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

[John Ferlan]

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;
-    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);
+
 
     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