Re: [PATCH 3/4] block: Add blk_make_empty()

[Eric Blake]

On 4/28/20 8:55 AM, Eric Blake wrote:

> > +++ b/include/sysemu/block-backend.h
> > @@ -266,4 +266,6 @@ int coroutine_fn blk_co_copy_range(BlockBackend 
> > *blk_in, int64_t off_in,
> >   const BdrvChild *blk_root(BlockBackend *blk);
> > +int blk_make_empty(BlockBackend *blk, Error **errp);
> > +
>
> Again, a flag parameter to allow use of BDRV_REQ_NO_FALLBACK would be nice.

Or maybe not, after reading Kevin's responses.  Making an image empty is 
not the same as making it read as zero.  If we can't come up with a use 
for a flag, then deferring the addition of a flag until later is a 
perfectly reasonable approach (rather than adding a flag now that will 
never get set to anything other than 0).  This isn't quite the same as a 
public API where we would regret being locked out of a flag down the road.


--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org