[libvirt] [PATCH v8 19/21] backup: Wire up qemu full pull backup commands over QMP
Peter Krempa
pkrempa at redhat.com
Fri Apr 26 15:38:42 UTC 2019
On Wed, Apr 17, 2019 at 09:09:19 -0500, Eric Blake wrote:
> Time to actually issue the QMP transactions that start and
> stop backup commands (for now, just pull mode, not push).
> Starting a job has to kick off several pre-req steps, then
> a transaction, and additionally spawn an NBD server for pull
> mode; ending a job as well as failing partway through
> beginning a job has to unwind the earlier steps. Implementing
> push mode, as well as incremental pull and checkpoint creation,
> is deferred to later patches.
>
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
> src/qemu/qemu_domain.c | 18 ++-
> src/qemu/qemu_driver.c | 310 ++++++++++++++++++++++++++++++++++++++--
> src/qemu/qemu_process.c | 9 ++
> 3 files changed, 323 insertions(+), 14 deletions(-)
>
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index f4be948bae..db00c473d0 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -2684,17 +2684,25 @@ qemuDomainObjPrivateXMLParseBlockjobs(virQEMUDriverPtr driver,
> {
> xmlNodePtr node;
> int tmp;
> + size_t i;
> VIR_AUTOFREE(char *) active = NULL;
>
> if ((active = virXPathString("string(./blockjobs/@active)", ctxt)) &&
> (tmp = virTristateBoolTypeFromString(active)) > 0)
> priv->reconnectBlockjobs = tmp;
>
> - if ((node = virXPathNode("./domainbackup", ctxt)) &&
> - !(priv->backup = virDomainBackupDefParseNode(ctxt->doc, node,
> - driver->xmlopt,
> - VIR_DOMAIN_BACKUP_PARSE_INTERNAL)))
> - return -1;
> + if ((node = virXPathNode("./domainbackup", ctxt))) {
> + if (!(priv->backup = virDomainBackupDefParseNode(ctxt->doc, node,
> + driver->xmlopt,
> + VIR_DOMAIN_BACKUP_PARSE_INTERNAL)))
> + return -1;
> + /* The backup job is only stored in XML if backupBegin
> + * succeeded at exporting the disk, so no need to store disk
> + * state when we can just force-reset it to a known-good
> + * value. */
So why isn't it stored in a known-good state in the first place?
> + for (i = 0; i < priv->backup->ndisks; i++)
> + priv->backup->disks[i].state = VIR_DOMAIN_BACKUP_DISK_STATE_EXPORT;
> + }
>
> return 0;
> }
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index cca0b550b8..044b26196e 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -17693,8 +17693,80 @@ qemuDomainCheckpointDelete(virDomainCheckpointPtr checkpoint,
> return ret;
> }
>
> -static int qemuDomainBackupBegin(virDomainPtr domain, const char *diskXml,
> - const char *checkpointXml, unsigned int flags)
> +static int
> +qemuDomainBackupPrepare(virQEMUDriverPtr driver, virDomainObjPtr vm,
> + virDomainBackupDefPtr def)
> +{
> + int ret = -1;
> + size_t i;
> +
> + if (qemuBlockNodeNamesDetect(driver, vm, QEMU_ASYNC_JOB_NONE) < 0)
> + goto cleanup;
See previous comments regarding this function call.
> + for (i = 0; i < def->ndisks; i++) {
> + virDomainBackupDiskDef *disk = &def->disks[i];
> + virStorageSourcePtr src = vm->def->disks[disk->idx]->src;
> +
> + if (!disk->store)
> + continue;
> + if (virAsprintf(&disk->store->nodeformat, "tmp-%s", disk->name) < 0)
Use a somewhat more descriptive temporary prefix. Also if blockdev-del fails
after a job you won't be ever able to start a new job until the VM is
restarted as the node name will always be the same.
> + goto cleanup;
> + if (!disk->store->format)
> + disk->store->format = VIR_STORAGE_FILE_QCOW2;
> + if (def->incremental) {
> + if (src->format != VIR_STORAGE_FILE_QCOW2) {
> + virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
> + _("incremental backup of %s requires qcow2"),
> + disk->name);
> + goto cleanup;
> + }
> + }
> + }
> + ret = 0;
> + cleanup:
> + return ret;
> +}
> +
> +/* Called while monitor lock is held. Best-effort cleanup. */
> +static int
> +qemuDomainBackupDiskCleanup(virQEMUDriverPtr driver, virDomainObjPtr vm,
> + virDomainBackupDiskDef *disk, bool incremental)
> +{
> + qemuDomainObjPrivatePtr priv = vm->privateData;
> + const char *node = vm->def->disks[disk->idx]->src->nodeformat;
> + int ret = 0;
> +
> + if (!disk->store)
> + return 0;
> + if (disk->state >= VIR_DOMAIN_BACKUP_DISK_STATE_EXPORT) {
> + /* No real need to use nbd-server-remove, since we will
> + * shortly be calling nbd-server-stop. */
> + }
> + if (incremental && disk->state >= VIR_DOMAIN_BACKUP_DISK_STATE_BITMAP &&
> + qemuMonitorDeleteBitmap(priv->mon, node, disk->store->nodeformat) < 0) {
> + VIR_WARN("Unable to remove temp bitmap for disk %s after backup",
> + disk->name);
> + ret = -1;
> + }
> + if (disk->state >= VIR_DOMAIN_BACKUP_DISK_STATE_READY &&
> + qemuMonitorBlockdevDel(priv->mon, disk->store->nodeformat) < 0) {
You also need to blockdev-del the storage layer here.
