[Libguestfs] [PATCH nbdkit v5 FINAL 10/19] offset: Implement mapping of extents.

[Richard W.M. Jones]

On Tue, Apr 23, 2019 at 12:36:05PM -0500, Eric Blake wrote:
> On 3/28/19 11:18 AM, Richard W.M. Jones wrote:
> > Allows you to safely use nbdkit-offset-filter on top of a plugin
> > supporting extents.
> > ---
> >  filters/offset/offset.c | 36 ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 36 insertions(+)
> > 
> 
> > +
> > +  extents2 = nbdkit_extents_new (offs + offset, real_size - offset);
> > +  if (extents2 == NULL) {
> > +    *err = errno;
> > +    return -1;
> > +  }
> 
> Here, we are careful to set *err.
> 
> > +  if (next_ops->extents (nxdata, count, offs + offset,
> > +                         flags, extents2, err) == -1)
> > +    goto error;
> 
> And here.
> 
> > +
> > +  for (i = 0; i < nbdkit_extents_count (extents2); ++i) {
> > +    e = nbdkit_get_extent (extents2, i);
> > +    e.offset -= offset;
> > +    if (nbdkit_add_extent (extents, e.offset, e.length, e.type) == -1)
> > +      goto error;
> 
> But here, *err remains unchanged. Is this a problem? Should
> nbdkit_add_extent() guarantee that errno is sane on failure (right now,
> it does not)?
> 
> Affects several filters.

Yes I'm pretty certain this is a bug.  I guess because this jumps to
'error:' I copied the previous pattern and thus forgot to set *err ...

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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