+static unsigned long long find_size(struct extent *e, int *idx, int num_extents)
+{
+ const unsigned long long base_start = e[*idx].start;
+ unsigned long long end = base_start + e[*idx].size;
+ int i;
+
+ if (base_start == end)
+ return 0;
+
+ *idx = *idx + 1;
+ for (i = *idx; i < num_extents; i++) {
+ /* extend overlapping extents */
+ if (e[i].start >= base_start &&
+ e[i].start <= end) {
+ if (e[i].size == 0)
+ return 0;
+ if (e[i].start + e[i].size > end)
+ end = e[i].start + e[i].size;
+ } else if (e[i].start > end) {
+ *idx = i;
+ break;
+ }
+ }
+
+ return end - base_start;
+}
+
+static unsigned long long merge_extents(struct intel_super *super, int sum_extents)
+{
+ /* build a composite disk with all known extents and generate a new
+ * 'maxsize' given the "all disks in an array must share a common start
+ * offset" constraint
+ */
+ struct extent *e = calloc(sum_extents, sizeof(*e));
+ struct dl *dl;
+ int i, j;
+ int start_extent;
+ unsigned long long pos;
+ unsigned long long start;
+ unsigned long long maxsize;
+ unsigned long reserve;
+
+ if (!e)
+ return ~0ULL; /* error */
+
+ /* coalesce and sort all extents. also, check to see if we need to
+ * reserve space between member arrays
+ */
+ j = 0;
+ for (dl = super->disks; dl; dl = dl->next) {
+ if (!dl->e)
+ continue;
+ for (i = 0; i < dl->extent_cnt; i++)
+ e[j++] = dl->e[i];
+ }
+ qsort(e, sum_extents, sizeof(*e), cmp_extent);
+
+ /* merge extents */
+ i = 0;
+ j = 0;
+ while (i < sum_extents) {
+ e[j].start = e[i].start;
+ e[j].size = find_size(e, &i, sum_extents);
+ j++;
+ if (e[j-1].size == 0)
+ break;
+ }
+
+ pos = 0;
+ maxsize = 0;
+ start_extent = 0;
+ i = 0;
+ do {
+ unsigned long long esize;
+
+ esize = e[i].start - pos;
+ if (esize >= maxsize) {
+ maxsize = esize;
+ start = pos;
+ start_extent = i;
+ }
+ pos = e[i].start + e[i].size;
+ i++;
+ } while (e[i-1].size);
+ free(e);
+
+ if (start_extent > 0)
+ reserve = IMSM_RESERVED_SECTORS; /* gap between raid regions */
+ else
+ reserve = 0;
+
+ if (maxsize < reserve)
+ return ~0ULL;
+
+ super->create_offset = ~((__u32) 0);
+ if (start + reserve > super->create_offset)
+ return ~0ULL; /* start overflows create_offset */
+ super->create_offset = start + reserve;
+
+ return maxsize - reserve;
+}
+