Re: [libvirt] [PATCHv3 13/43] snapshot: prevent stranding snapshot data on domain destruction

Just as leaving managed save metadata behind can cause problems when creating a new domain that happens to collide with the name of the just-deleted domain, the same is true of leaving any snapshot metadata behind. For safety sake, extend the semantic change of commit b26a9fa9 to also cover snapshot metadata as a reason to reject losing the last reference to a domain (undefine on an inactive, or shutdown/destroy on a transient). The caller must first take care of snapshots, possible via the existing virDomainSnapshotDelete. This also documents some new flags that hypervisors can choose to support to shortcuts taking care of the metadata as part of the shutdown process; however, nontrivial driver support for these flags will be deferred to future patches. Note that ESX and VBox can never be transient; therefore, they do not have to affect shutdown/destroy (the persistent domain still remains); likewise they never store snapshot metadata, so one of the two flags is trivial. The bulk of the nontrivial work remaining is thus in the qemu driver. * include/libvirt/libvirt.h.in (VIR_DOMAIN_UNDEFINE_SNAPSHOTS) (VIR_DOMAIN_DESTROY_SNAPSHOTS): New flags. * src/libvirt.c (virDomainUndefine, virDomainUndefineFlags) (virDomainDestroy, virDomainDestroyFlags, virDomainShutdown): Document new limitations and flags. * src/esx/esx_driver.c (esxDomainUndefineFlags): Enforce the limitations. * src/vbox/vbox_tmpl.c (vboxDomainUndefineFlags): Likewise. * src/qemu/qemu_driver.c (qemuDomainUndefineFlags) (qemuDomainShutdown, qemuDomainDestroyFlags): Likewise. --- include/libvirt/libvirt.h.in | 25 ++++++++++++++++++--- src/esx/esx_driver.c | 11 ++++++++- src/libvirt.c | 47 +++++++++++++++++++++++++++++++++++------ src/qemu/qemu_driver.c | 27 ++++++++++++++++++++++++ src/vbox/vbox_tmpl.c | 11 ++++++++- 5 files changed, 106 insertions(+), 15 deletions(-) diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in index 20fdbdf..36f1b34 100644 --- a/include/libvirt/libvirt.h.in +++ b/include/libvirt/libvirt.h.in @@ -919,10 +919,20 @@ virConnectPtr virDomainGetConnect (virDomainPtr domain); * Domain creation and destruction */ -/* - * typedef enum { - * } virDomainDestroyFlagsValues; + +/* Counterparts to virDomainUndefineFlagsValues, but note that running + * domains have no managed save data, so no flag is provided for that. */ +typedef enum { + /* VIR_DOMAIN_DESTROY_MANAGED_SAVE = (1 << 0), */ /* Reserved */ + VIR_DOMAIN_DESTROY_SNAPSHOTS_METADATA = (1 << 1), /* If last use of domain, + then also remove any + snapshot metadata */ + VIR_DOMAIN_DESTROY_SNAPSHOTS_FULL = (1 << 2), /* If last use of domain, + then also remove any + snapshot data */ +} virDomainDestroyFlagsValues; + virDomainPtr virDomainCreateXML (virConnectPtr conn, const char *xmlDesc, unsigned int flags); @@ -1240,7 +1250,14 @@ virDomainPtr virDomainDefineXML (virConnectPtr conn, int virDomainUndefine (virDomainPtr domain); typedef enum { - VIR_DOMAIN_UNDEFINE_MANAGED_SAVE = (1 << 0), + VIR_DOMAIN_UNDEFINE_MANAGED_SAVE = (1 << 0), /* Also remove any + managed save */ + VIR_DOMAIN_UNDEFINE_SNAPSHOTS_METADATA = (1 << 1), /* If last use of domain, + then also remove any + snapshot metadata */ + VIR_DOMAIN_UNDEFINE_SNAPSHOTS_FULL = (1 << 2), /* If last use of domain, + then also remove any + snapshot data */ /* Future undefine control flags should come here. */ } virDomainUndefineFlagsValues;