On 05/03/2017 06:11 PM, Max Reitz wrote: > In discard_single_l2(), we completely discard normal clusters instead of > simply turning them into preallocated zero clusters. That means we > should probably do the same with such preallocated zero clusters: > Discard them instead of keeping them allocated. > > Reported-by: Eric Blake <ebl...@redhat.com> > Signed-off-by: Max Reitz <mre...@redhat.com> > --- > block/qcow2-cluster.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-)
Reviewed-by: Eric Blake <ebl...@redhat.com>
>
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index fb91fd8979..31077d8102 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -1511,7 +1511,8 @@ static int discard_single_l2(BlockDriverState *bs,
> uint64_t offset,
> break;
>
> case QCOW2_CLUSTER_ZERO:
> - if (!full_discard) {
> + /* Preallocated zero clusters should be discarded in any
> case */
> + if (!full_discard && (old_l2_entry & L2E_OFFSET_MASK) == 0) {
Again, if we had a separate QCOW2_CLUSTER_* for plain vs. pre-allocated
zero, this might be easier to write.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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