Shrink the UMS partition to get space for the bigger FACTORYFS

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>

1 files changed, 70 insertions, 0 deletions

diff --git a/main.c b/main.c
index 9eb060f..46bd9ee 100644
--- a/main.c
+++ b/main.c
@@ -174,6 +174,69 @@ int grow_partition(void *buffer, size_t buffer_size, char *name,
 	return 0;
 }
 
+int shrink_partition(void *buffer, size_t buffer_size,
+		     char *name, size_t bytes)
+{
+	struct pit_partition_v2 *partition;
+	size_t offset;
+	size_t partition_nr_blocks;
+	size_t nr_extra_blocks = bytes / 512;
+
+	if (bytes % 512) {
+		printf("%s: \"%s\" error: %s size %d is not a multiple of 512\n",
+		       __func__, name, "bytes", bytes);
+		return -1;
+	}
+
+	offset = find_partition(buffer, buffer_size, name);
+	if (offset == -1) {
+		printf("%s: \"%s\" partition not found\n",
+		       __func__, name);
+		return -1;
+	}
+	partition = buffer + offset;
+
+	if (partition->nr_blocks < nr_extra_blocks) {
+		printf("%s: error: partition \"%s\" is too small:"
+		       " found size %d\n",
+		       __func__, name,
+		       512*le32toh(partition->nr_blocks));
+		return -1;
+	}
+
+	printf("%s: shrinking \"%s\" from %d to %d blocks\n",
+	       __func__, partition->name,
+	       le32toh(partition->nr_blocks),
+	       le32toh(partition->nr_blocks) - nr_extra_blocks);
+	partition_nr_blocks = le32toh(partition->nr_blocks) - nr_extra_blocks;
+	partition->nr_blocks = htole32(partition_nr_blocks);
+
+	do {
+		size_t new_offset = 0;
+
+		offset = find_next_partition(buffer, buffer_size, offset);
+		if (offset == -1)
+			break;
+
+		partition = buffer + offset;
+
+		if (partition->nr_blocks == 0)
+			continue;
+
+		new_offset = le32toh(partition->start_block) - nr_extra_blocks;
+
+		printf("%s: moving \"%s\" from 0x%x to 0x%x\n",
+		       __func__,
+		       partition->name,
+		       le32toh(partition->start_block),
+		       new_offset);
+		partition->start_block = new_offset;
+	}
+	while (true);
+
+	return 0;
+}
+
 int main()
 {
 	int fd;
@@ -224,6 +287,13 @@ int main()
 		return rc;
 	}
 
+	rc = shrink_partition(orig, orig_size, "UMS", 512*1024*1024);
+	if (rc == -1) {
+		printf("%s: modify_partitions failed with error %d\n",
+		       __func__, rc);
+		return rc;
+	}
+
 	rc = munmap(orig, orig_size);
 	if (rc == -1) {
 		rc = errno;