dmhugedisk: Allow specifying of chunk size

Ext4 will want to use dmhugedisk infrastructure for testing resize
bugs.  Ext4 fs images are rather sparse (especially with smaller
block sizes) so the current chunk size of 512 sectors leads to large
space consumption.  Allow test to specify chunk size.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

common/dmhugedisk

@@ -31,6 +31,11 @@ _dmhugedisk_init()
 {
 	test -z "$1" && _fatal "must specify sector count to _dmhugedisk_init"
 	local dm_backing_dev=$SCRATCH_DEV
+	local chunk_size="$2"
+
+	if [ -z "$chunk_size" ]; then
+		chunk_size=512
+	fi
 
 	$DMSETUP_PROG remove huge-test > /dev/null 2>&1
 	$DMSETUP_PROG remove huge-test-zero > /dev/null 2>&1
@@ -41,7 +46,7 @@ _dmhugedisk_init()
 	DMHUGEDISK_DEV='/dev/mapper/huge-test'
 
 	DMHUGEDISK_ZERO_TABLE="0 $blk_dev_size zero"
-	DMHUGEDISK_DEV_TABLE="0 $blk_dev_size snapshot $DMHUGEDISK_ZERO $SCRATCH_DEV N 512"
+	DMHUGEDISK_DEV_TABLE="0 $blk_dev_size snapshot $DMHUGEDISK_ZERO $SCRATCH_DEV N $chunk_size"
 
 	$DMSETUP_PROG create huge-test-zero --table "$DMHUGEDISK_ZERO_TABLE" || \
 		_fatal "failed to create dm huge zero device"