mkdosfs incorrectly calculates sector total

Binary package hint: dosfstools

mkdosfs will incorrectly calculate the number of sectors of a given FAT partition if the number sectors are odd due to count_blocks incorrectly handling the remainder of a division operation. This miscalculation causes the OMAP4 bootloader to fail to boot.

This bug can be observed by comparing the total sector size in fdisk expert more to fsck.msdos; this discrepancy only shows up when the number of sectors are odd:

fdisk output:

Expert command (m for help): p

Disk /dev/sdb: 204 heads, 3 sectors, 12654 cylinders

Nr AF Hd Sec Cyl Hd Sec Cyl Start Size ID
 1 00 1 1 0 203 3 258 3 158505 83
 2 00 0 0 0 0 0 0 0 0 00
 3 00 0 0 0 0 0 0 0 0 00
 4 00 0 0 0 0 0 0 0 0 00

mcasadevall@daybreak:~/src/dosfstools-3.0.9$ sudo fsck.msdos -v /dev/sdb1
dosfsck 3.0.9 (31 Jan 2010)
dosfsck 3.0.9, 31 Jan 2010, FAT32, LFN
Checking we can access the last sector of the filesystem
Boot sector contents:
System ID "mkdosfs"
Media byte 0xf8 (hard disk)
       512 bytes per logical sector
      2048 bytes per cluster
         4 reserved sectors
First FAT starts at byte 2048 (sector 4)
         2 FATs, 16 bit entries
     79872 bytes per FAT (= 156 sectors)
Root directory starts at byte 161792 (sector 316)
       512 root directory entries
Data area starts at byte 178176 (sector 348)
     39539 data clusters (80975872 bytes)
3 sectors/track, 204 heads
         0 hidden sectors
    158504 sectors total
Checking for unused clusters.
/dev/sdb1: 0 files, 0/39539 clusters

Compare the difference in sectors total. The attached patch correctly handles the remainder and causes the sector counts to match.