[Libguestfs] [nbdkit PATCH 2/3] vddk: Do not report hole extents to be zero with single-link=true

the data in holes is actually not zeros as there might be a parent image having other data. Properly reporting (non-)zero hole extents allows clients to have information about whether the data in the image is unallocated, but the read will return zero blocks (HOLE+ZERO) or whether the data is just not in this later of the image (only HOLE). Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com&gt; --- plugins/vddk/vddk.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/plugins/vddk/vddk.c b/plugins/vddk/vddk.c index 8cf54f6e2b96..cda670325b85 100644 --- a/plugins/vddk/vddk.c +++ b/plugins/vddk/vddk.c @@ -773,9 +773,17 @@ static int add_extent (struct nbdkit_extents *extents, uint64_t *position, uint64_t next_position, bool is_hole) { - const uint32_t type = is_hole ? NBDKIT_EXTENT_HOLE|NBDKIT_EXTENT_ZERO : 0; + uint32_t type = 0; const uint64_t length = next_position - *position; + if (is_hole) { + type = NBDKIT_EXTENT_HOLE; + /* Images opened as single link might be backed by another file in the + chain, so the holes are not guaranteed to be zeros. */ + if (!single_link) + type |= NBDKIT_EXTENT_ZERO; + } + assert (*position <= next_position); if (*position == next_position) return 0; -- 2.21.0