qemu: backup: Rewrite backup bitmap handling to the new bitmap semantics

Reuse qemuBlockGetBitmapMergeActions which allows removal of the ad-hoc
implementation of bitmap merging for backup. The new approach is simpler
and also more robust in case some of the bitmaps break as they remove
the dependency on the whole chain of bitmaps working.

The new approach also allows backups if a snapshot is created outside of
libvirt.

Additionally the code is greatly simplified.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

src/qemu/qemu_backup.c

@@ -173,199 +173,58 @@ qemuBackupDiskDataCleanup(virDomainObjPtr vm,
 }
 
 
-/**
+int
- * qemuBackupBeginCollectIncrementalCheckpoints:
+qemuBackupDiskPrepareOneBitmapsChain(virStorageSourcePtr backingChain,
- * @vm: domain object
+                                     virStorageSourcePtr targetsrc,
- * @incrFrom: name of checkpoint representing starting point of incremental backup
+                                     const char *targetbitmap,
- *
+                                     const char *incremental,
- * Returns a NULL terminated list of pointers to checkpoint definitions in
+                                     virJSONValuePtr actions,
- * chronological order starting from the 'current' checkpoint until reaching
+                                     virHashTablePtr blockNamedNodeData)
- * @incrFrom.
- */
-static virDomainMomentDefPtr *
-qemuBackupBeginCollectIncrementalCheckpoints(virDomainObjPtr vm,
-                                             const char *incrFrom)
 {
-    virDomainMomentObjPtr n = virDomainCheckpointGetCurrent(vm->checkpoints);
+    g_autoptr(virJSONValue) tmpactions = NULL;
-    g_autofree virDomainMomentDefPtr *incr = NULL;
-    size_t nincr = 0;
 
-    while (n) {
+    if (qemuBlockGetBitmapMergeActions(backingChain, NULL, targetsrc,
-        virDomainMomentDefPtr def = n->def;
+                                       incremental, targetbitmap, NULL,
-
+                                       &tmpactions,
-        if (VIR_APPEND_ELEMENT_COPY(incr, nincr, def) < 0)
+                                       blockNamedNodeData) < 0)
-            return NULL;
-
-        if (STREQ(def->name, incrFrom)) {
-            def = NULL;
-            if (VIR_APPEND_ELEMENT_COPY(incr, nincr, def) < 0)
-                return NULL;
-
-            return g_steal_pointer(&incr);
-        }
-
-        if (!n->def->parent_name)
-            break;
-
-        n = virDomainCheckpointFindByName(vm->checkpoints, n->def->parent_name);
-    }
-
-    virReportError(VIR_ERR_OPERATION_INVALID,
-                   _("could not locate checkpoint '%s' for incremental backup"),
-                   incrFrom);
-    return NULL;
-}
-
-
-static int
-qemuBackupGetBitmapMergeRange(virStorageSourcePtr from,
-                              const char *bitmapname,
-                              virJSONValuePtr *actions,
-                              virStorageSourcePtr *to,
-                              const char *diskdst,
-                              virHashTablePtr blockNamedNodeData)
-{
-    g_autoptr(virJSONValue) act = virJSONValueNewArray();
-    virStorageSourcePtr tmpsrc = NULL;
-    virStorageSourcePtr n;
-    bool foundbitmap = false;
-
-    for (n = from; virStorageSourceIsBacking(n); n = n->backingStore) {
-        qemuBlockNamedNodeDataBitmapPtr bitmap = NULL;
-
-        if (!(bitmap = qemuBlockNamedNodeDataGetBitmapByName(blockNamedNodeData,
-                                                             n,
-                                                             bitmapname)))
-            break;
-
-        foundbitmap = true;
-
-        if (bitmap->inconsistent) {
-            virReportError(VIR_ERR_INVALID_ARG,
-                           _("bitmap '%s' for image '%s%u' is inconsistent"),
-                           bitmap->name, diskdst, n->id);
-            return -1;
-        }
-
-        if (qemuMonitorTransactionBitmapMergeSourceAddBitmap(act,
-                                                             n->nodeformat,
-                                                             bitmapname) < 0)
-            return -1;
-
-        tmpsrc = n;
-    }
-
-    if (!foundbitmap) {
-        virReportError(VIR_ERR_INVALID_ARG,
-                       _("failed to find bitmap '%s' in image '%s%u'"),
-                       bitmapname, diskdst, from->id);
         return -1;
-    }
 