> + VIR_WARN("Unable to remove temp disk %s after backup",
> + disk->name);
> + ret = -1;
> + }
> + if (disk->state >= VIR_DOMAIN_BACKUP_DISK_STATE_LABEL)
> + qemuDomainDiskChainElementRevoke(driver, vm, disk->store);
> + if (disk->state >= VIR_DOMAIN_BACKUP_DISK_STATE_CREATED &&
> + disk->store->detected && unlink(disk->store->path) < 0) {
> + VIR_WARN("Unable to unlink temp disk %s after backup",
> + disk->store->path);
> + ret = -1;
> + }
> + return ret;
> +}
> +
> +static int
> +qemuDomainBackupBegin(virDomainPtr domain, const char *diskXml,
> + const char *checkpointXml, unsigned int flags)
> {
> virQEMUDriverPtr driver = domain->conn->privateData;
> virDomainObjPtr vm = NULL;
[...]
> @@ -17747,25 +17826,145 @@ static int qemuDomainBackupBegin(virDomainPtr domain, const char *diskXml,
> if (!(def = virDomainBackupDefParseString(diskXml, driver->xmlopt, 0)))
> goto cleanup;
>
> + if (def->type == VIR_DOMAIN_BACKUP_TYPE_PULL) {
> + if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_NBD_BITMAP)) {
> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> + _("qemu binary lacks pull-mode backup support"));
> + goto cleanup;
> + }
> + if (!def->server) {
> + if (VIR_ALLOC(def->server) < 0)
> + goto cleanup;
> + def->server->transport = VIR_STORAGE_NET_HOST_TRANS_TCP;
> + if (VIR_STRDUP(def->server->name, "localhost") < 0)
> + goto cleanup;
> + }
> + switch ((virStorageNetHostTransport)def->server->transport) {
> + case VIR_STORAGE_NET_HOST_TRANS_TCP:
> + /* TODO: Update qemu.conf to provide a port range,
> + * probably starting at 10809, for obtaining automatic
> + * port via virPortAllocatorAcquire, as well as store
> + * somewhere if we need to call virPortAllocatorRelease
> + * during BackupEnd. Until then, user must provide port */
> + if (!def->server->port) {
> + virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> + _("<domainbackup> must specify TCP port for now"));
> + goto cleanup;
> + }
> + break;
> + case VIR_STORAGE_NET_HOST_TRANS_UNIX:
> + /* TODO: Do we need to mess with selinux? */
> + break;
> + case VIR_STORAGE_NET_HOST_TRANS_RDMA:
> + case VIR_STORAGE_NET_HOST_TRANS_LAST:
> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> + _("unexpected transport in <domainbackup>"));
> + goto cleanup;
> + }
> + } else {
> + virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> + _("push mode backups not supported yet"));
> + goto cleanup;
> + }
> + if (def->incremental) {
> + if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_BITMAP_MERGE)) {
> + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> + _("qemu binary lacks persistent bitmaps support"));
> + goto cleanup;
> + }
> + virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> + _("cannot create incremental backups yet"));
> + goto cleanup;
> + }
> +
> + if (!(qemuImgPath = qemuFindQemuImgBinary(driver)))
> + goto cleanup;
> +
> /* We are going to modify the domain below. */
> if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
> goto cleanup;
>
> - priv = vm->privateData;
> if (priv->backup) {
> virReportError(VIR_ERR_OPERATION_INVALID,
> "%s", _("another backup job is already running"));
> goto endjob;
> }
>
> - if (virDomainBackupAlignDisks(def, vm->def, suffix) < 0)
> + if (virDomainBackupAlignDisks(def, vm->def, suffix) < 0 ||
> + qemuDomainBackupPrepare(driver, vm, def) < 0)
> goto endjob;
>
> /* actually start the checkpoint. 2x2 array of push/pull, full/incr,
> plus additional tweak if checkpoint requested */
> - /* TODO: issue QMP commands:
> - - pull: nbd-server-start with <server> from user (or autogenerate server)
> - - push/pull: blockdev-add per <disk>
> + qemuDomainObjEnterMonitor(driver, vm);
> + /* - push/pull: blockdev-add per <disk> */
> + for (i = 0; i < def->ndisks; i++) {
> + virDomainBackupDiskDef *disk = &def->disks[i];
> + virJSONValuePtr file;
> + virStorageSourcePtr src = vm->def->disks[disk->idx]->src;
> + const char *node = src->nodeformat;
> +
> + if (!disk->store)
> + continue;
> + if (qemuDomainStorageFileInit(driver, vm, disk->store, src) < 0)
virStorageFileDeinit is never called in this function.
