Re: [PATCH 2/3] xfsrestore: stobj_unpack_sessinfo cleanup

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Sep 29, 2022 at 09:28:24AM +1000, Donald Douwsma wrote:
> 
> 
> On 29/09/2022 09:12, Donald Douwsma wrote:
> > 
> > 
> > On 29/09/2022 01:23, Darrick J. Wong wrote:
> > > On Wed, Sep 28, 2022 at 03:53:06PM +1000, Donald Douwsma wrote:
> > > > stobj_unpack_sessinfo should be the reverse of stobj_pack_sessinfo, make
> > > > this clearer with respect to the session header and streams processing.
> > > > 
> > > > signed-off-by: Donald Douwsma <ddouwsma@redhat.com>
> > > > ---
> > > >   inventory/inv_stobj.c | 13 +++++++------
> > > >   1 file changed, 7 insertions(+), 6 deletions(-)
> > > > 
> > > > diff --git a/inventory/inv_stobj.c b/inventory/inv_stobj.c
> > > > index 5075ee4..521acff 100644
> > > > --- a/inventory/inv_stobj.c
> > > > +++ b/inventory/inv_stobj.c
> > > > @@ -1065,25 +1065,26 @@ stobj_unpack_sessinfo(
> > > >           return BOOL_FALSE;
> > > >       }
> > > > +    /* get the seshdr and then, the remainder of the session */
> > > >       xlate_invt_seshdr((invt_seshdr_t *)p, (invt_seshdr_t *)tmpbuf, 1);
> > > >       bcopy(tmpbuf, p, sizeof(invt_seshdr_t));
> > > > -
> > > > -    /* get the seshdr and then, the remainder of the session */
> > > >       s->seshdr = (invt_seshdr_t *)p;
> > > >       s->seshdr->sh_sess_off = -1;
> > > >       p += sizeof(invt_seshdr_t);
> > > > -
> > > >       xlate_invt_session((invt_session_t *)p, (invt_session_t
> > > > *)tmpbuf, 1);
> > > >       bcopy (tmpbuf, p, sizeof(invt_session_t));
> > > >       s->ses = (invt_session_t *)p;
> > > >       p += sizeof(invt_session_t);
> > > >       /* the array of all the streams belonging to this session */
> > > > -    xlate_invt_stream((invt_stream_t *)p, (invt_stream_t *)tmpbuf, 1);
> > > > -    bcopy(tmpbuf, p, sizeof(invt_stream_t));
> > > >       s->strms = (invt_stream_t *)p;
> > > > -    p += s->ses->s_cur_nstreams * sizeof(invt_stream_t);
> > > > +    for (i = 0; i < s->ses->s_cur_nstreams; i++) {
> > > > +        xlate_invt_stream((invt_stream_t *)p,
> > > 
> > > Nit: trailing whitespace                        here ^
> > 
> > nod
> > 
> > > 
> > > > +                  (invt_stream_t *)tmpbuf, 1);
> > > > +        bcopy(tmpbuf, p, sizeof(invt_stream_t));
> > > > +        p += sizeof(invt_stream_t);
> > > 
> > > Ok, so we translate p into tmpbuf, then bcopy tmpbuf back to p.  That
> > > part makes sense, but I am puzzled by what stobj_pack_sessinfo does:
> > > 
> > >     for (i = 0; i < ses->s_cur_nstreams; i++) {
> > >         xlate_invt_stream(strms, (invt_stream_t *)sesbuf, 1);
> > >         sesbuf += sizeof(invt_stream_t);
> > >     }
> > > 
> > > Why isn't that callsite xlate_invt_stream(&strms[i], ...); ?
> > 
> > Thanks! Yes, that's wrong, like the existing code it only worked/works
> > because there's only ever one stream. From the manpage "The third level
> > is media stream (currently only one  stream is supported)". Will fix.
> 
> Or should I just drop this clean-up? I think what I'm saying is right,
> but its a clean-up for a feature that cant be used. I doubt anyone is
> going to add multiple stream support now, whatever that was intended
> for.

I don't know.  On the one hand I could see an argument for at least
being able to restore multiple streams, but then the dump program has
been screwing that up for years and nobody noticed.  I can't tell from
the source code what shape the multistream support is in, so I guess you
have some research to do? <shrug>  I suppose you could see what happens
if you try to set up multiple streams, but I have no idea ... what that
means.

Sorry that's a nonanswer. :(

--D

> 
> > 
> > > 
> > > --D
> > > 
> > > > +    }
> > > >       /* all the media files */
> > > >       s->mfiles = (invt_mediafile_t *)p;
> > > > -- 
> > > > 2.31.1
> > > > 
> > > 
>