Re: [Qemu-devel] [PATCH] Chage disk serial length from 20 to 36

[Markus Armbruster <armbru@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 30/08/2016 14:08, Markus Armbruster wrote:
>> Paolo Bonzini <pbonzini@redhat.com> writes:
>> 
>>> On 29/08/2016 09:52, ronyweng@synology.com wrote:
>>>> From: ronyweng <ronyweng@synology.com>
>>>>
>>>> Openstack Cinder assigns volume a 36 characters uuid as serial.
>>>> Qemu will shrinks the uuid to 20 characters,
>>>> missmatch with original uuid.
>>>>
>>>> Signed-off-by: Rony Weng <ronyweng@synology.com>
>>>> ---
>>>>  hw/scsi/scsi-disk.c | 4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
>>>> index 836a155..0e1bb68 100644
>>>> --- a/hw/scsi/scsi-disk.c
>>>> +++ b/hw/scsi/scsi-disk.c
>>>> @@ -599,8 +599,8 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, uint8_t *outbuf)
>>>>              }
>>>>  
>>>>              l = strlen(s->serial);
>>>> -            if (l > 20) {
>>>> -                l = 20;
>>>> +            if (l > 36) {
>>>> +                l = 36;
>>>>              }
>>>>  
>>>>              DPRINTF("Inquiry EVPD[Serial number] "
>>>>
>>>
>>> Cc: qemu-stable@nongnu.org
>>>
>>> Thanks, queued for 2.8 and 2.7.1
>>>
>>> Paolo
>> 
>> Pointing to the applicable SCSI spec chapter & verse in the commit
>> message would be nice.  As is, 36 looks as arbitrary as 20.
>
> There is no limit in the SCSI spec.  20 was copy-pasted from virtio-blk
> which in turn was copy-pasted from ATA.  So 36 is even more arbitrary,
> but bumping it up too much might cause issues (e.g. who knows there's no
> off-by-one somewhere if I make it 252, so that 256 is the maximum amount
> of returned data).

This paragraph would make a nice addition to the commit message :)