+static ssize_t find_good_sector(secaddr *pos_inout, secaddr end,
+ unsigned char *buf, secaddr sz)
+{
+ int i;
+ secaddr pos = *pos_inout, bad_lo, bad_hi, good, step;
+ ssize_t n;
+
+ report_bad_blocks_progress(pos, pos, errno);
+ for (i = 0; i < 4; i++) {
+ n = read_sectors(pos, buf, 1);
+ if (n > 0) {
+ clear_progress();
+ moan("sector %"PRIuSEC" read ok after retry", pos);
+ bad_lo = bad_hi = pos;
+ goto recovered;
+ }
+ }
+
+ bad_lo = pos; step = 1; bad_hi = pos + 1;
+ for (;;) {
+ report_bad_blocks_progress(bad_lo, bad_hi, errno);
+ if (bad_hi >= end) {
+ clear_progress();
+ moan("giving up on this extent");
+ n = 0; goto recovered;
+ }
+ step *= 2;
+ if (step > end - bad_lo) step = end - bad_lo;
+ pos = bad_lo + step - 1;
+ n = read_sectors(pos, buf, 1);
+ if (n > 0) break;
+ bad_hi = pos + 1;
+ }
+
+ good = pos;
+ while (good > bad_hi) {
+ report_bad_blocks_progress(bad_lo, bad_hi, errno);
+ pos = bad_hi + (good - bad_hi)/2;
+ n = read_sectors(pos, buf, 1);
+ if (n > 0) good = pos;
+ else bad_hi = pos + 1;
+ }
+recovered:
+ if (bad_hi > bad_lo) {
+ clear_progress();
+ moan("skipping %"PRIuSEC" bad sectors (%"PRIuSEC" .. %"PRIuSEC")",
+ bad_hi - bad_lo, bad_lo, bad_hi);
+ if (mapfile) {
+ if (!mapfp) {
+ mapfp = fopen(mapfile, "w");
+ if (!mapfp)
+ bail_syserr(errno, "failed to open bad-sector map file `%s'",
+ optarg);
+ fprintf(mapfp, "## bad sector map\n\n");
+ }
+ fprintf(mapfp, "%"PRIuSEC" %"PRIuSEC"\n", bad_lo, bad_hi);
+ fflush(mapfp);
+ if (ferror(mapfp))
+ bail_syserr(errno, "error writing bad-sector map file");
+ }
+ if (lseek(outfd, (off_t)(bad_hi - bad_lo)*SECTORSZ, SEEK_CUR) < 0)
+ bail_syserr(errno, "failed to seek past bad sectors");
+ status = 1;
+ }
+ *pos_inout = bad_hi;
+ return (n);
+}
+