Re: [Qemu-block] [PATCH v23 09/12] Implement new driver for block replication

[Changlong Xie]

On 07/27/2016 12:17 AM, Max Reitz wrote:
> On 26.07.2016 10:15, Changlong Xie wrote:
> > From: Wen Congyang <address@hidden>
> >
> > Signed-off-by: Wen Congyang <address@hidden>
> > Signed-off-by: Changlong Xie <address@hidden>
> > Signed-off-by: Wang WeiWei <address@hidden>
> > Signed-off-by: zhanghailiang <address@hidden>
> > Signed-off-by: Gonglei <address@hidden>
> > ---
> >   block/Makefile.objs |   1 +
> >   block/replication.c | 658 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >   2 files changed, 659 insertions(+)
> >   create mode 100644 block/replication.c
>
> [...]
>
> > diff --git a/block/replication.c b/block/replication.c
> > new file mode 100644
> > index 0000000..ec35348
> > --- /dev/null
> > +++ b/block/replication.c
> > @@ -0,0 +1,658 @@
>
> [...]
>
> > +static void replication_start(ReplicationState *rs, ReplicationMode mode,
> > +                              Error **errp)
> > +{
>
> [...]
>
> > +        /* start backup job now */
> > +        error_setg(&s->blocker,
> > +                   "Block device is in use by internal backup job");
> > +
> > +        top_bs = bdrv_lookup_bs(s->top_id, s->top_id, errp);
>
> I think you should pass NULL instead of errp...
>
> > +        if (!top_bs || !check_top_bs(top_bs, bs)) {
> > +            error_setg(errp, "No top_bs or it is invalid");
>
> ...or if you don't, then you should not call this function if top_bs is
> NULL. Otherwise you'll probably get a failed assertion in error_setv()
> because *errp is not NULL.

Thanks for pointing it out. if top_is is NULL, *errp will be set in 
bdrv_lookup_bs(). Then we'll get failed assertion in error_setv(). Will
fix it.

> > +            reopen_backing_file(s, false, NULL);
> > +            aio_context_release(aio_context);
> > +            return;
> > +        }
> > +        bdrv_op_block_all(top_bs, s->blocker);
> > +        bdrv_op_unblock(top_bs, BLOCK_OP_TYPE_DATAPLANE, s->blocker);
>
> Shouldn't you make sure that top_bs is a root node? The first patch in

Indeed, it should be a root node

> Kevin's "block: Accept node-name in all node level QMP commands" series
> introduces the bdrv_is_root_node() function for that purpose.
>
> Maybe that check should be put into check_top_bs().

I think we just need check top_bs is a root node or not one time before 
stepping in check_top_bs().

if (!top_bs || !bdrv_is_root_node(top_bs) ||
    !check_top_bs(top_bs, bs)) {

> Max
>
> > +
> > +        backup_start("replication-backup", s->secondary_disk->bs,
> > +                     s->hidden_disk->bs, 0, MIRROR_SYNC_MODE_NONE, NULL,
> > +                     BLOCKDEV_ON_ERROR_REPORT, BLOCKDEV_ON_ERROR_REPORT,
> > +                     backup_job_completed, s, NULL, &local_err);
> > +        if (local_err) {
> > +            error_propagate(errp, local_err);
> > +            backup_job_cleanup(s);
> > +            aio_context_release(aio_context);
> > +            return;
> > +        }
> > +        break;