Messages in this thread | | | Date | Mon, 9 Nov 2009 20:58:32 +0100 | From | "Andries E. Brouwer" <> | Subject | Re: [PATCH 1/2] partitions: use sector size for EFI GPT |
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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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