qemu: refactor qemuDomainCheckDiskPresence for only disk presence check

Refactor this function to make it focus on disk presence checking,
including diskchain checking, and not only for CDROM and Floppy.
This change is good for the following patches.

src/qemu/qemu_domain.c

@@ -2026,6 +2026,61 @@ cleanup:
     virObjectUnref(cfg);
 }
 
+static int
+qemuDomainCheckDiskStartupPolicy(virQEMUDriverPtr driver,
+                                 virDomainObjPtr vm,
+                                 virDomainDiskDefPtr disk,
+                                 bool cold_boot)
+{
+    char uuid[VIR_UUID_STRING_BUFLEN];
+    virDomainEventPtr event = NULL;
+    int startupPolicy = disk->startupPolicy;
+
+    virUUIDFormat(vm->def->uuid, uuid);
+
+    switch ((enum virDomainStartupPolicy) startupPolicy) {
+        case VIR_DOMAIN_STARTUP_POLICY_OPTIONAL:
+            break;
+
+        case VIR_DOMAIN_STARTUP_POLICY_MANDATORY:
+            virReportSystemError(errno,
+                                 _("cannot access file '%s'"),
+                                 disk->src);
+            goto error;
+            break;
+
+        case VIR_DOMAIN_STARTUP_POLICY_REQUISITE:
+            if (cold_boot) {
+                virReportSystemError(errno,
+                                     _("cannot access file '%s'"),
+                                     disk->src);
+                goto error;
+            }
+            break;
+
+        case VIR_DOMAIN_STARTUP_POLICY_DEFAULT:
+        case VIR_DOMAIN_STARTUP_POLICY_LAST:
+            /* this should never happen */
+            break;
+    }
+
+    VIR_DEBUG("Dropping disk '%s' on domain '%s' (UUID '%s') "
+              "due to inaccessible source '%s'",
+              disk->dst, vm->def->name, uuid, disk->src);
+
+    event = virDomainEventDiskChangeNewFromObj(vm, disk->src, NULL, disk->info.alias,
+                                               VIR_DOMAIN_EVENT_DISK_CHANGE_MISSING_ON_START);
+    if (event)
+        qemuDomainEventQueue(driver, event);
+
+    VIR_FREE(disk->src);
+
+    return 0;
+
+error:
+    return -1;
+}
+
 int
 qemuDomainCheckDiskPresence(virQEMUDriverPtr driver,
                             virDomainObjPtr vm,
@@ -2034,12 +2089,8 @@ qemuDomainCheckDiskPresence(virQEMUDriverPtr driver,
     int ret = -1;
     size_t i;
     virDomainDiskDefPtr disk;
-    char uuid[VIR_UUID_STRING_BUFLEN];
-    virDomainEventPtr event = NULL;
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
 
-    virUUIDFormat(vm->def->uuid, uuid);
-
     for (i = 0; i < vm->def->ndisks; i++) {
         disk = vm->def->disks[i];
 
@@ -2053,42 +2104,9 @@ qemuDomainCheckDiskPresence(virQEMUDriverPtr driver,
             continue;
         }
 
-        switch ((enum virDomainStartupPolicy) disk->startupPolicy) {
-            case VIR_DOMAIN_STARTUP_POLICY_OPTIONAL:
-                break;
-
-            case VIR_DOMAIN_STARTUP_POLICY_MANDATORY:
-                virReportSystemError(errno,
-                                     _("cannot access file '%s'"),
-                                     disk->src);
-                goto cleanup;
-                break;
-
-            case VIR_DOMAIN_STARTUP_POLICY_REQUISITE:
-                if (cold_boot) {
-                    virReportSystemError(errno,
-                                         _("cannot access file '%s'"),
-                                         disk->src);
-                    goto cleanup;
-                }
-                break;
-
-            case VIR_DOMAIN_STARTUP_POLICY_DEFAULT:
-            case VIR_DOMAIN_STARTUP_POLICY_LAST:
-                /* this should never happen */
-                break;
-        }
-
-        VIR_DEBUG("Dropping disk '%s' on domain '%s' (UUID '%s') "
-                  "due to inaccessible source '%s'",
-                  disk->dst, vm->def->name, uuid, disk->src);
-
-        event = virDomainEventDiskChangeNewFromObj(vm, disk->src, NULL, disk->info.alias,
-                                                   VIR_DOMAIN_EVENT_DISK_CHANGE_MISSING_ON_START);
-        if (event)
-            qemuDomainEventQueue(driver, event);
-
-        VIR_FREE(disk->src);
+        if (qemuDomainCheckDiskStartupPolicy(driver, vm, disk,
+                                             cold_boot) < 0)
+            goto cleanup;
     }
 
     ret = 0;