throtl/rc,002: adjust to scsi_debug

Currently, the test case throtl/002 assumes that the test target device
is null_blk. For null_blk, it is possible to specify the page size as
the maximum I/O size during set up. However, in the case of scsi_debug,
the maximum I/O size is not configurable, causing the test case to fail
when the test case is extended to support scsi_debug.

To prevent the failure, set the maximum I/O size after the test device
is initialized, regardless of the device type. To achieve this, add a
new helper function _throtl_set_max_io_size() which modifies the sysfs
attribute max_sectors_kb to adjust the maximum I/O size for the device.

Suggested-by: Yu Kuai <[email protected]>
Reviewed-by: Chaitanya Kulkarni <[email protected]>
Signed-off-by: Shin'ichiro Kawasaki <[email protected]>

Author: kawasaki

tests/throtl/002

@@ -24,7 +24,10 @@ test() {
 	fi
 
 	io_size_kb=$(($(_throtl_get_max_io_size) * 1024))
-	block_size=$((iops * io_size_kb))
+	if [ "${io_size_kb}" -gt "${page_size}" ]; then
+		_throtl_set_max_io_size $((page_size / 1024))
+	fi
+	block_size=$((iops * page_size))
 
 	_throtl_set_limits wiops="${iops}"
 	_throtl_test_io write "${block_size}" 1

tests/throtl/rc

@@ -114,6 +114,10 @@ _throtl_get_max_io_size() {
 	cat "/sys/block/$THROTL_DEV/queue/max_sectors_kb"
 }
 
+_throtl_set_max_io_size() {
+	echo "$1" > "/sys/block/$THROTL_DEV/queue/max_sectors_kb"
+}
+
 _throtl_issue_fs_io() {
 	local path=$1
 	local start_time