On Mon, Nov 09, 2009 at 02:08:27PM +0100, Karel Zak wrote:
> On Fri, Oct 23, 2009 at 12:36:15PM +0200, Karel Zak wrote:
> > Currently, kernel uses strictly 512-byte sectors for EFI GPT parsing.
> > That's wrong.
>
> Ping? Does anyone care about new disks with non-512byte sectors?
> (or fs/partitions is unmaintained area? ;-)
[as you must have noticed, I hardly do any kernel work any more;
probably there aren't many who know more about the ugly details
of DOS-type partition tables, but on the other hand nobody needs
such knowledge either]
> The current kernel EFI GPT code in not compatible with the latest
> userspace and GPT partitions on disks with >512byte sectors will be
> *invisible* for Linux kernel.
Yes, I see that the current UEFI standard requires the use of the
disks block size. Roughly speaking I agree with your patch.
(Just read some current kernel code. The old hardsect_size stuff was
renamed to logical_block_size - funny, originally that was precisely
what hardsect was not.)
static size_t
read_lba(struct block_device *bdev, u64 lba, u8 * buffer, size_t count)
{
size_t totalreadcount = 0;
sector_t n = lba * (bdev_logical_block_size(bdev) / 512);
if (!bdev || !buffer || lba > last_lba(bdev))
return 0;
while (count) {
int copied = 512;
Sector sect;
unsigned char *data = read_dev_sector(bdev, n++, §);
if (!data)
break;
if (copied > count)
copied = count;
memcpy(buffer, data, copied);
put_dev_sector(sect);
buffer += copied;
totalreadcount +=copied;
count -= copied;
}
return totalreadcount;
}
Ugly - it looks as if you call read_dev_sector 8 times and each time
do a put_dev_sector afterwards to forget it again. Doesnt that mean
that in order to read a 4096-byte sector the kernel goes to the hardware
8 times?
Andries
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