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Re: [libvirt] [PATCH 3/5] snapshot: refactor virsh snapshot parent computation



On Sat, Sep 24, 2011 at 06:30:04PM -0600, Eric Blake wrote:
> Make parent computation reusable, using virDomainSnapshotGetParent
> when possible.
> 
> * tools/virsh.c (vshGetSnapshotParent): New helper.
> (cmdSnapshotParent): Use it.
> ---
>  tools/virsh.c |   66 ++++++++++++++++++++++++++++++++++++++++++++-------------
>  1 files changed, 51 insertions(+), 15 deletions(-)
> 
> diff --git a/tools/virsh.c b/tools/virsh.c
> index 7b0533d..035b209 100644
> --- a/tools/virsh.c
> +++ b/tools/virsh.c
> @@ -246,6 +246,8 @@ typedef struct __vshControl {
>      char *historyfile;          /* readline history file name */
>      bool useGetInfo;            /* must use virDomainGetInfo, since
>                                     virDomainGetState is not supported */
> +    bool useSnapshotGetXML;     /* must use virDomainSnapshotGetXMLDesc, since
> +                                   virDomainSnapshotGetParent is missing */
>  } __vshControl;
> 
>  typedef struct vshCmdGrp {
> @@ -613,6 +615,7 @@ vshReconnect(vshControl *ctl)
>          vshError(ctl, "%s", _("Reconnected to the hypervisor"));
>      disconnected = 0;
>      ctl->useGetInfo = false;
> +    ctl->useSnapshotGetXML = false;
>  }
> 
>  /* ---------------
> @@ -760,6 +763,7 @@ cmdConnect(vshControl *ctl, const vshCmd *cmd)
>      ctl->name = vshStrdup(ctl, name);
> 
>      ctl->useGetInfo = false;
> +    ctl->useSnapshotGetXML = false;
>      ctl->readonly = ro;
> 
>      ctl->conn = virConnectOpenAuth(ctl->name, virConnectAuthPtrDefault,
> @@ -12967,6 +12971,52 @@ cleanup:
>      return ret;
>  }
> 
> +/* Helper function to get the name of a snapshot's parent.  Caller
> + * must free the result.  */
> +static char *
> +vshGetSnapshotParent(vshControl *ctl, virDomainSnapshotPtr snapshot)
> +{
> +    virDomainSnapshotPtr parent = NULL;
> +    char *xml = NULL;
> +    xmlDocPtr xmldoc = NULL;
> +    xmlXPathContextPtr ctxt = NULL;
> +    char *parent_name = NULL;
> +
> +    /* Try new API, since it is faster. */
> +    if (!ctl->useSnapshotGetXML) {
> +        parent = virDomainSnapshotGetParent(snapshot, 0);
> +        if (parent) {
> +            /* API works, and virDomainSnapshotGetName will succeed */
> +            parent_name = vshStrdup(ctl, virDomainSnapshotGetName(snapshot));
> +            goto cleanup;
> +        }
> +        if (last_error->code == VIR_ERR_NO_DOMAIN_SNAPSHOT) {
> +            /* API works, and we found a root with no parent */
> +            goto cleanup;
> +        }
> +        /* API didn't work, fall back to XML scraping. */
> +        ctl->useSnapshotGetXML = true;
> +    }
> +
> +    xml = virDomainSnapshotGetXMLDesc(snapshot, 0);
> +    if (!xml)
> +        goto cleanup;
> +
> +    xmldoc = virXMLParseStringCtxt(xml, _("(domain_snapshot)"), &ctxt);
> +    if (!xmldoc)
> +        goto cleanup;
> +
> +    parent_name = virXPathString("string(/domainsnapshot/parent/name)", ctxt);
> +
> +cleanup:
> +    if (parent)
> +        virDomainSnapshotFree(parent);
> +    xmlXPathFreeContext(ctxt);
> +    xmlFreeDoc(xmldoc);
> +    VIR_FREE(xml);
> +    return parent_name;
> +}
> +
>  /*
>   * "snapshot-list" command
>   */
> @@ -13220,10 +13270,7 @@ cmdSnapshotParent(vshControl *ctl, const vshCmd *cmd)
>      bool ret = false;
>      const char *name = NULL;
>      virDomainSnapshotPtr snapshot = NULL;
> -    char *xml = NULL;
>      char *parent = NULL;
> -    xmlDocPtr xmldoc = NULL;
> -    xmlXPathContextPtr ctxt = NULL;
> 
>      if (!vshConnectionUsability(ctl, ctl->conn))
>          goto cleanup;
> @@ -13239,15 +13286,7 @@ cmdSnapshotParent(vshControl *ctl, const vshCmd *cmd)
>      if (snapshot == NULL)
>          goto cleanup;
> 
> -    xml = virDomainSnapshotGetXMLDesc(snapshot, 0);
> -    if (!xml)
> -        goto cleanup;
> -
> -    xmldoc = virXMLParseStringCtxt(xml, _("(domain_snapshot)"), &ctxt);
> -    if (!xmldoc)
> -        goto cleanup;
> -
> -    parent = virXPathString("string(/domainsnapshot/parent/name)", ctxt);
> +    parent = vshGetSnapshotParent(ctl, snapshot);
>      if (!parent)
>          goto cleanup;
> 
> @@ -13257,9 +13296,6 @@ cmdSnapshotParent(vshControl *ctl, const vshCmd *cmd)
> 
>  cleanup:
>      VIR_FREE(parent);
> -    xmlXPathFreeContext(ctxt);
> -    xmlFreeDoc(xmldoc);
> -    VIR_FREE(xml);
>      if (snapshot)
>          virDomainSnapshotFree(snapshot);
>      if (dom)

  Okay, that works even if one reopen a different connection in shell mode

ACK,

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/


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