Re: [Qemu-devel] [PATCH v4 7/7] block: Allow backup on referenced named BlockDriverState

[Fam Zheng]

On 2013年11月25日 19:23, Kevin Wolf wrote:
> Am 22.11.2013 um 06:24 hat Fam Zheng geschrieben:
> > Drive backup is a read only operation on source bs. We want to allow
> > this specific case to enable image-fleecing. Note that when
> > image-fleecing job starts, the job still add its blocker to source bs,
> > and any other operation on it will be blocked by that.
> >
> > Signed-off-by: Fam Zheng <address@hidden>
> > ---
> >   block.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/block.c b/block.c
> > index a5da656..d30be51 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -1179,6 +1179,8 @@ int bdrv_open(BlockDriverState *bs, const char *filename, 
> > QDict *options,
> >                              "device is used as backing hd of '%s'",
> >                              bs->device_name);
> >                   bdrv_op_block_all(bs->backing_hd, bs->backing_blocker);
> > +                bdrv_op_unblock(bs->backing_hd, BLOCK_OP_TYPE_BACKUP,
> > +                                bs->backing_blocker);
> >                   pstrcpy(bs->backing_file, sizeof(bs->backing_file),
> >                           bs->backing_hd->filename);
> >                   pstrcpy(bs->backing_format, sizeof(bs->backing_format),
>
> We probably need separate blockers for "can be a backup source" and "can
> be a backup target". Because I think this allows using it as a
> read-write target as well, which was not intended.

Yes. Will do it.

> Do we need to cover this in other parts of the code as well, like when
> adding a new BDS during external snapshot creation?

Does it have a name? If not I think we are safe there.

Fam