+/*
+ * Like is_allocated_sectors, but if the buffer starts with a used sector,
+ * up to 'min' consecutive sectors containing zeros are ignored. This avoids
+ * breaking up write requests for only small sparse areas.
+ */
+static int is_allocated_sectors_min(const uint8_t *buf, int n, int *pnum,
+ int min)
+{
+ int ret;
+ int num_checked, num_used;
+
+ if (n < min) {
+ min = n;
+ }
+
+ ret = is_allocated_sectors(buf, n, pnum);
+ if (!ret) {
+ return ret;
+ }
+
+ num_used = *pnum;
+ buf += BDRV_SECTOR_SIZE * *pnum;
+ n -= *pnum;
+ num_checked = num_used;
+
+ while (n > 0) {
+ ret = is_allocated_sectors(buf, n, pnum);
+
+ buf += BDRV_SECTOR_SIZE * *pnum;
+ n -= *pnum;
+ num_checked += *pnum;
+ if (ret) {
+ num_used = num_checked;
+ } else if (*pnum >= min) {
+ break;
+ }
+ }
+
+ *pnum = num_used;
+ return 1;
+}
+