> + goto endmon;
> + if (disk->store->detected) {
> + if (virStorageFileCreate(disk->store) < 0) {
> + virReportSystemError(errno,
> + _("failed to create image file '%s'"),
> + NULLSTR(disk->store->path));
> + goto endmon;
> + }
> + disk->state = VIR_DOMAIN_BACKUP_DISK_STATE_CREATED;
> + }
> + if (qemuDomainDiskChainElementPrepare(driver, vm, disk->store, false,
> + true) < 0)
> + goto endmon;
> + disk->state = VIR_DOMAIN_BACKUP_DISK_STATE_LABEL;
> + if (disk->store->detected) {
> + virBuffer buf = VIR_BUFFER_INITIALIZER;
> +
> + /* Force initialization of scratch/target file to new qcow2 */
> + if (!(cmd = virCommandNewArgList(qemuImgPath,
> + "create",
> + "-f",
> + virStorageFileFormatTypeToString(disk->store->format),
> + "-o",
> + NULL)))
> + goto endmon;
> + virBufferAsprintf(&buf, "backing_fmt=%s,backing_file=",
> + virStorageFileFormatTypeToString(src->format));
> + virQEMUBuildBufferEscapeComma(&buf, src->path);
> + virCommandAddArgBuffer(cmd, &buf);
> +
> + virQEMUBuildBufferEscapeComma(&buf, disk->store->path);
> + virCommandAddArgBuffer(cmd, &buf);
> + if (virCommandRun(cmd, NULL) < 0)
> + goto endmon;
> + virCommandFree(cmd);
> + cmd = NULL;
> + }
> +
> + if (virJSONValueObjectCreate(&file,
> + "s:driver", "file",
> + "s:filename", disk->store->path,
> + NULL) < 0)
> + goto endmon;
> + if (virJSONValueObjectCreate(&json,
> + "s:driver", virStorageFileFormatTypeToString(disk->store->format),
We have helpers to create these froma virStorageSource. How about reusing those?
> + "s:node-name", disk->store->nodeformat,
> + "a:file", &file,
The rest of the blockdev integration code which is already present
always plugs in the storage and format layer separately. This should do
the same.
> + "s:backing", node, NULL) < 0) {
> + virJSONValueFree(file);
> + goto endmon;
> + }
> + if (qemuMonitorBlockdevAdd(priv->mon, json) < 0)
> + goto endmon;
> + json = NULL;
> + disk->state = VIR_DOMAIN_BACKUP_DISK_STATE_READY;
> + }
> +
> + /* TODO:
> - incr: bitmap-add of tmp, bitmap-merge per <disk>
> - transaction, containing:
> - push+full: blockdev-backup sync:full
> @@ -17773,8 +17972,76 @@ static int qemuDomainBackupBegin(virDomainPtr domain, const char *diskXml,
> - pull+full: blockdev-backup sync:none
> - pull+incr: blockdev-backup sync:none, bitmap-disable of tmp
> - if checkpoint: bitmap-disable of old, bitmap-add of new
> + */
> + if (!(json = virJSONValueNewArray()))
> + goto endmon;
> + for (i = 0; i < def->ndisks; i++) {
> + virDomainBackupDiskDef *disk = &def->disks[i];
> + virStorageSourcePtr src = vm->def->disks[disk->idx]->src;
> +
> + if (!disk->store)
> + continue;
> + if (qemuMonitorJSONTransactionAdd(json,
> + "blockdev-backup",
> + "s:device", src->nodeformat,
> + "s:target", disk->store->nodeformat,
> + "s:sync", "none",
> + "s:job-id", disk->name,
This should probably be somewhat more descriptive to prevent collisions
if we ever want to allow multiple jobs
> + NULL) < 0)
> + goto endmon;
> + }
> + if (qemuMonitorTransaction(priv->mon, &json) < 0)
> + goto endmon;
> + job_started = true;
> +
> + /*
> + - pull: nbd-server-start with <server> from user (or autogenerate server)
> - pull: nbd-server-add per <disk>, including bitmap for incr
> */
> + if (def->type == VIR_DOMAIN_BACKUP_TYPE_PULL) {
> + if (qemuMonitorNBDServerStart(priv->mon, def->server, NULL) < 0)
> + goto endmon;
> + nbd_running = true;
> + for (i = 0; i < def->ndisks; i++) {
> + virDomainBackupDiskDef *disk = &def->disks[i];
> +
> + if (!disk->store)
> + continue;
> + if (qemuMonitorNBDServerAdd(priv->mon, disk->store->nodeformat,
> + disk->name, false,
> + def->incremental ? disk->name :
> + NULL) < 0)
> + goto endmon;
> + disk->state = VIR_DOMAIN_BACKUP_DISK_STATE_EXPORT;
> + }
> + }
> +
> + ret = 0;
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