[Qemu-devel] [PATCH 04/41] vvfat: Fix partition table

[Kevin Wolf <kwolf@redhat.com>]

From: Markus Armbruster <armbru@redhat.com>

Unless parameter ":floppy:" is given, vvfat creates a virtual image
with DOS MBR defining a single partition which holds the FAT file
system.  The size of the virtual image depends on the width of the
FAT: 32 MiB (CHS 64, 16, 63) for 12 bit FAT, 504 MiB (CHS 1024, 16,
63) for 16 and 32 bit FAT, leaving (64*16-1)*63 = 64449 and
(1024*16-1)*64 = 1032129 sectors for the partition.

However, it screws up the end of the partition in the MBR:

    FAT width param.  start CHS  end CHS     start LBA  size
        :32:          0,1,1      1023,14,63       63    1032065
        :16:          0,1,1      1023,14,55       63    1032057
        :12:          0,1,1        63,14,55       63      64377

The actual FAT file system nevertheless assumes the partition has
1032129 or 64449 sectors.  Oops.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/vvfat.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/block/vvfat.c b/block/vvfat.c
index 0fd3367..e2b83a2 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -394,11 +394,12 @@ static void init_mbr(BDRVVVFATState* s)
 
     /* LBA is used when partition is outside the CHS geometry */
     lba = sector2CHS(s->bs, &partition->start_CHS, s->first_sectors_number-1);
-    lba|= sector2CHS(s->bs, &partition->end_CHS,   s->sector_count);
+    lba |= sector2CHS(s->bs, &partition->end_CHS, s->bs->total_sectors - 1);
 
     /*LBA partitions are identified only by start/length_sector_long not by CHS*/
-    partition->start_sector_long =cpu_to_le32(s->first_sectors_number-1);
-    partition->length_sector_long=cpu_to_le32(s->sector_count - s->first_sectors_number+1);
+    partition->start_sector_long  = cpu_to_le32(s->first_sectors_number - 1);
+    partition->length_sector_long = cpu_to_le32(s->bs->total_sectors
+                                                - s->first_sectors_number + 1);
 
     /* FAT12/FAT16/FAT32 */
     /* DOS uses different types when partition is LBA,
-- 
1.7.6.5