qemu: checkpoint: Track and relabel images for bitmap merging

Allow qemu access to modify backing files in case when we want to delete
a checkpoint.

This patch adds tracking of which images need to be relabelled when
calculating the transaction, the code to relabel them and rollback.

To verify that stuff works we also output the list of images to relabel
into the test case output files in qemublocktest.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/qemu/qemu_checkpoint.c

@@ -155,7 +155,8 @@ qemuCheckpointDiscardDiskBitmaps(virStorageSourcePtr src,
                                  const char *delbitmap,
                                  const char *parentbitmap,
                                  virJSONValuePtr actions,
-                                 const char *diskdst)
+                                 const char *diskdst,
+                                 GSList **reopenimages)
 {
     virStorageSourcePtr n = src;
 
@@ -235,6 +236,9 @@ qemuCheckpointDiscardDiskBitmaps(virStorageSourcePtr src,
                                                srcbitmap->name) < 0)
             return -1;
 
+        if (n != src)
+            *reopenimages = g_slist_prepend(*reopenimages, n);
+
         n = n->backingStore;
     }
 
@@ -250,9 +254,12 @@ qemuCheckpointDiscardBitmaps(virDomainObjPtr vm,
     qemuDomainObjPrivatePtr priv = vm->privateData;
     virQEMUDriverPtr driver = priv->driver;
     g_autoptr(virHashTable) blockNamedNodeData = NULL;
-    int rc;
+    int rc = -1;
     g_autoptr(virJSONValue) actions = NULL;
     size_t i;
+    g_autoptr(GSList) reopenimages = NULL;
+    g_autoptr(GSList) relabelimages = NULL;
+    GSList *next;
 
     if (!(actions = virJSONValueNewArray()))
         return -1;
@@ -284,16 +291,34 @@ qemuCheckpointDiscardBitmaps(virDomainObjPtr vm,
 
         if (qemuCheckpointDiscardDiskBitmaps(domdisk->src, blockNamedNodeData,
                                              chkdisk->bitmap, parentbitmap,
-                                             actions, domdisk->dst) < 0)
+                                             actions, domdisk->dst,
+                                             &reopenimages) < 0)
             return -1;
     }
 
+    /* label any non-top images for read-write access */
+    for (next = reopenimages; next; next = next->next) {
+        virStorageSourcePtr src = next->data;
+
+        if (qemuDomainStorageSourceAccessAllow(driver, vm, src, false, false) < 0)
+            goto relabel;
+
+        relabelimages = g_slist_prepend(relabelimages, src);
+    }
+
     qemuDomainObjEnterMonitor(driver, vm);
     rc = qemuMonitorTransaction(priv->mon, &actions);
-    if (qemuDomainObjExitMonitor(driver, vm) < 0 || rc < 0)
+    if (qemuDomainObjExitMonitor(driver, vm) < 0)
         return -1;
 
-    return 0;
+ relabel:
+    for (next = relabelimages; next; next = next->next) {
+        virStorageSourcePtr src = next->data;
+
+        ignore_value(qemuDomainStorageSourceAccessAllow(driver, vm, src, true, false));
+    }
+
+    return rc;
 }
 
 

src/qemu/qemu_checkpoint.h

@@ -78,4 +78,5 @@ qemuCheckpointDiscardDiskBitmaps(virStorageSourcePtr src,
                                  const char *delbitmap,
                                  const char *parentbitmap,
                                  virJSONValuePtr actions,
-                                 const char *diskdst);
+                                 const char *diskdst,
+                                 GSList **reopenimages);

tests/qemublocktest.c

@@ -721,6 +721,9 @@ testQemuCheckpointDeleteMerge(const void *opaque)
     g_autoptr(virJSONValue) actions = NULL;
     g_autoptr(virJSONValue) nodedatajson = NULL;
     g_autoptr(virHashTable) nodedata = NULL;
+    g_autoptr(GSList) reopenimages = NULL;
+    g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
+    GSList *tmp;
 
     expectpath = g_strdup_printf("%s/%s%s-out.json", abs_srcdir,
                                  checkpointDeletePrefix, data->name);
@@ -742,14 +745,26 @@ testQemuCheckpointDeleteMerge(const void *opaque)
                                          data->deletebitmap,
                                          data->parentbitmap,
                                          actions,
-                                         "testdisk") < 0) {
+                                         "testdisk",
+                                         &reopenimages) < 0) {
         VIR_TEST_VERBOSE("failed to generate checkpoint delete transaction\n");
         return -1;
     }
 
-    if (!(actual = virJSONValueToString(actions, true)))
+    if (virJSONValueToBuffer(actions, &buf, true) < 0)
         return -1;
 
+    if (reopenimages) {
+        virBufferAddLit(&buf, "reopen nodes:\n");
+
+        for (tmp = reopenimages; tmp; tmp = tmp->next) {
+            virStorageSourcePtr src = tmp->data;
+            virBufferAsprintf(&buf, "%s\n", src->nodeformat);
+        }
+    }
+
+    actual = virBufferContentAndReset(&buf);
+
     return virTestCompareToFile(actual, expectpath);
 }
 

tests/qemublocktestdata/checkpointdelete/snapshots-intermediate1-out.json

@@ -20,3 +20,5 @@
     }
   }
 ]
+reopen nodes:
+libvirt-3-format

tests/qemublocktestdata/checkpointdelete/snapshots-intermediate2-out.json

@@ -57,3 +57,6 @@
     }
   }
 ]
+reopen nodes:
+libvirt-3-format
+libvirt-2-format

tests/qemublocktestdata/checkpointdelete/snapshots-intermediate3-out.json

@@ -57,3 +57,5 @@
     }
   }
 ]
+reopen nodes:
+libvirt-2-format

tests/qemublocktestdata/checkpointdelete/snapshots-noparent-out.json

@@ -21,3 +21,7 @@
     }
   }
 ]
+reopen nodes:
+libvirt-5-format
+libvirt-4-format
+libvirt-3-format

tests/qemublocktestdata/checkpointdelete/snapshots-synthetic-checkpoint-intermediate1-out.json

@@ -27,3 +27,5 @@
     }
   }
 ]
+reopen nodes:
+libvirt-3-format

tests/qemublocktestdata/checkpointdelete/snapshots-synthetic-checkpoint-intermediate2-out.json

@@ -30,3 +30,5 @@
     }
   }
 ]
+reopen nodes:
+libvirt-2-format

tests/qemublocktestdata/checkpointdelete/snapshots-synthetic-checkpoint-intermediate3-out.json

@@ -57,3 +57,5 @@
     }
   }
 ]
+reopen nodes:
+libvirt-2-format

tests/qemublocktestdata/checkpointdelete/snapshots-synthetic-checkpoint-noparent-out.json

@@ -21,3 +21,7 @@
     }
   }
 ]
+reopen nodes:
+libvirt-5-format
+libvirt-4-format
+libvirt-3-format