nfs_get_lock_context(nfs_file_open_context(src));
 	if (IS_ERR(src_lock))
 		return PTR_ERR(src_lock);

fs/nfs/nfs4file.c

@@ -133,8 +133,10 @@ static ssize_t nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
 				    struct file *file_out, loff_t pos_out,
 				    size_t count, unsigned int flags)
 {
+	if (!nfs_server_capable(file_inode(file_out), NFS_CAP_COPY))
+		return -EOPNOTSUPP;
 	if (file_inode(file_in) == file_inode(file_out))
-		return -EINVAL;
+		return -EOPNOTSUPP;
 	return nfs42_proc_copy(file_in, pos_in, file_out, pos_out, count);
 }