qemu: process: Extract host setup of disk device into helpers

Currently the code sets up only VDPA backends but will be used later in
hotplug code too.

This patch also uses normal forward iteration in the loop in
qemuProcessPrepareHostStorage as we don't need to remove disks from the
disk list at that point.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/qemu/qemu_process.c

@@ -6777,6 +6777,69 @@ qemuProcessPrepareHostStorageSourceVDPA(virStorageSource *src,
 }
 
 
+/**
+ * See qemuProcessPrepareHostStorageSourceChain
+ */
+int
+qemuProcessPrepareHostStorageSource(virDomainObj *vm,
+                                    virStorageSource *src)
+{
+    /* connect to any necessary vdpa block devices */
+    if (qemuProcessPrepareHostStorageSourceVDPA(src, vm->privateData) < 0)
+        return -1;
+
+    return 0;
+}
+
+
+/**
+ * qemuProcessPrepareHostStorageSourceChain:
+ *
+ * @vm: domain object
+ * @chain: source chain
+ *
+ * Prepare the host side of a disk for use with the VM. Note that this function
+ * accesses host resources.
+ */
+int
+qemuProcessPrepareHostStorageSourceChain(virDomainObj *vm,
+                                         virStorageSource *chain)
+{
+    virStorageSource *n;
+
+    for (n = chain; virStorageSourceIsBacking(n); n = n->backingStore) {
+        if (qemuProcessPrepareHostStorageSource(vm, n) < 0)
+            return -1;
+    }
+
+    return 0;
+}
+
+
+/**
+ * qemuProcessPrepareHostStorageDisk:
+ *
+ * @vm: domain object
+ * @disk: disk definition object
+ *
+ * Prepare the host side of a disk for use with the VM. Note that this function
+ * accesses host resources.
+ *
+ * Note that this function does not call qemuDomainDetermineDiskChain as that is
+ * needed in qemuProcessPrepareHostStorage to remove disks based on the startup
+ * policy, thus other callers need to call it explicitly.
+ */
+int
+qemuProcessPrepareHostStorageDisk(virDomainObj *vm,
+                                  virDomainDiskDef *disk)
+{
+    if (qemuProcessPrepareHostStorageSourceChain(vm, disk->src) < 0)
+        return -1;
+
+    return 0;
+}
+
+
 static int
 qemuProcessPrepareHostStorage(virQEMUDriver *driver,
                               virDomainObj *vm,
@@ -6813,16 +6876,11 @@ qemuProcessPrepareHostStorage(virQEMUDriver *driver,
         return -1;
     }
 
-    /* connect to any necessary vdpa block devices */
-    for (i = vm->def->ndisks; i > 0; i--) {
-        size_t idx = i - 1;
-        virDomainDiskDef *disk = vm->def->disks[idx];
-        virStorageSource *src;
+    for (i = 0; i < vm->def->ndisks; i++) {
+        virDomainDiskDef *disk = vm->def->disks[i];
 
-        for (src = disk->src; virStorageSourceIsBacking(src); src = src->backingStore) {
-            if (qemuProcessPrepareHostStorageSourceVDPA(src, vm->privateData) < 0)
-                return -1;
-        }
+        if (qemuProcessPrepareHostStorageDisk(vm, disk) < 0)
+            return -1;
     }
 
     return 0;

src/qemu/qemu_process.h

@@ -133,6 +133,13 @@ int qemuProcessPrepareHost(virQEMUDriver *driver,
                            virDomainObj *vm,
                            unsigned int flags);
 
+int qemuProcessPrepareHostStorageSource(virDomainObj *vm,
+                                        virStorageSource *src);
+int qemuProcessPrepareHostStorageSourceChain(virDomainObj *vm,
+                                             virStorageSource *chain);
+int qemuProcessPrepareHostStorageDisk(virDomainObj *vm,
+                                  virDomainDiskDef *disk);
+
 int qemuProcessDeleteThreadContext(virDomainObj *vm);
 
 int qemuProcessLaunch(virConnectPtr conn,