Re: [Qemu-devel] [PATCH v3 07/22] qcow2: Helper function for refcount modification

[Max Reitz]

On 2014-11-28 at 12:11, Stefan Hajnoczi wrote:
> On Thu, Nov 20, 2014 at 06:06:23PM +0100, Max Reitz wrote:
> > @@ -1711,7 +1746,7 @@ static int calculate_refcounts(BlockDriverState *bs, 
> > BdrvCheckResult *res,
> >   static void compare_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
> >                                 BdrvCheckMode fix, bool *rebuild,
> >                                 int64_t *highest_cluster,
> > -                              uint16_t *refcount_table, int64_t nb_clusters)
> > +                              void *refcount_table, int64_t nb_clusters)
> >   {
> >       BDRVQcowState *s = bs->opaque;
> >       int64_t i, refcount1, refcount2;
> An -ERANGE qcow2_get_refcount() return value is treated as a check error
> here and we won't be able to rebuild the refcount blocks:
>
>    refcount1 = qcow2_get_refcount(bs, i);
>    if (refcount1 < 0) {
>        fprintf(stderr, "Can't get refcount for cluster %" PRId64 ": %s\n",
>            i, strerror(-refcount1));
>        res->check_errors++;
>        continue;
>    }
>
> We should allow rebuilding refcount blocks, -ERANGE is just another
> corrupted refcount.

Right, hopefully this will be fixed by implementing your proposal for 
changing "uint64_t qcow2_get_refcount(...)" to "int 
qcow2_get_refcount(..., uint64_t *)" etc..

Max