On 04.05.2017 05:07, Eric Blake wrote: > We were throwing away the preallocation information associated with > zero clusters. But we should be matching the well-defined semantics > in bdrv_get_block_status(), where (BDRV_BLOCK_ZERO | > BDRV_BLOCK_OFFSET_VALID) informs the user which offset is reserved, > while still reminding the user that reading from that offset is > likely to read garbage. > > count_contiguous_clusters_by_type() is now used only for unallocated > cluster runs, hence it gets renamed and tightened. > > Making this change lets us see which portions of an image are zero > but preallocated, when using qemu-img map --output=json. The > --output=human side intentionally ignores all zero clusters, whether > or not they are preallocated. > > The fact that there is no change to qemu-iotests './check -qcow2' > merely means that we aren't yet testing this aspect of qemu-img; > a later patch will add a test. > > Signed-off-by: Eric Blake <ebl...@redhat.com> > > --- > v12: rename helper function > v11: reserved for blkdebug half of v10 > v10: new patch > --- > block/qcow2-cluster.c | 45 +++++++++++++++++++++++++++++++++++---------- > 1 file changed, 35 insertions(+), 10 deletions(-)
Reviewed-by: Max Reitz <mre...@redhat.com>
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