qemu-img: Make unallocated part of backing chain obvious in map

The recently-added NBD context qemu:allocation-depth is able to
distinguish between locally-present data (even when that data is
sparse) [shown as depth 1 over NBD], and data that could not be found
anywhere in the backing chain [shown as depth 0]; and the libnbd
project was recently patched to give the human-readable name "absent"
to an allocation-depth of 0.  But qemu-img map --output=json predates
that addition, and has the unfortunate behavior that all portions of
the backing chain that resolve without finding a hit in any backing
layer report the same depth as the final backing layer.  This makes it
harder to reconstruct a qcow2 backing chain using just 'qemu-img map'
output, especially when using "backing":null to artificially limit a
backing chain, because it is impossible to distinguish between a
QCOW2_CLUSTER_UNALLOCATED (which defers to a [missing] backing file)
and a QCOW2_CLUSTER_ZERO_PLAIN cluster (which would override any
backing file), since both types of clusters otherwise show as
"data":false,"zero":true" (but note that we can distinguish a
QCOW2_CLUSTER_ZERO_ALLOCATED, which would also have an "offset":
listing).

The task of reconstructing a qcow2 chain was made harder in commit
0da9856851 (nbd: server: Report holes for raw images), because prior
to that point, it was possible to abuse NBD's block status command to
see which portions of a qcow2 file resulted in BDRV_BLOCK_ALLOCATED
(showing up as NBD_STATE_ZERO in isolation) vs. missing from the chain
(showing up as NBD_STATE_ZERO|NBD_STATE_HOLE); but now qemu reports
more accurate sparseness information over NBD.

An obvious solution is to make 'qemu-img map --output=json' add an
additional "present":false designation to any cluster lacking an
allocation anywhere in the chain, without any change to the "depth"
parameter to avoid breaking existing clients.  The iotests have
several examples where this distinction demonstrates the additional
accuracy.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210701190655.2131223-3-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: fix more iotest fallout]
Signed-off-by: Eric Blake <eblake@redhat.com>

1 files changed, 97 insertions, 93 deletions

diff --git a/tests/qemu-iotests/154.out b/tests/qemu-iotests/154.out
index 4863e24838..1fa7ffc475 100644
--- a/tests/qemu-iotests/154.out
+++ b/tests/qemu-iotests/154.out
@@ -11,14 +11,14 @@ wrote 2048/2048 bytes at offset 17408
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 2048/2048 bytes at offset 27648
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 4096, "length": 4096, "depth": 1, "zero": true, "data": false},
-{ "start": 8192, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 12288, "length": 4096, "depth": 1, "zero": true, "data": false},
-{ "start": 16384, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 20480, "length": 4096, "depth": 1, "zero": true, "data": false},
-{ "start": 24576, "length": 8192, "depth": 0, "zero": true, "data": false},
-{ "start": 32768, "length": 134184960, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 4096, "length": 4096, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 8192, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 12288, "length": 4096, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 16384, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 20480, "length": 4096, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 24576, "length": 8192, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 32768, "length": 134184960, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == backing file contains non-zero data before write_zeroes ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -41,11 +41,11 @@ read 1024/1024 bytes at offset 65536
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 2048/2048 bytes at offset 67584
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 32768, "depth": 1, "zero": true, "data": false},
-{ "start": 32768, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 36864, "length": 28672, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 69632, "length": 134148096, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 32768, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 32768, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 36864, "length": 28672, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 65536, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 69632, "length": 134148096, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == backing file contains non-zero data after write_zeroes ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -68,11 +68,11 @@ read 1024/1024 bytes at offset 44032
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 3072/3072 bytes at offset 40960
 3 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 32768, "depth": 1, "zero": true, "data": false},
-{ "start": 32768, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 36864, "length": 4096, "depth": 1, "zero": true, "data": false},
-{ "start": 40960, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 45056, "length": 134172672, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 32768, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 32768, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 36864, "length": 4096, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 40960, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 45056, "length": 134172672, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == write_zeroes covers non-zero data ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -101,15 +101,15 @@ wrote 2048/2048 bytes at offset 29696
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 4096/4096 bytes at offset 28672
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 4096, "depth": 1, "zero": true, "data": false},
-{ "start": 4096, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 8192, "length": 4096, "depth": 1, "zero": true, "data": false},
-{ "start": 12288, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 16384, "length": 4096, "depth": 1, "zero": true, "data": false},
-{ "start": 20480, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 24576, "length": 4096, "depth": 1, "zero": true, "data": false},
-{ "start": 28672, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 32768, "length": 134184960, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 4096, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 4096, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 8192, "length": 4096, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 12288, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 16384, "length": 4096, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 20480, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 24576, "length": 4096, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 28672, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 32768, "length": 134184960, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == spanning two clusters, non-zero before request ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -142,16 +142,16 @@ read 1024/1024 bytes at offset 67584
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 5120/5120 bytes at offset 68608
 5 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 32768, "depth": 1, "zero": true, "data": false},
-{ "start": 32768, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 36864, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 40960, "length": 8192, "depth": 1, "zero": true, "data": false},
-{ "start": 49152, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 53248, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 57344, "length": 8192, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 69632, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 73728, "length": 134144000, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 32768, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 32768, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 36864, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 40960, "length": 8192, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 49152, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 53248, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 57344, "length": 8192, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 65536, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 69632, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 73728, "length": 134144000, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == spanning two clusters, non-zero after request ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -184,16 +184,16 @@ read 7168/7168 bytes at offset 65536
 7 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 1024/1024 bytes at offset 72704
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 32768, "depth": 1, "zero": true, "data": false},
-{ "start": 32768, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 36864, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 40960, "length": 8192, "depth": 1, "zero": true, "data": false},
-{ "start": 49152, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 53248, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 57344, "length": 8192, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 69632, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 73728, "length": 134144000, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 32768, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 32768, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 36864, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 40960, "length": 8192, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 49152, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 53248, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 57344, "length": 8192, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 65536, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 69632, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 73728, "length": 134144000, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == spanning two clusters, partially overwriting backing file ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -212,8 +212,8 @@ read 1024/1024 bytes at offset 5120
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 2048/2048 bytes at offset 6144
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 8192, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 8192, "length": 134209536, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 8192, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 8192, "length": 134209536, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == spanning multiple clusters, non-zero in first cluster ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -226,10 +226,10 @@ read 2048/2048 bytes at offset 65536
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 10240/10240 bytes at offset 67584
 10 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 65536, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 69632, "length": 8192, "depth": 0, "zero": true, "data": false},
-{ "start": 77824, "length": 134139904, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 65536, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 65536, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 69632, "length": 8192, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 77824, "length": 134139904, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == spanning multiple clusters, non-zero in intermediate cluster ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -240,9 +240,9 @@ wrote 7168/7168 bytes at offset 67584
 7 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 12288/12288 bytes at offset 65536
 12 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 65536, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 12288, "depth": 0, "zero": true, "data": false},
-{ "start": 77824, "length": 134139904, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 65536, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 65536, "length": 12288, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 77824, "length": 134139904, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == spanning multiple clusters, non-zero in final cluster ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -255,10 +255,10 @@ read 10240/10240 bytes at offset 65536
 10 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 2048/2048 bytes at offset 75776
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 65536, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 8192, "depth": 0, "zero": true, "data": false},
-{ "start": 73728, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 77824, "length": 134139904, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 65536, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 65536, "length": 8192, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 73728, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 77824, "length": 134139904, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == spanning multiple clusters, partially overwriting backing file ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
@@ -277,84 +277,88 @@ read 2048/2048 bytes at offset 74752
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 1024/1024 bytes at offset 76800
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 65536, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 69632, "length": 4096, "depth": 0, "zero": true, "data": false},
-{ "start": 73728, "length": 4096, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
-{ "start": 77824, "length": 134139904, "depth": 1, "zero": true, "data": false}]
+[{ "start": 0, "length": 65536, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 65536, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 69632, "length": 4096, "depth": 0, "present": true, "zero": true, "data": false},
+{ "start": 73728, "length": 4096, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET},
+{ "start": 77824, "length": 134139904, "depth": 1, "present": false, "zero": true, "data": false}]
 
