Re: [Qemu-devel] [PATCH v3 19/19] block: look for zero blocks in bs->file

[Paolo Bonzini <pbonzini@redhat.com>]

----- Original Message -----
> From: "Kevin Wolf" <kwolf@redhat.com>
> To: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: qemu-devel@nongnu.org, stefanha@redhat.com, eblake@redhat.com, pl@kamp.de
> Sent: Wednesday, July 31, 2013 11:21:27 AM
> Subject: Re: [PATCH v3 19/19] block: look for zero blocks in bs->file
> 
> Am 25.07.2013 um 16:23 hat Paolo Bonzini geschrieben:
> > Reviewed-by: Eric Blake <eblake@redhat.com>
> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> >  block.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/block.c b/block.c
> > index 8738937..1493f22 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -2991,7 +2991,7 @@ static int64_t coroutine_fn
> > bdrv_co_get_block_status(BlockDriverState *bs,
> >                                                       int nb_sectors, int
> >                                                       *pnum)
> >  {
> >      int64_t n;
> > -    int64_t ret;
> > +    int64_t ret, ret2;
> >  
> >      if (sector_num >= bs->total_sectors) {
> >          *pnum = 0;
> > @@ -3017,6 +3017,14 @@ static int64_t coroutine_fn
> > bdrv_co_get_block_status(BlockDriverState *bs,
> >          ret |= BDRV_BLOCK_ZERO;
> >      }
> >  
> > +    if (bs->file &&
> > +        (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
> > +        (ret & BDRV_BLOCK_OFFSET_VALID)) {
> > +        ret2 = bdrv_co_get_block_status(bs->file, ret >> BDRV_SECTOR_BITS,
> > +                                        *pnum, pnum);
> 
> Here the error check is missing, too.

Right.  Here I can ignore errors, but I should still check ret2 >= 0 before
taking random bits out of it.

Paolo

> 
> > +        ret |= (ret2 & BDRV_BLOCK_ZERO);
> > +    }
> > +
> >      return ret;
> >  }
> 
> Kevin
>