-    *actions = g_steal_pointer(&act);
+    if (tmpactions &&
-    *to = tmpsrc;
+        virJSONValueArrayConcat(actions, tmpactions) < 0)
+        return -1;
 
     return 0;
 }
 
 
-virJSONValuePtr
-qemuBackupDiskPrepareOneBitmapsChain(virDomainMomentDefPtr *incremental,
-                                     virStorageSourcePtr backingChain,
-                                     virHashTablePtr blockNamedNodeData,
-                                     const char *diskdst)
-{
-    g_autoptr(virJSONValue) ret = NULL;
-    size_t incridx = 0;
-    virStorageSourcePtr n = backingChain;
-
-    ret = virJSONValueNewArray();
-
-    for (incridx = 0; incremental[incridx]; incridx++) {
-        g_autoptr(virJSONValue) tmp = virJSONValueNewArray();
-        virStorageSourcePtr tmpsrc = NULL;
-        virDomainCheckpointDefPtr chkdef = (virDomainCheckpointDefPtr) incremental[incridx];
-        bool checkpoint_has_disk = false;
-        size_t i;
-
-        for (i = 0; i < chkdef->ndisks; i++) {
-            if (STRNEQ_NULLABLE(diskdst, chkdef->disks[i].name))
-                continue;
-
-            if (chkdef->disks[i].type == VIR_DOMAIN_CHECKPOINT_TYPE_BITMAP)
-                checkpoint_has_disk = true;
-
-            break;
-        }
-
-        if (!checkpoint_has_disk) {
-            if (!incremental[incridx + 1]) {
-                virReportError(VIR_ERR_INVALID_ARG,
-                               _("disk '%s' not found in checkpoint '%s'"),
-                               diskdst, incremental[incridx]->name);
-                return NULL;
-            }
-
-            continue;
-        }
-
-        if (qemuBackupGetBitmapMergeRange(n, incremental[incridx]->name,
-                                          &tmp, &tmpsrc, diskdst,
-                                          blockNamedNodeData) < 0)
-            return NULL;
-
-        if (virJSONValueArrayConcat(ret, tmp) < 0)
-            return NULL;
-
-        n = tmpsrc;
-    }
-
-    return g_steal_pointer(&ret);
-}
-
-
 static int
 qemuBackupDiskPrepareOneBitmaps(struct qemuBackupDiskData *dd,
                                 virJSONValuePtr actions,
-                                virDomainMomentDefPtr *incremental,
                                 virHashTablePtr blockNamedNodeData)
 {
-    g_autoptr(virJSONValue) mergebitmaps = NULL;
+    if (!qemuBlockBitmapChainIsValid(dd->domdisk->src,
-    g_autoptr(virJSONValue) mergebitmapsstore = NULL;
+                                     dd->backupdisk->incremental,
+                                     blockNamedNodeData)) {
+        virReportError(VIR_ERR_INVALID_ARG,
+                       _("missing or broken bitmap '%s' for disk '%s'"),
+                       dd->backupdisk->incremental, dd->domdisk->dst);
+        return -1;
+    }
 
-    if (!(mergebitmaps = qemuBackupDiskPrepareOneBitmapsChain(incremental,
+    if (qemuBackupDiskPrepareOneBitmapsChain(dd->domdisk->src,
-                                                              dd->domdisk->src,
+                                             dd->domdisk->src,
-                                                              blockNamedNodeData,
+                                             dd->incrementalBitmap,
-                                                              dd->domdisk->dst)))
+                                             dd->backupdisk->incremental,
+                                             actions,
+                                             blockNamedNodeData) < 0)
         return -1;
 
