Re: [Qemu-devel] [PATCH] vhost-user-bridge: fix iov_restore_front() warning

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 07, 2017 at 07:00:46PM +0000, Marc-André Lureau wrote:
> Hi, Michael, could you pick this patch?
> 
> thanks

OK. Pls cc me on patches you want me to review.

> On Fri, Jun 2, 2017 at 12:26 PM Marc-André Lureau <
> marcandre.lureau@redhat.com> wrote:
> 
> >   CC      tests/vhost-user-bridge.o
> > /home/dgilbert/git/qemu-world3/tests/vhost-user-bridge.c:228:23: warning:
> > variables 'front' and 'iov' used in loop condition not modified in loop
> > body [-Wfor-loop-analysis]
> >     for (cur = front; front != iov; cur++) {
> >                       ^~~~~    ~~~
> > 1 warning generated.
> >
> > Fix the loop, document the function, and fix some related assert().
> >
> > In practice, the loop bug was harmless because the front sg buffer is
> > enough to discard/restore the header size.
> >
> > Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> >  tests/vhost-user-bridge.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
> > index 8618c20d53..1e5b5ca3da 100644
> > --- a/tests/vhost-user-bridge.c
> > +++ b/tests/vhost-user-bridge.c
> > @@ -220,12 +220,18 @@ vubr_handle_tx(VuDev *dev, int qidx)
> >      free(elem);
> >  }
> >
> > +
> > +/* this function reverse the effect of iov_discard_front() it must be
> > + * called with 'front' being the original struct iovec and 'bytes'
> > + * being the number of bytes you shaved off
> > + */
> >  static void
> >  iov_restore_front(struct iovec *front, struct iovec *iov, size_t bytes)
> >  {
> >      struct iovec *cur;
> >
> > -    for (cur = front; front != iov; cur++) {
> > +    for (cur = front; cur != iov; cur++) {
> > +        assert(bytes >= cur->iov_len);
> >          bytes -= cur->iov_len;
> >      }
> >
> > @@ -302,7 +308,8 @@ vubr_backend_recv_cb(int sock, void *ctx)
> >              }
> >              iov_from_buf(sg, elem->in_num, 0, &hdr, sizeof hdr);
> >              total += hdrlen;
> > -            assert(iov_discard_front(&sg, &num, hdrlen) == hdrlen);
> > +            ret = iov_discard_front(&sg, &num, hdrlen);
> > +            assert(ret == hdrlen);
> >          }
> >
> >          struct msghdr msg = {
> > --
> > 2.13.0.91.g00982b8dd
> >
> >
> > --
> Marc-André Lureau