Re: [libvirt] [PATCHv4 08/18] blockjob: react to active block copy

For now, disk migration via block copy job is not implemented. But when we do implement it, we have to deal with the fact that qemu does not provide an easy way to re-start a qemu process with mirroring still intact (it _might_ be possible by using qemu -S then an initial 'drive-mirror' with disk reuse before starting the domain, but that gets hairy). Even something like 'virDomainSave' becomes hairy, if you realize the implications that 'virDomainRestore' would be stuck with recreating the same mirror layout. But if we step back and look at the bigger picture, we realize that the initial client of live storage migration via disk mirroring is oVirt, which always uses transient domains, and that if a transient domain is destroyed while a mirror exists, oVirt can easily restart the storage migration by creating a new domain that visits just the source storage, with no loss in data. We can make life a lot easier by being cowards, and forbidding certain operations on a domain. This patch guarantees that we never get in a state where we would have to restart a domain with a mirroring block copy, by preventing saves, snapshots, hot unplug of a disk in use, and conversion to a persistent domain. * src/conf/domain_conf.h (virDomainHasDiskMirror): New prototype. * src/conf/domain_conf.c (virDomainHasDiskMirror): New function. * src/libvirt_private.syms (domain_conf.h): Export it. * src/qemu/qemu_driver.c (qemuDomainSaveInternal) (qemuDomainSnapshotCreateXML, qemuDomainRevertToSnapshot) (qemuDomainBlockJobImpl, qemudDomainDefine): Prevent dangerous actions while block copy is already in action. * src/qemu/qemu_hotplug.c (qemuDomainDetachDiskDevice): Likewise. --- src/conf/domain_conf.c | 12 ++++++++++++ src/conf/domain_conf.h | 1 + src/libvirt_private.syms | 1 + src/qemu/qemu_driver.c | 31 ++++++++++++++++++++++++++++++- src/qemu/qemu_hotplug.c | 7 +++++++ 5 files changed, 51 insertions(+), 1 deletions(-) diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 8899653..3aa6861 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -7183,6 +7183,18 @@ virDomainDiskRemoveByName(virDomainDefPtr def, const char *name) return virDomainDiskRemove(def, i); } +/* Return true if VM has at least one disk involved in a current block + * copy job (that is, with a <mirror> element in the disk xml). */ +bool +virDomainHasDiskMirror(virDomainObjPtr vm) +{ + int i; + for (i = 0; i < vm->def->ndisks; i++) + if (vm->def->disks[i]->mirror) + return true; + return false; +} + int virDomainNetInsert(virDomainDefPtr def, virDomainNetDefPtr net) { if (VIR_REALLOC_N(def->nets, def->nnets + 1) < 0) diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index abc953d..77c501c 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -1954,6 +1954,7 @@ virDomainDiskDefPtr virDomainDiskRemove(virDomainDefPtr def, size_t i); virDomainDiskDefPtr virDomainDiskRemoveByName(virDomainDefPtr def, const char *name); +bool virDomainHasDiskMirror(virDomainObjPtr vm); int virDomainNetIndexByMac(virDomainDefPtr def, const unsigned char *mac); int virDomainNetInsert(virDomainDefPtr def, virDomainNetDefPtr net); diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index a90f8a0..570940d 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -354,6 +354,7 @@ virDomainGraphicsSpiceZlibCompressionTypeFromString; virDomainGraphicsSpiceZlibCompressionTypeToString; virDomainGraphicsTypeFromString; virDomainGraphicsTypeToString; +virDomainHasDiskMirror; virDomainHostdevDefAlloc; virDomainHostdevDefClear; virDomainHostdevDefFree; diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 425d340..b0937eb 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -2558,6 +2558,11 @@ qemuDomainSaveInternal(struct qemud_driver *driver, virDomainPtr dom, "%s", _("domain is marked for auto destroy")); goto cleanup; } + if (virDomainHasDiskMirror(vm)) { + qemuReportError(VIR_ERR_BLOCK_COPY_ACTIVE, "%s", + _("domain has active block copy job")); + goto cleanup; + } memset(&header, 0, sizeof(header)); memcpy(header.magic, QEMUD_SAVE_PARTIAL, sizeof(header.magic)); @@ -4947,6 +4952,12 @@ static virDomainPtr qemudDomainDefine(virConnectPtr conn, const char *xml) { goto cleanup; } def = NULL; + if (virDomainHasDiskMirror(vm)) { + qemuReportError(VIR_ERR_BLOCK_COPY_ACTIVE, "%s", + _("domain has active block copy job")); + virDomainObjAssignDef(vm, NULL, false); + goto cleanup; + } vm->persistent = 1;

if (virDomainSaveConfig(driver->configDir, @@ -10262,6 +10273,12 @@ qemuDomainSnapshotCreateXML(virDomainPtr domain, "%s", _("domain is marked for auto destroy")); goto cleanup; } + if (virDomainHasDiskMirror(vm)) { + qemuReportError(VIR_ERR_BLOCK_COPY_ACTIVE, "%s", + _("domain has active block copy job")); + goto cleanup; + } + if (!vm->persistent && (flags & VIR_DOMAIN_SNAPSHOT_CREATE_HALT)) { qemuReportError(VIR_ERR_OPERATION_INVALID, "%s", _("cannot halt after transient domain snapshot")); @@ -10869,6 +10886,11 @@ static int qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot, _("no domain with matching uuid '%s'"), uuidstr); goto cleanup; } + if (virDomainHasDiskMirror(vm)) { + qemuReportError(VIR_ERR_BLOCK_COPY_ACTIVE, "%s", + _("domain has active block copy job")); + goto cleanup; + } snap = virDomainSnapshotFindByName(&vm->snapshots, snapshot->name); if (!snap) { @@ -11607,6 +11629,7 @@ qemuDomainBlockJobImpl(virDomainPtr dom, const char *path, const char *base, char uuidstr[VIR_UUID_STRING_BUFLEN]; char *device = NULL; int ret = -1; + int idx; qemuDriverLock(driver); virUUIDFormat(dom->uuid, uuidstr); @@ -11617,7 +11640,7 @@ qemuDomainBlockJobImpl(virDomainPtr dom, const char *path, const char *base, goto cleanup; } - device = qemuDiskPathToAlias(vm, path, NULL); + device = qemuDiskPathToAlias(vm, path, &idx); if (!device) { goto cleanup; } @@ -11633,6 +11656,12 @@ qemuDomainBlockJobImpl(virDomainPtr dom, const char *path, const char *base, "this QEMU binary")); goto cleanup; } + if (mode == BLOCK_JOB_PULL && vm->def->disks[idx]->mirror) { + qemuReportError(VIR_ERR_BLOCK_COPY_ACTIVE, + _("disk '%s' already in active block copy job"), + vm->def->disks[idx]->dst); + goto cleanup; + } if (qemuDomainObjBeginJobWithDriver(driver, vm, QEMU_JOB_MODIFY) < 0) goto cleanup; diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c index 857b980..98fa8f8 100644 --- a/src/qemu/qemu_hotplug.c +++ b/src/qemu/qemu_hotplug.c @@ -1721,6 +1721,13 @@ int qemuDomainDetachDiskDevice(struct qemud_driver *driver, detach = vm->def->disks[i]; + if (detach->mirror) { + qemuReportError(VIR_ERR_BLOCK_COPY_ACTIVE, + _("disk '%s' is in an active block copy job"), + detach->dst); + goto cleanup; + } + if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_DEVICES)) { if (virCgroupForDomain(driver->cgroup, vm->def->name, &cgroup, 0) != 0) { qemuReportError(VIR_ERR_INTERNAL_ERROR,