[libvirt] [PATCH 1/5] snapshot: Implement reverting for external disk snapshots
Povilas Kanapickas
povilas at radix.lt
Sun Oct 21 16:38:48 UTC 2018
Signed-off-by: Povilas Kanapickas <povilas at radix.lt>
---
src/qemu/qemu_driver.c | 246 +++++++++++++++++++++++++++++++++++++----
1 file changed, 224 insertions(+), 22 deletions(-)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index a52e2495d5..279e5d93aa 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -15952,19 +15952,194 @@ qemuDomainSnapshotHasMetadata(virDomainSnapshotPtr snapshot,
return ret;
}
+static int
+qemuDomainSnapshotRevertExternalSingleDisk(virQEMUDriverPtr driver,
+ virDomainDiskDefPtr revert_disk,
+ virDomainDiskDefPtr backing_disk)
+{
+ virCommandPtr cmd = NULL;
+ const char *qemuImgPath;
+ virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
+ int ret = -1;
+
+ if (!(qemuImgPath = qemuFindQemuImgBinary(driver)))
+ goto cleanup;
+
+ if (unlink(revert_disk->src->path) < 0)
+ VIR_WARN("Failed to overwrite current image for snapshot '%s'",
+ revert_disk->src->path);
+
+ /* TODO: maybe figure out the format from the backing_disk? */
+ revert_disk->src->format = VIR_STORAGE_FILE_QCOW2;
+ /* FIXME: what about revert_disk->src->backingStore ? */
+
+ /* creates cmd line args: qemu-img create -f qcow2 -o */
+ if (!(cmd = virCommandNewArgList(qemuImgPath,
+ "create",
+ "-f",
+ virStorageFileFormatTypeToString(revert_disk->src->format),
+ "-o",
+ NULL)))
+ goto cleanup;
+
+ /* adds cmd line arg: backing_file=/path/to/backing/file,backing_fmt=format */
+ virCommandAddArgFormat(cmd, "backing_file=%s,backing_fmt=%s",
+ backing_disk->src->path,
+ virStorageFileFormatTypeToString(backing_disk->src->format));
+
+ /* adds cmd line args: /path/to/target/file */
+ virCommandAddArg(cmd, revert_disk->src->path);
+
+ if (virCommandRun(cmd, NULL) < 0)
+ goto cleanup;
+
+ virCommandFree(cmd);
+ cmd = NULL;
+ ret = 0;
+
+ cleanup:
+ virCommandFree(cmd);
+ virObjectUnref(cfg);
+
+ return ret;
+}
+
+static void
+qemuComputeSnapshotDiskToDomainDiskMapping(virDomainSnapshotDefPtr snap_def,
+ virDomainDefPtr dom_def,
+ int* out_mapping)
+{
+ size_t i, j;
+ int found_idx;
+ virDomainSnapshotDiskDefPtr snap_disk;
+
+ for (i = 0; i < snap_def->ndisks; ++i) {
+ snap_disk = &(snap_def->disks[i]);
+ if (snap_disk->snapshot != VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL)
+ continue;
+
+ found_idx = -1;
+ for (j = 0; j < dom_def->ndisks; ++j) {
+ if (STREQ(dom_def->disks[j]->dst, snap_disk->name)) {
+ found_idx = j;
+ break;
+ }
+ }
+ out_mapping[i] = found_idx;
+ }
+}
+
+/* This function reverts an external snapshot disk state. With external disks
+ we can't just revert to the disks listed in the domain stored within the
+ snapshot, because it's read-only and might be used by other VMs in different
+ backing chains. Since the contents of the current disks will be discarded
+ in favor of data in the snapshot, we reuse them by resetting them and
+ pointing the backing image link to the disks listed within the snapshot.
+
+ The domain is expected to be inactive.
+
+ new_def is the new domain definition that will be stored to vm sometime in
+ the future.
+ */
+static int
+qemuDomainSnapshotRevertInactiveExternal(virQEMUDriverPtr driver,
+ virDomainObjPtr vm,
+ virDomainSnapshotObjPtr snap,
+ virDomainDefPtr new_def)
+{
+ /* We have the following disks recorded in the snapshot and the current
+ domain definition:
+
+ - the current disk state before the revert (vm->def->disks). We'll
+ discard and reuse them.
+ - the lists of disks that were snapshotted (snap->def->disks). We'll
+ use this information to figure out which disks to actually revert.
