Re: [Qemu-devel] [PATCH 2/2] ISCSI: Force scsi-generic for MMC with blank disks

[ronnie sahlberg]

Ah,

This patch only affects the case when there is a blank / empty disk loaded.
It has no effect on when real *.iso images are loaded and the disk
contains data.

The use case to be able to "burn" to an iscsi cdrom is probably not
very urgent, so maybe it is best to delay this until post 1.2


regards
ronnie sahlberg


On Sun, Aug 19, 2012 at 8:02 AM, ronnie sahlberg
<address@hidden> wrote:
> On Sun, Aug 19, 2012 at 7:58 AM, Paolo Bonzini <address@hidden> wrote:
>> Il 17/08/2012 04:36, Ronnie Sahlberg ha scritto:
>>> There is no bdrv_* API for the commands for burning a blank MMC disk
>>> so when iSCSI LUNs are specified and the LUN is a MMC device with
>>> 0 available blocks. This is a blank disk so force scsi generic.
>>>
>>> This allows the guest to talk directly to the target to burn data on
>>> the disk.
>>>
>>> Signed-off-by: Ronnie Sahlberg <address@hidden>
>>
>> What happens without the patch?  It's ok that scsi-{hd,cd} does not
>> work, but do scsi-{block,generic} work without the patch?
>>
>
> Neither of them work, basically because in
> block.c:find_image_format()
>
> if bs->sg is not set in
>
>  if (bs->sg || !bdrv_is_inserted(bs)) {
>
> then we continue to
>
>   ret = bdrv_pread(bs, 0, buf, sizeof(buf));
>
> which fails with an error.
> So this patch is basically to prevent find_image_format() from trying
> to read from a blank disk.
>
> Maybe there is a better way to do this?
>
>
>
> regards
> ronnie sahlberg