Kevin Wolf <kw...@redhat.com> writes: > Am 05.07.2012 11:23, schrieb Markus Armbruster: >> Kevin Wolf <kw...@redhat.com> writes: >> >>> Am 29.06.2012 22:33, schrieb Blue Swirl: >>>> On Fri, Jun 29, 2012 at 3:34 PM, Markus Armbruster <arm...@redhat.com> >>>> wrote: >>>>> 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 <arm...@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..62745b5 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); >>>> >>>> Spaces around '-'. Thanks for fixing the other cases, BTW. >>> >>> For compensation there's an extra space before the '='. >> >> The original lined up the two '='. I preserved that. Not that I care >> for it. Want me to drop the extra space? > > Ah, didn't notice that. I don't mind then. > >>>>> + partition->length_sector_long = cpu_to_le32(s->bs->total_sectors >>>>> + - >>>>> s->first_sectors_number + 1); >>> >>> Just wondering... This should be the same as s->sector_count, right? >> >> Hmm. vvfat_open() assigns: >> >> s->sector_count = cyls * heads * secs - (s->first_sectors_number - 1); >> bs->total_sectors = cyls * heads * secs; >> >> But it then changes it minds and does: >> >> s->sector_count = s->faked_sectors + >> s->sectors_per_cluster*s->cluster_count; > > Which probably means that they differ if some sub-cluster sized space is > left unused at the end of the disk. It's not useful to have this space > included in the partition, but it doesn't hurt either. So I suppose > either way is fine.
Complication: the partition should end on a cylinder boundary. Shaving off an unused tail may well interfere with that. Let's stick to v1 here. [...]