+ - the original disk state stored in the snapshot
+ (snap->def->dom->disks). We'll point reverted disks to use these
+ disks as backing images.
+
+ FIXME: what to do with disks that weren't included in all snapshots
+ within the hierrachy?
+ */
+ size_t i;
+ int* snap_disk_to_vm_def_disk_idx_map = NULL;
+ int* snap_disk_to_new_def_disk_idx_map = NULL;
+ int ret = -1;
+ virDomainSnapshotDiskDefPtr snap_disk;
+ virDomainDiskDefPtr backing_disk;
+ virDomainDiskDefPtr revert_disk;
+ virDomainDiskDefPtr new_disk;
+
+ if (VIR_ALLOC_N(snap_disk_to_vm_def_disk_idx_map, snap->def->ndisks) < 0)
+ goto cleanup;
+ if (VIR_ALLOC_N(snap_disk_to_new_def_disk_idx_map, snap->def->ndisks) < 0)
+ goto cleanup;
+
+ /* Figure out the matching disks from the current VM state. */
+ qemuComputeSnapshotDiskToDomainDiskMapping(snap->def, vm->def,
+ snap_disk_to_vm_def_disk_idx_map);
+ qemuComputeSnapshotDiskToDomainDiskMapping(snap->def, new_def,
+ snap_disk_to_new_def_disk_idx_map);
+
+ for (i = 0; i < snap->def->ndisks; ++i) {
+ snap_disk = &(snap->def->disks[i]);
+ if (snap_disk->snapshot != VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL)
+ continue;
+ if (snap_disk_to_vm_def_disk_idx_map[i] < 0 ||
+ snap_disk_to_new_def_disk_idx_map[i] < 0) {
+ // FIXME: we could create additional disks, but for now it's not
+ // supported.
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("all disks in the snapshots must have "
+ "equivalents in the current VM state."));
+ goto cleanup;
+ }
+ }
+
+ /* Discard old disk contents and point them to the backing disks */
+ for (i = 0; i < snap->def->ndisks; ++i) {
+ snap_disk = &(snap->def->disks[i]);
+
+ // Note that at the moment we don't support mixing internal and
+ // external snapshot modes for different disks, but skip non-external
+ // disks just in case.
+ if (snap_disk->snapshot != VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL)
+ continue;
+
+ backing_disk = snap->def->dom->disks[snap_disk->idx];
+ revert_disk = vm->def->disks[snap_disk_to_vm_def_disk_idx_map[i]];
+ if (qemuDomainSnapshotRevertExternalSingleDisk(driver, revert_disk,
+ backing_disk) < 0) {
+ goto cleanup;
+ }
+
+ /* FIXME: figure out which data exactly needs copying.
+ */
+ new_disk = new_def->disks[snap_disk_to_new_def_disk_idx_map[i]];
+ new_disk->src->format = revert_disk->src->format;
+ if (VIR_STRDUP(new_disk->src->path, revert_disk->src->path) < 0) {
+ goto cleanup;
+ }
+ }
+ ret = 0;
+
+cleanup:
+ VIR_FREE(snap_disk_to_vm_def_disk_idx_map);
+ VIR_FREE(snap_disk_to_new_def_disk_idx_map);
+ return ret;
+}
/* The domain is expected to be locked and inactive. */
static int
-qemuDomainSnapshotRevertInactive(virQEMUDriverPtr driver,
- virDomainObjPtr vm,
- virDomainSnapshotObjPtr snap)
+qemuDomainSnapshotRevertInactiveInternal(virQEMUDriverPtr driver,
+ virDomainObjPtr vm,
+ virDomainSnapshotObjPtr snap)
{
/* Try all disks, but report failure if we skipped any. */
int ret = qemuDomainSnapshotForEachQcow2(driver, vm, snap, "-a", true);
return ret > 0 ? -1 : ret;
}
-
static int
qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
unsigned int flags)
@@ -15981,6 +16156,7 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
virDomainDefPtr config = NULL;
virQEMUDriverConfigPtr cfg = NULL;
virCapsPtr caps = NULL;
+ bool is_external = false;
bool was_stopped = false;
qemuDomainSaveCookiePtr cookie;
virCPUDefPtr origCPU = NULL;
@@ -16043,11 +16219,13 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
goto endjob;
}
- if (virDomainSnapshotIsExternal(snap)) {
+ if (snap->def->memory == VIR_DOMAIN_SNAPSHOT_LOCATION_EXTERNAL) {
virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
- _("revert to external snapshot not supported yet"));
+ _("revert to external snapshot with memory state is "
+ "not supported yet"));
goto endjob;
}
+ is_external = virDomainSnapshotIsExternal(snap);
if (!(flags & VIR_DOMAIN_SNAPSHOT_REVERT_FORCE)) {
if (!snap->def->dom) {
@@ -16090,6 +16268,11 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
driver->xmlopt, NULL, true);
if (!config)
goto endjob;
+ } else if (is_external) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("revert to a an external snapshot without the VM "
+ "definition recorded is not supported."));
+ goto endjob;
}
cookie = (qemuDomainSaveCookiePtr) snap->def->cookie;
@@ -16110,8 +16293,8 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
/* Transitions 5, 6, 8, 9 */
/* Check for ABI compatibility. We need to do this check against
* the migratable XML or it will always fail otherwise */
+ bool compatible = true;
if (config) {
- bool compatible;
/* Replace the CPU in config and put the original one in priv
* once we're done. When we have the updated CPU def in the
@@ -16152,22 +16335,27 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
goto endjob;
}
virResetError(err);
- qemuProcessStop(driver, vm,
- VIR_DOMAIN_SHUTOFF_FROM_SNAPSHOT,
- QEMU_ASYNC_JOB_START, 0);
- virDomainAuditStop(vm, "from-snapshot");
- detail = VIR_DOMAIN_EVENT_STOPPED_FROM_SNAPSHOT;
- event = virDomainEventLifecycleNewFromObj(vm,
- VIR_DOMAIN_EVENT_STOPPED,
- detail);
- virObjectEventStateQueue(driver->domainEventState, event);
- /* Start after stop won't be an async start job, so
- * reset to none */
- jobType = QEMU_ASYNC_JOB_NONE;
- goto load;
}
}
+ if (!compatible || is_external) {
+ // If the snapshot is external we completely stop QEMU, adjust
+ // the disk state and restart it.
+ qemuProcessStop(driver, vm,
+ VIR_DOMAIN_SHUTOFF_FROM_SNAPSHOT,
+ QEMU_ASYNC_JOB_START, 0);
+ virDomainAuditStop(vm, "from-snapshot");
+ detail = VIR_DOMAIN_EVENT_STOPPED_FROM_SNAPSHOT;
+ event = virDomainEventLifecycleNewFromObj(vm,
+ VIR_DOMAIN_EVENT_STOPPED,
+ detail);
+ virObjectEventStateQueue(driver->domainEventState, event);
+ /* Start after stop won't be an async start job, so
+ * reset to none */
+ jobType = QEMU_ASYNC_JOB_NONE;
+ goto load;
+ }
+
priv = vm->privateData;
if (virDomainObjGetState(vm, NULL) == VIR_DOMAIN_RUNNING) {
/* Transitions 5, 6 */
@@ -16208,7 +16396,13 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
} else {
/* Transitions 2, 3 */
load:
+
was_stopped = true;
+
+ if (is_external &&
+ qemuDomainSnapshotRevertInactiveExternal(driver, vm, snap, config) < 0)
+ goto cleanup;
+
if (config)
virDomainObjAssignDef(vm, config, false, NULL);
@@ -16221,7 +16415,8 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
rc = qemuProcessStart(snapshot->domain->conn, driver, vm,
cookie ? cookie->cpu : NULL,
- jobType, NULL, -1, NULL, snap,
+ jobType, NULL, -1, NULL,
+ is_external ? NULL : snap,
VIR_NETDEV_VPORT_PROFILE_OP_CREATE,
start_flags);
virDomainAuditStart(vm, "from-snapshot", rc >= 0);
@@ -16291,11 +16486,18 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
detail);
}
- if (qemuDomainSnapshotRevertInactive(driver, vm, snap) < 0) {
+ if (is_external) {
+ rc = qemuDomainSnapshotRevertInactiveExternal(driver, vm, snap, config);
+ } else {
+ rc = qemuDomainSnapshotRevertInactiveInternal(driver, vm, snap);
+ }
+
+ if (rc < 0) {
qemuDomainRemoveInactive(driver, vm);
qemuProcessEndJob(driver, vm);
goto cleanup;
}
+
if (config)
virDomainObjAssignDef(vm, config, false, NULL);
--
2.17.1
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