From 97642738942de7f3e32b48e0d5aebf8a7cb0f1e8 Mon Sep 17 00:00:00 2001
From: Stefan Agner <stefan@agner.ch>
Date: Wed, 30 Dec 2020 18:12:44 +0100
Subject: [PATCH] Fix handling of disks with 4k sector size (#1141) (#1146)

The calculation whether to resize the partition only works with disks
with 512 byte sector size. Use values provided by sfdisk exclusively to
make sure comparing the same sector size.

Furthermore, it seems that sgdisk does not like sfdisk's backup GPT
placement:
$ sgdisk -e /dev/zram1
Warning! Secondary partition table overlaps the last partition by 250 blocks!

Today it seems sfdisk can handle GPT quite well. Use sfdisk for all
operations in hassos-expand.
---
 .../rootfs-overlay/usr/libexec/hassos-expand  | 40 ++++++++-----------
 1 file changed, 17 insertions(+), 23 deletions(-)

diff --git a/buildroot-external/rootfs-overlay/usr/libexec/hassos-expand b/buildroot-external/rootfs-overlay/usr/libexec/hassos-expand
index 1af9bf53c..77db8a771 100755
--- a/buildroot-external/rootfs-overlay/usr/libexec/hassos-expand
+++ b/buildroot-external/rootfs-overlay/usr/libexec/hassos-expand
@@ -15,22 +15,27 @@ PART_TABLE="$(sfdisk -lqJ "${DEVICE_ROOT}")"
 PART_LABEL="$(echo "${PART_TABLE}" | jq -r '.partitiontable.label')"
 
 if [ "${PART_LABEL}" = "gpt" ]; then
-    echo "[INFO] Detected GPT partition label"
-    # We cannot use .partitiontable.lastlba from the json output as we might
-    # still have the backup GPT not at the end of the disk. Calculate last
-    # usable LBA using disk size
-    LAST_USABLE_LBA=$(( $(cat "/sys/class/block/${DEVICE_ROOT_NAME}/size") - 34 ))
+    echo "[INFO] Detected GPT partition label on ${DEVICE_ROOT}"
+
+    if sfdisk --verify "${DEVICE_ROOT}" 2>&1 | grep "The backup GPT table is not on the end of the device."; then
+        echo "[INFO] Moving GPT backup header to the end"
+        sfdisk --relocate gpt-bak-std "${DEVICE_ROOT}"
+
+        # Reload partition label to get correct .partitiontable.lastlba
+        PART_TABLE="$(sfdisk -lqJ "${DEVICE_ROOT}")"
+    fi
 else
-    echo "[INFO] Detected MBR partition label"
-    LAST_USABLE_LBA=$(cat "/sys/class/block/${DEVICE_ROOT_NAME}/size")
+    echo "[INFO] Detected MBR partition label on ${DEVICE_ROOT}"
 fi
 
+LAST_USABLE_LBA="$(echo "${PART_TABLE}" | jq -r '.partitiontable.lastlba')"
+
 # Calculate end of data partition
 JQ_FILTER=".partitiontable.partitions[] | select ( .node == \"${DEVICE_CHILD}\" ) | .start + .size"
 DATA_PARTITION_END="$(echo "${PART_TABLE}" | jq "${JQ_FILTER}")"
 
-# Need resize? Ignore everything less than 8MB since that could be partition
-# alignment rounding...
+# Need resize? Ignore free space if its less than 8MB/64MB (4k sectors) since
+# that could be partition alignment rounding...
 UNUSED_BLOCKS=$(( LAST_USABLE_LBA - DATA_PARTITION_END ))
 if [ "${UNUSED_BLOCKS}" -le "16384" ]; then
     echo "[INFO] No resize of data partition needed"
@@ -38,21 +43,10 @@ if [ "${UNUSED_BLOCKS}" -le "16384" ]; then
 fi
 
 echo "[INFO] Update hassos-data partition ${PART_NUM}"
-if [ "${PART_LABEL}" = "gpt" ]; then
-    sgdisk -e "${DEVICE_ROOT}"
-    sgdisk -d "${PART_NUM}" \
-        -n "${PART_NUM}:0:0" \
-        -c "${PART_NUM}:hassos-data" \
-        -t "${PART_NUM}:0FC63DAF-8483-4772-8E79-3D69D8477DE4" \
-        -u "${PART_NUM}:a52a4597-fa3a-4851-aefd-2fbe9f849079" \
-        "${DEVICE_ROOT}"
-    sgdisk -v "${DEVICE_ROOT}"
-else
-    echo ", +" | sfdisk -N "${PART_NUM}" "${DEVICE_ROOT}" --force
-    sfdisk -V "${DEVICE_ROOT}"
-fi
+echo ", +" | sfdisk --no-reread --no-tell-kernel -N "${PART_NUM}" "${DEVICE_ROOT}"
+sfdisk -V "${DEVICE_ROOT}"
 
-# Reload partition table
+# Update the kernel's partition table
 partx -u "${DEVICE_ROOT}"
 udevadm settle