Re: [PATCH 1/3] qemu_monitor: introduce new function to get QOM path

[Pavel Hrdina <phrdina@xxxxxxxxxx>]

On 12/16/2014 12:54 AM, John Ferlan wrote:
> On 12/11/2014 10:42 AM, Pavel Hrdina wrote:
> > The search is done recursively only through QOM object that has a type
> > prefixed with "child<" as this indicate that the QOM is a parent for
> > other QOM objects.
> >
> > The usage is that you give known device name with starting path where to
> > search.
> >
> > Signed-off-by: Pavel Hrdina <phrdina@xxxxxxxxxx>
> > ---
> >   src/qemu/qemu_monitor.c | 173 ++++++++++++++++++++++++++++--------------------
> >   1 file changed, 102 insertions(+), 71 deletions(-)
> >
> > diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
> > index c9c84f9..ee4460f 100644
> > --- a/src/qemu/qemu_monitor.c
> > +++ b/src/qemu/qemu_monitor.c
> > @@ -1008,22 +1008,90 @@ qemuMonitorSetOptions(qemuMonitorPtr mon, virJSONValuePtr options)
> >       mon->options = options;
> >   }
> >
> > -/* Search the qom objects for the balloon driver object by it's known name
> > - * of "virtio-balloon-pci".  The entry for the driver will be found in the
> > - * returned 'type' field using the syntax "child<virtio-balloon-pci>".
> > - *
> > - * Once found, check the entry to ensure it has the correct property listed.
> > - * If it does not, then obtaining statistics from qemu will not be possible.
> > - * This feature was added to qemu 1.5.
> > +
> > +/**
> > + * Search the qom objects by it's known name.  The name is compared against
> > + * filed 'type' formatted as 'link<%name>'.
> >    *
> >    * This procedure will be call recursively until found or the qom-list is
> >    * exhausted.
> >    *
> >    * Returns:
> >    *
> > - *   1  - Found
> > - *   0  - Not found still looking
> > + *   0  - Found
> >    *  -1  - Error bail out
> > + *  -2  - Not found
> > + *
> > + * NOTE: This assumes we have already called qemuDomainObjEnterMonitor()
> > + */
> > +static int
> > +qemuMonitorFindObjectPath(qemuMonitorPtr mon,
> > +                          const char *curpath,
> > +                          const char *name,
> > +                          char **path)
> > +{
> > +    ssize_t i, npaths = 0;
> > +    int ret = -2;
> > +    char *nextpath = NULL;
> > +    char *type = NULL;
> > +    qemuMonitorJSONListPathPtr *paths = NULL;
> > +
> > +    if (virAsprintf(&type, "link<%s>", name) < 0)
> > +        return -1;
> > +
> > +    VIR_DEBUG("Searching for '%s' Object Path starting at '%s'", type, curpath);
> > +
> > +    npaths = qemuMonitorJSONGetObjectListPaths(mon, curpath, &paths);
> > +    if (npaths < 0)
> > +        goto cleanup;
> > +
> > +    for (i = 0; i < npaths && ret == -2; i++) {
> > +
> > +        if (STREQ_NULLABLE(paths[i]->type, type)) {
> > +            VIR_DEBUG("Path to '%s' is '%s/%s'", type, curpath, paths[i]->name);
> > +            ret = 0;
> > +            if (virAsprintf(path, "%s/%s", curpath, paths[i]->name) < 0) {
> > +                *path = NULL;
> > +                ret = -1;
> > +            }
> > +            goto cleanup;
> > +        }
> > +
> > +        /* Type entries that begin with "child<" are a branch that can be
> > +         * traversed looking for more entries
> > +         */
> > +        if (paths[i]->type && STRPREFIX(paths[i]->type, "child<")) {
> > +            if (virAsprintf(&nextpath, "%s/%s", curpath, paths[i]->name) < 0) {
> > +                ret = -1;
> > +                goto cleanup;
> > +            }
> > +
> > +            ret = qemuMonitorFindObjectPath(mon, nextpath, name, path);
> > +        }
> > +    }
> > +
> > + cleanup:
> > +    for (i = 0; i < npaths; i++)
> > +        qemuMonitorJSONListPathFree(paths[i]);
> > +    VIR_FREE(paths);
> > +    VIR_FREE(nextpath);
> > +    VIR_FREE(type);
> > +    return ret;
> > +}
> > +
> > +
>
> NIT: You added a /** as the comment opener previously, but not here.

I'll fix that :)

