qemu: block: Use qemuBlockStorageSourceNeedsStorageSliceLayer only for setup

Add a note stating that qemuBlockStorageSourceNeedsStorageSliceLayer
must be used only when setting up a new blockdev, any other case when
the device might been already set up must use the existence of the
nodename to do so.

Adjust qemuBlockStorageSourceAttachPrepareBlockdev to do so and refactor
qemuBlockStorageSourceDetachPrepare to use the same logic.

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

diff --git a/src/qemu/qemu_block.c b/src/qemu/qemu_block.c
index 1d0361b05e78c07273adba2183c05c8a77feb354..14c020894fa2f83cc72aad4f52527dd312ecbf10 100644 (file)
--- a/src/qemu/qemu_block.c
+++ b/src/qemu/qemu_block.c
@@ -1535,11 +1535,9 @@ qemuBlockStorageSourceAttachPrepareBlockdev(virStorageSource *src,
     data->storageNodeName = qemuBlockStorageSourceGetStorageNodename(src);
     data->formatNodeName = qemuBlockStorageSourceGetFormatNodename(src);
 
-    if (qemuBlockStorageSourceNeedsStorageSliceLayer(src)) {
+    if ((data->storageSliceNodeName = qemuBlockStorageSourceGetSliceNodename(src))) {
         if (!(data->storageSliceProps = qemuBlockStorageSourceGetBlockdevStorageSliceProps(src)))
             return NULL;
-
-        data->storageSliceNodeName = src->sliceStorage->nodename;
     }
 
     return g_steal_pointer(&data);
@@ -1756,13 +1754,8 @@ qemuBlockStorageSourceDetachPrepare(virStorageSource *src)
     data->storageNodeName = qemuBlockStorageSourceGetStorageNodename(src);
     data->storageAttached = true;
 
-    /* 'raw' format doesn't need the extra 'raw' layer when slicing, thus
-     * the nodename is NULL */
-    if (src->sliceStorage &&
-        src->sliceStorage->nodename) {
-        data->storageSliceNodeName = src->sliceStorage->nodename;
+    if ((data->storageSliceNodeName = qemuBlockStorageSourceGetSliceNodename(src)))
         data->storageSliceAttached = true;
-    }
 
     if (src->pr &&
         !virStoragePRDefIsManaged(src->pr))
@@ -3274,6 +3267,12 @@ qemuBlockReopenReadOnly(virDomainObj *vm,
  *
  * Returns true if @src requires an extra 'raw' layer for handling of the storage
  * slice.
+ *
+ * Important: This helper must be used only for decisions when setting up a
+ * '-blockdev' backend in which case the storage slice layer node name will be
+ * populated.
+ * Any cases when the backend can be already in use must decide based on the
+ * existence of the storage slice layer nodename.
  */
 bool
 qemuBlockStorageSourceNeedsStorageSliceLayer(const virStorageSource *src)