-    if (!(mergebitmapsstore = virJSONValueCopy(mergebitmaps)))
+    if (qemuBackupDiskPrepareOneBitmapsChain(dd->domdisk->src,
-        return -1;
+                                             dd->store,
-
+                                             dd->incrementalBitmap,
-    if (qemuMonitorTransactionBitmapAdd(actions,
+                                             dd->backupdisk->incremental,
-                                        dd->domdisk->src->nodeformat,
+                                             actions,
-                                        dd->incrementalBitmap,
+                                             blockNamedNodeData) < 0)
-                                        false,
-                                        true, 0) < 0)
-        return -1;
-
-    if (qemuMonitorTransactionBitmapMerge(actions,
-                                          dd->domdisk->src->nodeformat,
-                                          dd->incrementalBitmap,
-                                          &mergebitmaps) < 0)
-        return -1;
-
-    if (qemuMonitorTransactionBitmapAdd(actions,
-                                        dd->store->nodeformat,
-                                        dd->incrementalBitmap,
-                                        false,
-                                        true, 0) < 0)
-        return -1;
-
-    if (qemuMonitorTransactionBitmapMerge(actions,
-                                          dd->store->nodeformat,
-                                          dd->incrementalBitmap,
-                                          &mergebitmapsstore) < 0)
         return -1;
 
     return 0;
@@ -382,7 +241,6 @@ qemuBackupDiskPrepareDataOne(virDomainObjPtr vm,
                              virQEMUDriverConfigPtr cfg)
 {
     qemuDomainObjPrivatePtr priv = vm->privateData;
-    g_autofree virDomainMomentDefPtr *incremental = NULL;
 
     /* set data structure */
     dd->backupdisk = backupdisk;
@@ -421,16 +279,12 @@ qemuBackupDiskPrepareDataOne(virDomainObjPtr vm,
         return -1;
 
     if (dd->backupdisk->incremental) {
-        if (!(incremental = qemuBackupBeginCollectIncrementalCheckpoints(vm, dd->backupdisk->incremental)))
-            return -1;
-
         if (dd->backupdisk->exportbitmap)
             dd->incrementalBitmap = g_strdup(dd->backupdisk->exportbitmap);
         else
             dd->incrementalBitmap = g_strdup_printf("backup-%s", dd->domdisk->dst);
 
-        if (qemuBackupDiskPrepareOneBitmaps(dd, actions, incremental,
+        if (qemuBackupDiskPrepareOneBitmaps(dd, actions, blockNamedNodeData) < 0)
-                                            blockNamedNodeData) < 0)
             return -1;
     }
 
@@ -884,8 +738,8 @@ qemuBackupBegin(virDomainObjPtr vm,
     if (!(blockNamedNodeData = qemuBlockGetNamedNodeData(vm, QEMU_ASYNC_JOB_BACKUP)))
         goto endjob;
 
-    if ((ndd = qemuBackupDiskPrepareData(vm, def, blockNamedNodeData,
+    if ((ndd = qemuBackupDiskPrepareData(vm, def, blockNamedNodeData, actions,
-                                         actions, cfg, &dd)) <= 0) {
+                                         cfg, &dd)) <= 0) {
         if (ndd == 0) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("no disks selected for backup"));

src/qemu/qemu_backup.h

@@ -53,8 +53,10 @@ qemuBackupGetJobInfoStats(virQEMUDriverPtr driver,
                           qemuDomainJobInfoPtr jobInfo);
 
 /* exported for testing */
-virJSONValuePtr
+int
-qemuBackupDiskPrepareOneBitmapsChain(virDomainMomentDefPtr *incremental,
+qemuBackupDiskPrepareOneBitmapsChain(virStorageSourcePtr backingChain,
-                                     virStorageSourcePtr backingChain,
+                                     virStorageSourcePtr targetsrc,
-                                     virHashTablePtr blockNamedNodeData,
+                                     const char *targetbitmap,
-                                     const char *diskdst);
+                                     const char *incremental,
+                                     virJSONValuePtr actions,
+                                     virHashTablePtr blockNamedNodeData);

