generic/564: fix copy_range -f availability test

generic/564 wants to test for copy_range -f, but as it's implemented
it calls copy_range with a length of zero which will silently return
success from the VFS (at least on some kernels) even if the underlying
fs doesn't support it.

So patch this up 2 ways; perform the test with an explicit length
so it's not a no-op, and go ahead test copy_range w/o -f in the test
first just to be on the safe side (and for clearer failure messages.)

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

common/rc

@@ -2109,7 +2109,7 @@ _require_xfs_io_command()
 		if [ "$param" == "-f" ]; then
 			# source file is the open destination file
 			testcopy=$testfile
-			copy_opts="0 -d 4k"
+			copy_opts="0 -d 4k -l 4k"
 		fi
 		$XFS_IO_PROG -F -f -c "pwrite 0 4k" $testfile > /dev/null 2>&1
 		testio=`$XFS_IO_PROG -F -f -c "copy_range $param $copy_opts" $testcopy 2>&1`

tests/generic/564

@@ -49,6 +49,8 @@ _require_loop
 # copy source, as an indication that the test can run without hanging
 # with large size argument and to avoid opening pipe in blocking mode.
 #
+# Test both basic copy_range and copy_range -f availability
+_require_xfs_io_command "copy_range"
 _require_xfs_io_command "copy_range" "-f"
 
 testdir="$TEST_DIR/test-$seq"