backup: qemu: Implement metadata tracking for checkpoint APIs

A lot of this work heavily copies from the existing snapshot APIs.
What's more, this patch is (intentionally) very similar to the
checkpoint code just added in the test driver, to the point that qemu
checkpoints are not fully usable in this patch, but it at least
bisects and builds cleanly.  The separation between patches is done
because the grunt work of saving and restoring XML and tracking
relations between checkpoints is common to the test driver, while the
later patch adding integration with QMP is specific to qemu.

Also note that the interlocking to prevent checkpoints and snapshots
from existing at the same time will be a separate patch, to make it
easier to revert that restriction when we finally round out the design
for supporting interaction between the two concepts.
Signed-off-by: NEric Blake <eblake@redhat.com>

src/qemu/qemu_domain.c

@@ -56,6 +56,7 @@
 #include "logging/log_manager.h"
 #include "locking/domain_lock.h"
 #include "virdomainsnapshotobjlist.h"
+#include "virdomaincheckpointobjlist.h"
 
 #ifdef MAJOR_IN_MKDEV
 # include <sys/mkdev.h>
@@ -9138,6 +9139,37 @@ qemuDomainSnapshotWriteMetadata(virDomainObjPtr vm,
     return ret;
 }
 
+int
+qemuDomainCheckpointWriteMetadata(virDomainObjPtr vm,
+                                  virDomainMomentObjPtr checkpoint,
+                                  virCapsPtr caps,
+                                  virDomainXMLOptionPtr xmlopt,
+                                  const char *checkpointDir)
+{
+    unsigned int flags = VIR_DOMAIN_CHECKPOINT_FORMAT_SECURE;
+    virDomainCheckpointDefPtr def = virDomainCheckpointObjGetDef(checkpoint);
+    VIR_AUTOFREE(char *) newxml = NULL;
+    VIR_AUTOFREE(char *) chkDir = NULL;
+    VIR_AUTOFREE(char *) chkFile = NULL;
+
+    newxml = virDomainCheckpointDefFormat(def, caps, xmlopt, flags);
+    if (newxml == NULL)
+        return -1;
+
+    if (virAsprintf(&chkDir, "%s/%s", checkpointDir, vm->def->name) < 0)
+        return -1;
+    if (virFileMakePath(chkDir) < 0) {
+        virReportSystemError(errno, _("cannot create checkpoint directory '%s'"),
+                             chkDir);
+        return -1;
+    }
+
+    if (virAsprintf(&chkFile, "%s/%s.xml", chkDir, def->parent.name) < 0)
+        return -1;
+
+    return virXMLSaveFile(chkFile, NULL, "checkpoint-edit", newxml);
+}
+
 /* The domain is expected to be locked and inactive. Return -1 on normal
  * failure, 1 if we skipped a disk due to try_all.  */
 static int
@@ -9334,12 +9366,81 @@ qemuDomainSnapshotDiscardAllMetadata(virQEMUDriverPtr driver,
 }
 