tests/qemublocktest.c

@@ -716,65 +716,6 @@ testQemuBitmapGetFakeChainEntry(virStorageSourcePtr src,
 }
 
 
-typedef virDomainMomentDefPtr testMomentList;
-
-static void
-testMomentListFree(testMomentList *list)
-{
-    testMomentList *tmp = list;
-
-    if (!list)
-        return;
-
-    while (*tmp) {
-        virObjectUnref(*tmp);
-        tmp++;
-    }
-
-    g_free(list);
-}
-
-G_DEFINE_AUTOPTR_CLEANUP_FUNC(testMomentList, testMomentListFree);
-
-static virDomainMomentDefPtr
-testQemuBackupGetIncrementalMoment(const char *name)
-{
-    virDomainCheckpointDefPtr checkpoint = NULL;
-
-    if (!(checkpoint = virDomainCheckpointDefNew()))
-        abort();
-
-    checkpoint->disks = g_new0(virDomainCheckpointDiskDef, 1);
-    checkpoint->ndisks = 1;
-
-    checkpoint->disks[0].name = g_strdup("testdisk");
-    checkpoint->disks[0].type = VIR_DOMAIN_CHECKPOINT_TYPE_BITMAP;
-
-    checkpoint->parent.name = g_strdup(name);
-
-    return (virDomainMomentDefPtr) checkpoint;
-}
-
-
-static virDomainMomentDefPtr *
-testQemuBackupGetIncremental(const char *incFrom)
-{
-    const char *checkpoints[] = {"current", "d", "c", "b", "a"};
-    virDomainMomentDefPtr *incr;
-    size_t i;
-
-    incr = g_new0(virDomainMomentDefPtr, G_N_ELEMENTS(checkpoints) + 1);
-
-    for (i = 0; i < G_N_ELEMENTS(checkpoints); i++) {
-        incr[i] = testQemuBackupGetIncrementalMoment(checkpoints[i]);
-
-        if (STREQ(incFrom, checkpoints[i]))
-            break;
-    }
-
-    return incr;
-}
-
 static const char *backupDataPrefix = "qemublocktestdata/backupmerge/";
 
 struct testQemuBackupIncrementalBitmapCalculateData {
@@ -791,10 +732,10 @@ testQemuBackupIncrementalBitmapCalculate(const void *opaque)
     const struct testQemuBackupIncrementalBitmapCalculateData *data = opaque;
     g_autoptr(virJSONValue) nodedatajson = NULL;
     g_autoptr(virHashTable) nodedata = NULL;
-    g_autoptr(virJSONValue) mergebitmaps = NULL;
+    g_autoptr(virJSONValue) actions = virJSONValueNewArray();
-    g_autofree char *actual = NULL;
     g_autofree char *expectpath = NULL;
-    g_autoptr(testMomentList) incremental = NULL;
+    g_autoptr(virStorageSource) target = NULL;
+    g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
 
     expectpath = g_strdup_printf("%s/%s%s-out.json", abs_srcdir,
                                  backupDataPrefix, data->name);
@@ -808,19 +749,24 @@ testQemuBackupIncrementalBitmapCalculate(const void *opaque)
         return -1;
     }
 
-    incremental = testQemuBackupGetIncremental(data->incremental);
+    if (!(target = virStorageSourceNew()))
+        return -1;
 
-    if ((mergebitmaps = qemuBackupDiskPrepareOneBitmapsChain(incremental,
+    target->nodeformat = g_strdup_printf("target_node");
-                                                             data->chain,
+
-                                                             nodedata,
+    if (qemuBackupDiskPrepareOneBitmapsChain(data->chain,
-                                                             "testdisk"))) {
+                                             target,
-        if (!(actual = virJSONValueToString(mergebitmaps, true)))
+                                             "target-bitmap-name",
+                                             data->incremental,
+                                             actions,
+                                             nodedata) >= 0) {
+        if (virJSONValueToBuffer(actions, &buf, true) < 0)
             return -1;
     } else {
-        actual = g_strdup("NULL\n");
+        virBufferAddLit(&buf, "NULL\n");
     }
 
-    return virTestCompareToFile(actual, expectpath);
+    return virTestCompareToFile(virBufferCurrentContent(&buf), expectpath);
 }
 
 

tests/qemublocktestdata/backupmerge/empty-out.json

@@ -1 +1,3 @@
-NULL
+[
+
+]