Fix partition resize for MBR (home-assistant#1149)

Partition handling for disks with 4k sectors broke partition resizing
when using MBR disk label. It seems that sfdisk doesn't calculate the
last LBA for diks with MBR label. Calculate the last usable LBA ourselfs
in the MBR case.

buildroot-external/rootfs-overlay/usr/libexec/hassos-expand

@@ -13,6 +13,7 @@ PART_NUM="$(cat "/sys/class/block/${DEVICE_CHILD_NAME}/partition")"
 # Get partition label type
 PART_TABLE="$(sfdisk -lqJ "${DEVICE_ROOT}")"
 PART_LABEL="$(echo "${PART_TABLE}" | jq -r '.partitiontable.label')"
+echo "[INFO] Checking if expanding data partition on ${DEVICE_CHILD} is necessary"
 
 if [ "${PART_LABEL}" = "gpt" ]; then
     echo "[INFO] Detected GPT partition label on ${DEVICE_ROOT}"
@@ -24,15 +25,21 @@ if [ "${PART_LABEL}" = "gpt" ]; then
         # Reload partition label to get correct .partitiontable.lastlba
         PART_TABLE="$(sfdisk -lqJ "${DEVICE_ROOT}")"
     fi
+    LAST_USABLE_LBA="$(echo "${PART_TABLE}" | jq -r '.partitiontable.lastlba')"
 else
     echo "[INFO] Detected MBR partition label on ${DEVICE_ROOT}"
-fi
 
-LAST_USABLE_LBA="$(echo "${PART_TABLE}" | jq -r '.partitiontable.lastlba')"
+    # For MBR, we have to calculate the last usable sector by ourselfs
+    DEVICE_SIZE=$(blockdev --getsize64 "${DEVICE_ROOT}")
+    SECTOR_SIZE=$(echo "${PART_TABLE}" | jq -r '.partitiontable.sectorsize')
+    LAST_USABLE_LBA="$((DEVICE_SIZE / SECTOR_SIZE))"
+fi
+echo "[INFO] Last usable logical block ${LAST_USABLE_LBA}"
 
 # Calculate end of data partition
 JQ_FILTER=".partitiontable.partitions[] | select ( .node == \"${DEVICE_CHILD}\" ) | .start + .size"
 DATA_PARTITION_END="$(echo "${PART_TABLE}" | jq "${JQ_FILTER}")"
+echo "[INFO] Data partition end block ${DATA_PARTITION_END}"
 
 # Need resize? Ignore free space if its less than 8MB/64MB (4k sectors) since
 # that could be partition alignment rounding...