[libvirt] [PATCH 4/4] conf: Fix generating addresses for SCSI hostdev

[John Ferlan]

On 12/20/2017 07:38 AM, Ján Tomko wrote:
> On Wed, Dec 06, 2017 at 08:08:06AM -0500, John Ferlan wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1519130
>>
>> Commit id 'dc692438' reverted the automagic addition of a SCSI
>> controller attempt during virDomainHostdevAssignAddress; however,
>> the logic to determine where to place the next_unit depended upon
>> the "new" controller being added.  Without the new controller the
>> the next time through the call for the next SCSI hostdev found
>> would result in the "next_unit" never changing from 0 (zero) and
>> as a result the addition of the device will fail due to being a
>> duplicate unit number of the first with the error message:
>>
>>  virDomainDefCheckDuplicateDriveAddresses:$line : unsupported
>>      configuration: SCSI host address controller='0' bus='1'
>>      target='0' unit='0' in use by another SCSI host device
>>
>> So instead of walking the controller list looking for SCSI
>> controllers, all we can do is "pretend" that they exist and
>> allow other code to create them later as necessary.
>>
>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>> ---
>> src/conf/domain_conf.c | 31 +++++++++++++------------------
>> 1 file changed, 13 insertions(+), 18 deletions(-)
>>
>> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>> index 61b4a0075..73c6708cf 100644
>> --- a/src/conf/domain_conf.c
>> +++ b/src/conf/domain_conf.c
>> @@ -4322,10 +4322,8 @@
>> virDomainHostdevAssignAddress(virDomainXMLOptionPtr xmlopt,
>>                               const virDomainDef *def,
>>                               virDomainHostdevDefPtr hostdev)
>> {
>> -    int next_unit = 0;
> 
> Please keep the descriptive 'next_unit' variable name.
> 
>> -    unsigned controller = 0;
>> +    int controller = 0;
>>     unsigned int max_unit;
>> -    size_t i;
>>     int ret;
>>
>>     if (xmlopt->config.features & VIR_DOMAIN_DEF_FEATURE_WIDE_SCSI)
>> @@ -4333,33 +4331,30 @@
>> virDomainHostdevAssignAddress(virDomainXMLOptionPtr xmlopt,
>>     else
>>         max_unit = SCSI_NARROW_BUS_MAX_CONT_UNIT;
>>
>> -    for (i = 0; i < def->ncontrollers; i++) {
>> -        if (def->controllers[i]->type !=
>> VIR_DOMAIN_CONTROLLER_TYPE_SCSI)
>> -            continue;
>> -
>> -        controller++;
>> -        ret = virDomainControllerSCSINextUnit(def, max_unit,
>> -                                              def->controllers[i]->idx);
>> -        if (ret >= 0) {
>> -            next_unit = ret;
>> -            controller = def->controllers[i]->idx;
>> -            break;
>> -        }
>> -    }
>> -
>>     /* NB: Do not attempt calling virDomainDefMaybeAddController to
>>      * automagically add a "new" controller. Doing so will result in
>>      * qemuDomainFindOrCreateSCSIDiskController "finding" the controller
>>      * in the domain def list and thus not hotplugging the controller as
>>      * well as the hostdev in the event that there are either no SCSI
>>      * controllers defined or there was no space on an existing one.
>> +     *
>> +     * Because we cannot add a controller, then we should not walk the
>> +     * defined controllers list in order to find empty space. Doing
>> +     * so fails to return the valid next unit number for the 2nd
>> +     * hostdev being added to the as yet to be created controller.
>>      */
>> +    do {
>> +        ret = virDomainControllerSCSINextUnit(def, max_unit,
>> controller);
>> +        if (ret < 0)
>> +            controller++;
>> +    } while (ret < 0);
>> +
> 
> Easier to read as:
> for (next_unit = -1; next_unit < -1; controller++)
>    next_unit = virDomainControllerSCSINextUnit(def, max_unit, controller);
> 

Not functionally the same comparisons... Caused
hostdev-scsi-autogen-address to fail... There's 11 hostdevs and only 1
controller. We never get controller==1 from that for loop.

I can change @ret above to be @next_unit though


John

> ACK
> 
> Jan
>>
>>     hostdev->info->type = VIR_DOMAIN_DEVICE_ADDRESS_TYPE_DRIVE;
>>     hostdev->info->addr.drive.controller = controller;
>>     hostdev->info->addr.drive.bus = 0;
>>     hostdev->info->addr.drive.target = 0;
>> -    hostdev->info->addr.drive.unit = next_unit;
>> +    hostdev->info->addr.drive.unit = ret;
>>
>>     return 0;
>> }
>> -- 
>> 2.13.6
>>
>> -- 
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