Re: [Qemu-devel] [PATCH 1/2] qemu-nbd: Shrink image size by specified offset

["Tomáš Golembiovský" <tgolembi@redhat.com>]

Whops, somehow I completely forgot about this.

On Tue, 20 Sep 2016 09:09:59 -0500
Eric Blake <eblake@redhat.com> wrote:

> On 09/20/2016 04:37 AM, Tomáš Golembiovský wrote:
> 
> [meta-comment]: Your series came through without any threading (you sent
> three threads, instead of patch 1 and 2 being marked In-Reply-To the 0/2
> cover letter).

Thanks for the comment. Unfortunately it was my email client
interfering. It should be better next time.


> > When --offset is set the apparent device size has to be adjusted
> > accordingly. Otherwise client may request read/write beyond the file end
> > which would fail.
> > 
> > Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
> > ---
> >  qemu-nbd.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/qemu-nbd.c b/qemu-nbd.c
> > index 99297a5..629bce1 100644
> > --- a/qemu-nbd.c
> > +++ b/qemu-nbd.c
> > @@ -901,6 +901,13 @@ int main(int argc, char **argv)
> >          exit(EXIT_FAILURE);
> >      }  
> 
> Additional context:
> 
>     off_t dev_offset = 0;
> 
>     off_t fd_size;
> 
> >  
> > +    if (dev_offset >= fd_size) {
> > +        error_report("Offset (%lu) has to be smaller than the image size (%lu)",
> > +                     dev_offset, fd_size);  
> 
> Whoops, this fails to compile on 32-bit platforms.  %lu is not
> necessarily synonymous with off_t values.

After some digging I figured off_t is in fact signed type. That makes
the formatting wrong everywhere. Unfortunately I didn't find any good
definition of the type. Any suggestion what format flag should I use? Or
should I just use a temporary variable of known size for that?


Thanks,

    Tomas


-- 
Tomáš Golembiovský <tgolembi@redhat.com>