Re: [Qemu-devel] [PATCH 5/6] qcow2: Let vmstate call qcow2_co_preadv/pwrite directly

[Fam Zheng <famz@redhat.com>]

On Fri, 06/10 16:39, Eric Blake wrote:
> > +++ b/block/qcow2.c
> > @@ -2903,36 +2903,20 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
> >                                int64_t pos)
> >  {
> >      BDRVQcow2State *s = bs->opaque;
> > -    int64_t total_sectors = bs->total_sectors;
> > -    bool zero_beyond_eof = bs->zero_beyond_eof;
> > -    int ret;
> >  
> >      BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
> > -    bs->zero_beyond_eof = false;
> > -    ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov);
> > -    bs->zero_beyond_eof = zero_beyond_eof;
> > -
> > -    /* bdrv_co_do_writev will have increased the total_sectors value to include
> > -     * the VM state - the VM state is however not an actual part of the block
> > -     * device, therefore, we need to restore the old value. */
> > -    bs->total_sectors = total_sectors;
> > -
> > -    return ret;
> > +    return bs->drv->bdrv_co_pwritev(bs, qcow2_vm_state_offset(s) + pos,
> > +                                    qiov->size, qiov, 0);
> >  }
> 
> bs->drv->bdrv_co_pwritev() is an optional interface; not all the drivers
> have it yet.  Should you be asserting that it exists, and/or returning
> an error if it does not?

bs->drv is always qcow2 driver here so this is correct.

> 
> >  
> >  static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
> >                                int64_t pos)
> >  {
> >      BDRVQcow2State *s = bs->opaque;
> > -    bool zero_beyond_eof = bs->zero_beyond_eof;
> > -    int ret;
> >  
> >      BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD);
> > -    bs->zero_beyond_eof = false;
> > -    ret = bdrv_preadv(bs, qcow2_vm_state_offset(s) + pos, qiov);
> > -    bs->zero_beyond_eof = zero_beyond_eof;
> > -
> > -    return ret;
> > +    return bs->drv->bdrv_co_preadv(bs, qcow2_vm_state_offset(s) + pos,
> > +                                   qiov->size, qiov, 0);
> 
> Ditto.
> 

Fam