Am 13.10.2015 um 03:53 hat Jeff Cody geschrieben:
> On Fri, Oct 09, 2015 at 02:15:32PM +0200, Kevin Wolf wrote:
> > This is the final step in converting all of the BlockDriverState
> > pointers that block drivers use to BdrvChild.
> >
> > After this patch, bs->children contains the full list of child nodes
> > that are referenced by a given BDS, and these children are only
> > referenced through BdrvChild, so that updating the pointer in there is
> > enough for changing edges in the graph.
> >
> > Signed-off-by: Kevin Wolf <kw...@redhat.com>
> > ---
> > block.c | 105
> > +++++++++++++++++++++++-----------------------
> > block/io.c | 24 +++++------
> > block/mirror.c | 6 +--
> > block/qapi.c | 8 ++--
> > block/qcow.c | 4 +-
> > block/qcow2-cluster.c | 4 +-
> > block/qcow2.c | 6 +--
> > block/qed.c | 12 +++---
> > block/stream.c | 8 ++--
> > block/vmdk.c | 21 +++++-----
> > block/vvfat.c | 6 +--
> > blockdev.c | 4 +-
> > include/block/block_int.h | 12 ++++--
> > qemu-img.c | 4 +-
> > 14 files changed, 115 insertions(+), 109 deletions(-)
> >
>
> [...]
>
> > diff --git a/include/block/block_int.h b/include/block/block_int.h
> > index 98936c9..90971c0 100644
> > --- a/include/block/block_int.h
> > +++ b/include/block/block_int.h
> > @@ -378,8 +378,7 @@ struct BlockDriverState {
> > QDict *full_open_options;
> > char exact_filename[PATH_MAX];
> >
> > - BlockDriverState *backing_hd;
> > - BdrvChild *backing_child;
> > + BdrvChild *backing;
> > BdrvChild *file;
> >
> > NotifierList close_notifiers;
> > @@ -458,6 +457,11 @@ struct BlockDriverState {
> > NotifierWithReturn write_threshold_notifier;
> > };
> >
> > +static inline BlockDriverState *backing_bs(BlockDriverState *bs)
> > +{
> > + return bs->backing ? bs->backing->bs : NULL;
> > +}
> > +
>
> Is there a good guideline regarding when you prefer backing_bs() to be
> used, over accessing bs->backing->bs directly? There seems to be a
> lot of mixed usage left in this patch, and I'm not sure if I am just
> missing the intended distinction.
Essentially, I'm using backing_bs() whenever bs->backing could be NULL,
because bs->backing->bs would segfault then. When I know that it's not
NULL, I prefer the direct access.
Kevin
