Re: [Qemu-devel] [PATCH 7/8] iscsi: assert that sectors are aligned to LUN blocksize

[Peter Lieven]

Am 24.06.2013 18:13, schrieb Paolo Bonzini:
> Il 24/06/2013 18:10, Peter Lieven ha scritto:
>> Am 24.06.2013 16:30, schrieb Paolo Bonzini:
>>> Il 22/06/2013 22:58, Peter Lieven ha scritto:
>>>> if the blocksize of an iSCSI LUN is bigger than the BDRV_SECTOR_SIZE
>>>> it is possible that sector_num or nb_sectors are not correctly
>>>> alligned.
>>>>
>>>> for now assert that there is no misalignment to avoid data
>>>> corruption.
>>> You should just fail to open the LUN instead.
>> Ronnie added support for reading fragments of blocksize if the
>> offset is aligned. I don't know what the idea was, maybe for qemu
>> reading the boot sector. If the OS does only read multiple of
>> blocksize at aligned offsets everything should work. I now that
>> our storages support 4K blocksize. I can check if it is usable.
>> I could also just fail the operations instead of asserting.
> So far, 4K blocksize is usable if you also specify the same block size
> for the guest device.  I have posted once the patches to do
> read-modify-write, but I never really pursued inclusion of those.
>
> In any case, the right place to fix this is the block layer;
> driver-specific hacks are... hacks. :)
Where do I find the sector size if not in BDRV_SECTOR_SIZE?
Is there a dynamic field or is the answer qemu only support 512 Byte
sector size at the moment?

So you would go for fail to open a device if the LUN blocksize is
not equal to BDRV_SECTOR_SIZE?

Peter