 
+/* Discard one checkpoint (or its metadata), without reparenting any children.  */
+int
+qemuDomainCheckpointDiscard(virQEMUDriverPtr driver,
+                            virDomainObjPtr vm,
+                            virDomainMomentObjPtr chk,
+                            bool update_parent,
+                            bool metadata_only)
+{
+    virDomainMomentObjPtr parent = NULL;
+    VIR_AUTOUNREF(virQEMUDriverConfigPtr) cfg = virQEMUDriverGetConfig(driver);
+    VIR_AUTOFREE(char *) chkFile = NULL;
+
+    if (!metadata_only && !virDomainObjIsActive(vm)) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                       _("cannot remove checkpoint from inactive domain"));
+        return -1;
+    }
+
+    if (virAsprintf(&chkFile, "%s/%s/%s.xml", cfg->checkpointDir,
+                    vm->def->name, chk->def->name) < 0)
+        return -1;
+
+    /* TODO: Implement QMP sequence to merge bitmaps */
+    parent = virDomainCheckpointFindByName(vm->checkpoints,
+                                           chk->def->parent_name);
+
+    if (chk == virDomainCheckpointGetCurrent(vm->checkpoints)) {
+        virDomainCheckpointSetCurrent(vm->checkpoints, NULL);
+        if (update_parent && parent) {
+            virDomainCheckpointSetCurrent(vm->checkpoints, parent);
+            if (qemuDomainCheckpointWriteMetadata(vm, parent, driver->caps,
+                                                  driver->xmlopt,
+                                                  cfg->checkpointDir) < 0) {
+                VIR_WARN("failed to set parent checkpoint '%s' as current",
+                         chk->def->parent_name);
+                virDomainCheckpointSetCurrent(vm->checkpoints, NULL);
+            }
+        }
+    }
+
+    if (unlink(chkFile) < 0)
+        VIR_WARN("Failed to unlink %s", chkFile);
+    if (update_parent)
+        virDomainMomentDropParent(chk);
+    virDomainCheckpointObjListRemove(vm->checkpoints, chk);
+
+    return 0;
+}
+
+int
+qemuDomainCheckpointDiscardAllMetadata(virQEMUDriverPtr driver,
+                                       virDomainObjPtr vm)
+{
+    virQEMUMomentRemove rem = {
+        .driver = driver,
+        .vm = vm,
+        .metadata_only = true,
+        .momentDiscard = qemuDomainCheckpointDiscard,
+    };
+
+    virDomainCheckpointForEach(vm->checkpoints, qemuDomainMomentDiscardAll,
+                               &rem);
+    virDomainCheckpointObjListRemoveAll(vm->checkpoints);
+
+    return rem.err;
+}
+
+
 static void
 qemuDomainRemoveInactiveCommon(virQEMUDriverPtr driver,
                                virDomainObjPtr vm)
 {
     virQEMUDriverConfigPtr cfg;
     VIR_AUTOFREE(char *) snapDir = NULL;
+    VIR_AUTOFREE(char *) chkDir = NULL;
 
     cfg = virQEMUDriverGetConfig(driver);
 
@@ -9354,6 +9455,17 @@ qemuDomainRemoveInactiveCommon(virQEMUDriverPtr driver,
     } else if (rmdir(snapDir) < 0 && errno != ENOENT) {
         VIR_WARN("unable to remove snapshot directory %s", snapDir);
     }
+    /* Remove any checkpoint metadata prior to removing the domain */
+    if (qemuDomainCheckpointDiscardAllMetadata(driver, vm) < 0) {
+        VIR_WARN("unable to remove all checkpoints for domain %s",
+                 vm->def->name);
+    } else if (virAsprintf(&chkDir, "%s/%s", cfg->checkpointDir,
+                           vm->def->name) < 0) {
+        VIR_WARN("unable to remove checkpoint directory %s/%s",
+                 cfg->checkpointDir, vm->def->name);
+    } else if (rmdir(chkDir) < 0 && errno != ENOENT) {
+        VIR_WARN("unable to remove checkpoint directory %s", chkDir);
+    }
     qemuExtDevicesCleanupHost(driver, vm->def);
 
     virObjectUnref(cfg);

src/qemu/qemu_domain.h

@@ -755,6 +755,21 @@ int qemuDomainMomentDiscardAll(void *payload,
 int qemuDomainSnapshotDiscardAllMetadata(virQEMUDriverPtr driver,
                                          virDomainObjPtr vm);
 
+int qemuDomainCheckpointWriteMetadata(virDomainObjPtr vm,
+                                      virDomainMomentObjPtr checkpoint,
+                                      virCapsPtr caps,
+                                      virDomainXMLOptionPtr xmlopt,
+                                      const char *checkpointDir);
+
+int qemuDomainCheckpointDiscard(virQEMUDriverPtr driver,
+                                virDomainObjPtr vm,
+                                virDomainMomentObjPtr chk,
+                                bool update_current,
+                                bool metadata_only);
+
+int qemuDomainCheckpointDiscardAllMetadata(virQEMUDriverPtr driver,
+                                           virDomainObjPtr vm);
+
 void qemuDomainRemoveInactive(virQEMUDriverPtr driver,
                               virDomainObjPtr vm);