Re: [Qemu-devel] [PATCH V8 08/20] block: add filter for vm snapshot in bdrv_query_snapshot_info_list()

[Wenchao Xia]

于 2013-3-9 6:55, Eric Blake 写道:
> On 03/06/2013 11:07 PM, Wenchao Xia wrote:
> >    This patch adds a parameter to tell whether return valid snapshots
> > for whole VM only.
> >
> > Signed-off-by: Wenchao Xia <address@hidden>
> > ---
> >   block/qapi.c         |   39 +++++++++++++++++++++++++++++++++++++--
> >   include/block/qapi.h |    1 +
> >   qemu-img.c           |    3 ++-
> >   3 files changed, 40 insertions(+), 3 deletions(-)
>
> > + * @sn: snapshot info need to be checked.
>
> s/need //
  OK.

> > + * return 0 if valid, it means load_vmstate() for it could succeed.
>
> Reads awkwardly; how about:
>
> it means load_vmstate() could load that snapshot.
  I forgot it may not have vmstate() but only only block snapshot,
It should be:
   return 0 if valid, it means the snapshot is consistent for the VM.

> > + */
> > +static int snapshot_filter_vm(const QEMUSnapshotInfo *sn, BlockDriverState *bs)
> > +{
> > +    BlockDriverState *bs1 = NULL;
> > +    QEMUSnapshotInfo s, *sn_info = &s;
> > +    int ret = 0;
> > +
> > +    /* Check logic is connected with load_vmstate():
> > +       Only check the devices that can snapshot, other devices that can't
> > +       take snapshot, for example, readonly ones, will be ignored in
> > +       load_vmstate(). */
> > +    while ((bs1 = bdrv_next(bs1))) {
> > +        if (bdrv_can_snapshot(bs1) && bs1 != bs) {
> > +            ret = bdrv_snapshot_find(bs1, sn_info, sn->id_str, NULL);
> > +            if (ret < 0) {
> > +                ret = -1;
>
> This function only returns 0 or -1...
  OK, it should be bool.

> > +/* return 0 on success, and @p_list will be set only on success. If
> > +   @vm_snapshot is true, only the snapshot valid for whole vm will be got. */
>
> grammar
>
> If @vm_snapshot is true, limit the results to snapshots valid for the
> whole vm.
  Looks better, thanks.

> > -
> > +        if (vm_snapshot && snapshot_filter_vm(&sn_tab[i], bs)) {
>
> ...yet you are only ever calling it in a boolean context.  Would it be
> smarter to have the function return bool (true for valid vm snapshot,
> false if the image snapshot is not usable as a vm snapshot)?
>
> Also, it might be nicer to name it snapshot_valid_for_vm, as in:
>
> if (vm_snapshot && !snapshot_valid_for_vm(...)) {
>      continue;
> }
  OK.

>


--
Best Regards

Wenchao Xia