[libvirt] [PATCHv2] qemu: don't leak vm on failure

[Osier Yang]

On 07/09/13 01:55, Eric Blake wrote:
> Failure to attach to a domain during 'virsh qemu-attach' left
> the list of domains in an odd state:
>
> $ virsh qemu-attach 4176
> error: An error occurred, but the cause is unknown
>
> $ virsh list --all
>   Id    Name                           State
> ----------------------------------------------------
>   2     foo                            shut off
>
> $ virsh qemu-attach 4176
> error: Requested operation is not valid: domain is already active as 'foo'
>
> $ virsh undefine foo
> error: Failed to undefine domain foo
> error: Requested operation is not valid: cannot undefine transient domain
>
> $ virsh shutdown foo
> error: Failed to shutdown domain foo
> error: invalid argument: monitor must not be NULL
>
> It all stems from leaving the list of domains unmodified on
> the initial failure; we should follow the lead of createXML
> which removes vm on failure (the actual initial failure still
> needs to be fixed in a later patch, but at least this patch
> gets us to the point where we aren't getting stuck with an
> unremovable "shut off" transient domain).
>
> While investigating, I also found a leak in qemuDomainCreateXML;
> the two functions should behave similarly.  Note that there are
> still two unusual paths: if dom is not allocated, the user will
> see an OOM error even though the vm remains registered (but oom
> errors already indicate tricky cleanup); and if the vm starts
> and then quits again all before the job ends, it is possible
> to return a non-NULL dom even though the dom will no longer be
> useful for anything (but this at least lets the user know their
> short-lived vm ran).
>
> * src/qemu/qemu_driver.c (qemuDomainCreateXML): Don't leak vm on
> failure to obtain job.
> (qemuDomainQemuAttach): Match cleanup of qemuDomainCreateXML.
>
> Signed-off-by: Eric Blake <eblake at redhat.com>
> ---
>
> v1 was discussed here: https://www.redhat.com/archives/libvir-list/2013-September/msg00362.html
> changes since then: plug another leak of vm, and clean up some style.
> Expand the commit message to explain unusual paths.
>
>   src/qemu/qemu_driver.c | 31 +++++++++++++++++++------------
>   1 file changed, 19 insertions(+), 12 deletions(-)
>
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index e37fe33..6dafa2b 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -1602,8 +1602,11 @@ static virDomainPtr qemuDomainCreateXML(virConnectPtr conn,
>
>       def = NULL;
>
> -    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
> -        goto cleanup; /* XXXX free the 'vm' we created ? */
> +    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0) {
> +        qemuDomainRemoveInactive(driver, vm);
> +        vm = NULL;
> +        goto cleanup;
> +    }
>
>       if (qemuProcessStart(conn, driver, vm, NULL, -1, NULL, NULL,
>                            VIR_NETDEV_VPORT_PROFILE_OP_CREATE,
> @@ -1631,10 +1634,10 @@ static virDomainPtr qemuDomainCreateXML(virConnectPtr conn,
>       virDomainAuditStart(vm, "booted", true);
>
>       dom = virGetDomain(conn, vm->def->name, vm->def->uuid);
> -    if (dom) dom->id = vm->def->id;
> +    if (dom)
> +        dom->id = vm->def->id;
>
> -    if (vm &&
> -        qemuDomainObjEndJob(driver, vm) == 0)
> +    if (qemuDomainObjEndJob(driver, vm) == 0)
>           vm = NULL;
>
>   cleanup:
> @@ -13630,34 +13633,38 @@ static virDomainPtr qemuDomainQemuAttach(virConnectPtr conn,
>
>       def = NULL;
>
> -    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
> +    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0) {
> +        qemuDomainRemoveInactive(driver, vm);
> +        vm = NULL;
>           goto cleanup;
> +    }
>
>       if (qemuProcessAttach(conn, driver, vm, pid,
>                             pidfile, monConfig, monJSON) < 0) {
> +        if (qemuDomainObjEndJob(driver, vm) > 0)

Just realized that qemuDomainObjEndJob returns bool value. We may need a
follow up patch to clean it up.

> +            qemuDomainRemoveInactive(driver, vm);
> +        vm = NULL;
>           monConfig = NULL;
> -        goto endjob;
> +        goto cleanup;
>       }
>
>       monConfig = NULL;
>
>       dom = virGetDomain(conn, vm->def->name, vm->def->uuid);
> -    if (dom) dom->id = vm->def->id;
> +    if (dom)
> +        dom->id = vm->def->id;
>
> -endjob:
>       if (qemuDomainObjEndJob(driver, vm) == 0) {
>

ACK with "{" removed.