On Fri, Jan 30, 2009 at 11:54:02AM +0200, Timo Juhani Lindfors wrote:
> Package: nbd-server
> Version: 1:2.9.11-2
> Severity: normal
>
> Steps to reproduce:
> 0) make sure /dev/md0 has size of 3000614518784 bytes
Eh. Hrm. Got some spare disks? ;-)
(nvm, I can use sparse files :-)
> 1) nbd-server 2000 /dev/md0
> 2) nc localhost 2000 | hexdump -C
>
> Expected results:
> 2) netcat shows the NBD init packet, second row starts with
> 0x000002baa2900000 as this is the size of the device in hex.
>
> Actual results:
> 2) netcat shows the NBD init packet, second row starts with
> 0x000000baa2900000 which is NOT the size of the block device.
>
> 00000000 4e 42 44 4d 41 47 49 43 00 00 42 02 81 86 12 53 |NBDMAGIC..B....S|
> 00000010 00 00 00 ba a2 90 00 00 00 00 00 01 00 00 00 00 |................|
>
> It seems that nbd-server is for some reason zeroing the upper three
> bytes of the size field and preventing the use of such large devices.
Hrm. Not good.
> More info:
> 1) nbd-server logs
>
> Jan 30 11:36:09 nbd_server[6740]: Size of exported file/device is 801591263232
>
> which is 0x000000baa2900000 in hex and incorrect.
>
> 2) It seems that the kernel API returns 'unsigned long' count of
> 512-byte sectors. On this 32-bit system 'unsigned long' is 4 bytes so
> this interface is not sufficient to support 3TB:
>
> off_t size_autodetect(int fhandle) {
> off_t es;
> unsigned long sectors;
> struct stat stat_buf;
> int error;
>
> #ifdef HAVE_SYS_MOUNT_H
> #ifdef HAVE_SYS_IOCTL_H
> #ifdef BLKGETSIZE
> DEBUG("looking for export size with ioctl BLKGETSIZE\n");
> if (!ioctl(fhandle, BLKGETSIZE, §ors) && sectors) {
> es = (off_t)sectors * (off_t)512;
I'm open to suggestions for another API to use. In the mean time,
specifying the device size manually should work...
> 3) In addition, off_t is also only 4 bytes so even if I manually
> specify the right size of the block device I still get wrong size back:
>
> $ nbd-server 2000 /dev/md0 3000614518784
> $ nc localhost 2000|hexdump -C
> 00000000 4e 42 44 4d 41 47 49 43 00 00 42 02 81 86 12 53 |NBDMAGIC..B....S|
> 00000010 00 00 00 ba a2 90 00 00 00 00 00 01 00 00 00 00 |................|
... except it doesn't.
Not for the reasons you claim, though -- nbd-server is compiled with
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_ITS=64, so off_t should be an 8-byte
integer, not a 4-byte one.
I'll try to debug this ASAP, but help is of course always welcome.
As a workaround, you should be able to use the "multiple file" option --
though I guess that might be quite hard if sharing the individual block
devices that make up md0 is not an option. I also haven't tried that
with 3TB files, however...
--
<Lo-lan-do> Home is where you have to wash the dishes.
-- #debian-devel, Freenode, 2004-09-22
--
To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org
with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
