On Wed, May 07, 2014 at 09:45:17AM +0800, Fam Zheng wrote:
> On Tue, 05/06 10:32, Fam Zheng wrote:
> > @@ -1110,12 +1111,20 @@ static int get_cluster_offset(BlockDriverState *bs,
> > }
> >
> > /* Avoid the L2 tables update for the images that have snapshots.
> > */
> > - *cluster_offset = bdrv_getlength(extent->file);
> > + ret = bdrv_getlength(extent->file);
> > + if (ret < 0 ||
> > + ret & ((extent->cluster_sectors << BDRV_SECTOR_BITS) - 1)) {
> > + return VMDK_ERROR;
> > + }
> > + *cluster_offset = ret;
> > if (!extent->compressed) {
> > - bdrv_truncate(
> > - extent->file,
> > - *cluster_offset + (extent->cluster_sectors << 9)
> > - );
> > + ret = bdrv_write_zeroes(extent->file,
> > + *cluster_offset >> BDRV_SECTOR_BITS,
> > + extent->cluster_sectors,
> > + 0);
>
> Hi Stefan,
>
> By considering a bdrv_write_zeroes as a pre-write, it in general doubles the
> write for the whole image, so it's not a good solution.
>
> A better way would be removing the bdrv_truncate and require the caller to do
> full cluster write (with a bounce buffer if necessary).
>
> So let's drop this patch.
Okay, thanks for investigating this.
Stefan
