Re: [Qemu-devel] [PATCH 2/4] block: immediately cancel oversized read/write requests

[Peter Lieven]

On 08.09.2014 15:49, Paolo Bonzini wrote:
> Il 08/09/2014 15:44, Benoît Canet ha scritto:
> > > > +    if (bs->bl.max_transfer_length && nb_sectors > bs->bl.max_transfer_length) 
> > > > {
> > > > +        error_report("read of %d sectors at sector %ld exceeds device max"
> > > > +                     " transfer length of %d sectors.", nb_sectors, sector_num,
> > > > +                     bs->bl.max_transfer_length);
> > > > +        return -EINVAL;
> > > > +    }
> > > > +
> > > >       return bdrv_co_do_preadv(bs, sector_num << BDRV_SECTOR_BITS,
> > > >                                nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
> > > >   }
> > > > @@ -3507,6 +3514,13 @@ static int coroutine_fn 
> > > > bdrv_co_do_writev(BlockDriverState *bs,
> > > >           return -EINVAL;
> > > >       }
> > > >   
> > > > +    if (bs->bl.max_transfer_length && nb_sectors > bs->bl.max_transfer_length) {
> > > > +        error_report("write of %d sectors at sector %ld exceeds device max"
> > > > +                     " transfer length of %d sectors.", nb_sectors, sector_num,
> > > > +                     bs->bl.max_transfer_length);
> > > > +        return -EINVAL;
> > > > +    }
> > > > +
> > > >       return bdrv_co_do_pwritev(bs, sector_num << BDRV_SECTOR_BITS,
> > > >                                 nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
> > > >   }
> > > > --
> > > > 1.7.9.5
> > Look like you are changing the coroutine version.
> >
> > Some hardware like virtio-blk uses the AIO version of read and writes.
> > What would happen if all the block drivers down the chain are AIO enabled ?
> The AIO version still goes through bdrv_co_do_readv/writev.
>
> However, error_report is not something you can use for guest-accessible
> error messages, unless you want your logs to fill up with error messages. :)

So you would not throw an error msg here?

Peter