 == unaligned image tail cluster, no allocation needed ==
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776
 wrote 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134219776, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 0, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776
 wrote 512/512 bytes at offset 134219264
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134219776, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 0, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776
 wrote 1024/1024 bytes at offset 134218240
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134219776, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 0, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776
 wrote 2048/2048 bytes at offset 134217728
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134219776, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 0, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134218752
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134219264
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 134218240
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2048/2048 bytes at offset 134217728
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 wrote 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134219264
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 134218240
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2048/2048 bytes at offset 134217728
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134218752
 wrote 1024/1024 bytes at offset 134217728
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
@@ -365,15 +369,15 @@ read 512/512 bytes at offset 134217728
 read 512/512 bytes at offset 134218240
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 1024/1024 bytes allocated at offset 128 MiB
-[{ "start": 0, "length": 134217728, "depth": 0, "zero": true, "data": false},
-{ "start": 134217728, "length": 1024, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
+[{ "start": 0, "length": 134217728, "depth": 0, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 1024, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET}]
 wrote 1024/1024 bytes at offset 134217728
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 1024/1024 bytes allocated at offset 128 MiB
 read 1024/1024 bytes at offset 134217728
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 134217728, "depth": 0, "zero": true, "data": false},
-{ "start": 134217728, "length": 1024, "depth": 0, "zero": true, "data": false, "offset": OFFSET}]
+[{ "start": 0, "length": 134217728, "depth": 0, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 1024, "depth": 0, "present": true, "zero": true, "data": false, "offset": OFFSET}]
 
 == unaligned image tail cluster, allocation required ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134218752
@@ -386,8 +390,8 @@ read 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 1536/1536 bytes at offset 134218240
 1.500 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET}]
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134218752
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134218240
@@ -408,6 +412,6 @@ read 512/512 bytes at offset 134218240
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 1024/1024 bytes at offset 134218752
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
-{ "start": 134217728, "length": 2048, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
+[{ "start": 0, "length": 134217728, "depth": 1, "present": false, "zero": true, "data": false},
+{ "start": 134217728, "length": 2048, "depth": 0, "present": true, "zero": false, "data": true, "offset": OFFSET}]
 *** done