> > +/* Search the qom objects for the balloon driver object by it's known name
> > + * of "virtio-balloon-pci".  The entry for the driver will be found by using
> > + * function "qemuMonitorFindObjectPath".
> > + *
> > + * Once found, check the entry to ensure it has the correct property listed.
> > + * If it does not, then obtaining statistics from QEMU will not be possible.
> > + * This feature was added to QEMU 1.5.
> > + *
> > + * Returns:
> > + *
> > + *   0  - Found
> > + *  -1  - Not found or error
> >    *
> >    * NOTE: This assumes we have already called qemuDomainObjEnterMonitor()
> >    */
> > @@ -1032,14 +1100,13 @@ qemuMonitorFindBalloonObjectPath(qemuMonitorPtr mon,
> >                                    virDomainObjPtr vm,
> >                                    const char *curpath)
> >   {
> > -    ssize_t i, j, npaths = 0, nprops = 0;
> > -    int ret = 0;
> > -    char *nextpath = NULL;
> > -    qemuMonitorJSONListPathPtr *paths = NULL;
> > +    ssize_t i, nprops = 0;
> > +    int ret = -1;
> > +    char *path = NULL;
> >       qemuMonitorJSONListPathPtr *bprops = NULL;
> >
> >       if (mon->balloonpath) {
> > -        return 1;
> > +        return 0;
> >       } else if (mon->ballooninit) {
> >           virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> >                          _("Cannot determine balloon device path"));
> > @@ -1055,70 +1122,34 @@ qemuMonitorFindBalloonObjectPath(qemuMonitorPtr mon,
> >           return -1;
> >       }
> >
> > -    VIR_DEBUG("Searching for Balloon Object Path starting at %s", curpath);
> > -
> > -    npaths = qemuMonitorJSONGetObjectListPaths(mon, curpath, &paths);
> > -    if (npaths < 0)
> > +    if (qemuMonitorFindObjectPath(mon, curpath, "virtio-balloon-pci", &path) < 0)
> >           return -1;
> >
> > -    for (i = 0; i < npaths && ret == 0; i++) {
> > -
> > -        if (STREQ_NULLABLE(paths[i]->type, "link<virtio-balloon-pci>")) {
> > -            VIR_DEBUG("Path to <virtio-balloon-pci> is '%s/%s'",
> > -                      curpath, paths[i]->name);
> > -            if (virAsprintf(&nextpath, "%s/%s", curpath, paths[i]->name) < 0) {
> > -                ret = -1;
> > -                goto cleanup;
> > -            }
> > -
> > -            /* Now look at the each of the property entries to determine
> > -             * whether "guest-stats-polling-interval" exists.  If not,
> > -             * then this version of qemu/kvm does not support the feature.
> > -             */
> > -            nprops = qemuMonitorJSONGetObjectListPaths(mon, nextpath, &bprops);
> > -            if (nprops < 0) {
> > -                ret = -1;
> > -                goto cleanup;
> > -            }
> > -
> > -            for (j = 0; j < nprops; j++) {
> > -                if (STREQ(bprops[j]->name, "guest-stats-polling-interval")) {
> > -                    VIR_DEBUG("Found Balloon Object Path %s", nextpath);
> > -                    mon->balloonpath = nextpath;
> > -                    nextpath = NULL;
> > -                    ret = 1;
> > -                    goto cleanup;
> > -                }
> > -            }
> > -
> > -            /* If we get here, we found the path, but not the property */
> > -            virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> > -                           _("Property 'guest-stats-polling-interval' "
> > -                             "not found on memory balloon driver."));
> > -            ret = -1;
> > +    nprops = qemuMonitorJSONGetObjectListPaths(mon, path, &bprops);
> > +    if (nprops < 0)
> > +        goto cleanup;
> > +
> > +    for (i = 0; i < nprops; i++) {
> > +        if (STREQ(bprops[i]->name, "guest-stats-polling-interval")) {
> > +            VIR_DEBUG("Found Balloon Object Path %s", path);
> > +            mon->balloonpath = path;
> > +            path = NULL;
> > +            ret = 0;
> >               goto cleanup;
> >           }
> > -
> > -        /* Type entries that begin with "child<" are a branch that can be
> > -         * traversed looking for more entries
> > -         */
> > -        if (paths[i]->type && STRPREFIX(paths[i]->type, "child<")) {
> > -            if (virAsprintf(&nextpath, "%s/%s", curpath, paths[i]->name) < 0) {
> > -                ret = -1;
> > -                goto cleanup;
> > -            }
> > -            ret = qemuMonitorFindBalloonObjectPath(mon, vm, nextpath);
> > -        }
> >       }
> >
> > +
> > +    /* If we get here, we found the path, but not the property */
> > +    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> > +                   _("Property 'guest-stats-polling-interval' "
> > +                     "not found on memory balloon driver."));
> > +
> >    cleanup:
> > -    for (i = 0; i < npaths; i++)
> > -        qemuMonitorJSONListPathFree(paths[i]);
> > -    VIR_FREE(paths);
> > -    for (j = 0; j < nprops; j++)
> > -        qemuMonitorJSONListPathFree(bprops[j]);
> > +    for (i = 0; i < nprops; i++)
> > +        qemuMonitorJSONListPathFree(bprops[i]);
> >       VIR_FREE(bprops);
> > -    VIR_FREE(nextpath);
> > +    VIR_FREE(path);
> >       return ret;
> >   }
> >
> > @@ -1660,7 +1691,7 @@ int qemuMonitorSetMemoryStatsPeriod(qemuMonitorPtr mon,
> >           return -1;
> >       }
> >
> > -    if (qemuMonitorFindBalloonObjectPath(mon, mon->vm, "/") == 1) {
> > +    if (qemuMonitorFindBalloonObjectPath(mon, mon->vm, "/") == 0) {
>
> A bit of a bikeshed, but the "/" could be moved into the called function
> - I say this only because in patch 3 you call qemuMonitorFindObjectPath
> with "/".

The reason to have this parameter is that you can pass non root path to
speed up the search.

> Could probably also just pass 'mon' and deref 'mon->vm' in the called
> routine.

This is a good point, I'll fix that.

Thanks for review

Pavel

> ACK,
>
> John
>
> >           ret = qemuMonitorJSONSetMemoryStatsPeriod(mon, mon->balloonpath,
> >                                                     period);
> >       }

--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list