- /* Check EXTENT_DATA datasum */
- ret = count_csum_range(root, disk_bytenr, disk_num_bytes, &found);
- if (found > 0 && nodatasum) {
+ /*
+ * Check EXTENT_DATA csum
+ *
+ * For plain (uncompressed) extent, we should only check the range
+ * we're referring to, as it's possible that part of prealloc extent
+ * has been written, and has csum:
+ *
+ * |<--- Original large preallocated extent A ---->|
+ * |<- Prealloc File Extent ->|<- Regular Extent ->|
+ * No csum Has csum
+ *
+ * For compressed extent, we should check the whole range.
+ */
+ if (!compressed) {
+ search_start = disk_bytenr + extent_offset;
+ search_len = extent_num_bytes;
+ } else {
+ search_start = disk_bytenr;
+ search_len = disk_num_bytes;
+ }
+ ret = count_csum_range(root, search_start, search_len, &csum_found);
+ if (csum_found > 0 && nodatasum) {