[libvirt] [PATCHv2 13/7] snapshot: implement snapshot children listing in vbox

[Matthias Bolte]

2011/10/7 Eric Blake <eblake at redhat.com>:
> Adding this for VBox was a bit harder than for ESX, but the same
> principles apply for starting the traversal at a known point
> rather than covering the entire hierarchy.
>
> * src/vbox/vbox_tmpl.c (vboxCountDescendants)
> (vboxDomainSnapshotNumChildren)
> (vboxDomainSnapshotListChildrenNames): New functions.
> ---
>
> Changes in v2: avoid leaking snapshot, and fix recursive children
> names to get through loop properly by transferring initial snapshot
> into loop then skipping that element while grabbing names.
>
> Still untested from my end, but hopefully does better.
>
>  src/vbox/vbox_tmpl.c |  213 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 213 insertions(+), 0 deletions(-)
>
> diff --git a/src/vbox/vbox_tmpl.c b/src/vbox/vbox_tmpl.c
> index c74d2cf..84a4fca 100644
> --- a/src/vbox/vbox_tmpl.c
> +++ b/src/vbox/vbox_tmpl.c

> +static int
> +vboxDomainSnapshotListChildrenNames(virDomainSnapshotPtr snapshot,
> +                                    char **names,
> +                                    int nameslen,
> +                                    unsigned int flags)
> +{
> +    virDomainPtr dom = snapshot->domain;
> +    VBOX_OBJECT_CHECK(dom->conn, int, -1);
> +    vboxIID iid = VBOX_IID_INITIALIZER;
> +    IMachine *machine = NULL;
> +    ISnapshot *snap = NULL;
> +    nsresult rc;
> +    ISnapshot **snapshots = NULL;
> +    PRUint32 count = 0;
> +    int i;
> +    vboxArray children = VBOX_ARRAY_INITIALIZER;
> +
> +    virCheckFlags(VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS |
> +                  VIR_DOMAIN_SNAPSHOT_LIST_METADATA, -1);
> +
> +    vboxIIDFromUUID(&iid, dom->uuid);
> +    rc = VBOX_OBJECT_GET_MACHINE(iid.value, &machine);
> +    if (NS_FAILED(rc)) {
> +        vboxError(VIR_ERR_NO_DOMAIN, "%s",
> +                  _("no domain with matching UUID"));
> +        goto cleanup;
> +    }
> +
> +    if (!(snap = vboxDomainSnapshotGet(data, dom, machine, snapshot->name)))
> +        goto cleanup;
> +
> +    if (!nameslen || (flags & VIR_DOMAIN_SNAPSHOT_LIST_METADATA)) {
> +        ret = 0;
> +        goto cleanup;
> +    }
> +
> +    /* Over-allocates, but this is the easiest way to do things */
> +    rc = machine->vtbl->GetSnapshotCount(machine, &count);
> +    if (NS_FAILED(rc)) {
> +        vboxError(VIR_ERR_INTERNAL_ERROR,
> +                  _("could not get snapshot count for domain %s"),
> +                  dom->name);
> +        goto cleanup;
> +    }
> +
> +    if (VIR_ALLOC_N(snapshots, count) < 0) {
> +        virReportOOMError();
> +        goto cleanup;
> +    }
> +
> +    rc = vboxArrayGet(&children, snap, snap->vtbl->GetChildren);
> +    if (NS_FAILED(rc)) {
> +        vboxError(VIR_ERR_INTERNAL_ERROR,
> +                  "%s", _("could not get children snapshots"));
> +        goto cleanup;
> +    }
> +
> +    if (flags & VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS) {
> +        int top = children.count;
> +        int next;
> +
> +        snapshots[0] = snap;
> +        snap = NULL;
> +        for (next = 0; next < count; next++) {
> +            if (!snapshots[next])
> +                break;
> +            rc = vboxArrayGet(&children, snapshots[next],
> +                              snapshots[next]->vtbl->GetChildren);
> +            if (NS_FAILED(rc)) {
> +                vboxError(VIR_ERR_INTERNAL_ERROR,
> +                          "%s", _("could not get children snapshots"));
> +                goto cleanup;
> +            }
> +            for (i = 0; i < children.count; i++) {
> +                ISnapshot *child = children.items[i];
> +                if (!child)
> +                    continue;
> +                if (top == count) {
> +                    vboxError(VIR_ERR_INTERNAL_ERROR,
> +                              _("unexpected number of snapshots > %u"), count);
> +                    vboxArrayRelease(&children);
> +                    goto cleanup;
> +                }
> +                VBOX_ADDREF(child);
> +                snapshots[top++] = child;
> +            }
> +            vboxArrayRelease(&children);
> +        }
> +        count = top - 1;
> +    } else {
> +        count = children.count;
> +    }
> +
> +    for (i = 0; i < nameslen; i++) {
> +        PRUnichar *nameUtf16;
> +        char *name;
> +        int j = i + !!(flags & VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS);
> +
> +        if (i >= count)
> +            break;
> +
> +        rc = snapshots[j]->vtbl->GetName(snapshots[j], &nameUtf16);

Still a segfault here because snapshots[0] is NULL. Also I think this
logic is too complicated here. Are we really afraid of a stack
overflow because of a domain with many snapshots that we need to avoid
a recursive solution?

You already implemented vboxCountDescendants recursively, I'd suggest
to do the same here too.

I attached a patch to be applied on top of this one that does this and
works for me.

ACK with the attached patch applied.

-- 
Matthias Bolte
http://photron.blogspot.com
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