iotests/131: Add parallels regression test

Test an allocating write to a parallels image that has a backing node.
Before HEAD^, doing so used to give me a failed assertion (when the
backing node contains only `42` bytes; the results varies with the value
chosen, for `0` bytes, for example, all I get is EIO).

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20220714132801.72464-3-hreitz@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

tests/qemu-iotests/131

@@ -43,7 +43,7 @@ _supported_os Linux
 
 inuse_offset=$((0x2c))
 
-size=64M
+size=$((64 * 1024 * 1024))
 CLUSTER_SIZE=64k
 IMGFMT=parallels
 _make_test_img $size
@@ -70,6 +70,39 @@ _check_test_img
 _check_test_img -r all
 { $QEMU_IO -c "read -P 0x11 64k 64k" "$TEST_IMG"; } 2>&1 | _filter_qemu_io | _filter_testdir
 
+echo "== allocate with backing =="
+# Verify that allocating clusters works fine even when there is a backing image.
+# Regression test for a bug where we would pass a buffer read from the backing
+# node as a QEMUIOVector object, which could cause anything from I/O errors over
+# assertion failures to invalid reads from memory.
+
+# Clear image
+_make_test_img $size
+# Create base image
+TEST_IMG="$TEST_IMG.base" _make_test_img $size
+
+# Write some data to the base image (which would trigger an assertion failure if
+# interpreted as a QEMUIOVector)
+$QEMU_IO -c 'write -P 42 0 64k' "$TEST_IMG.base" | _filter_qemu_io
+
+# Parallels does not seem to support storing a backing filename in the image
+# itself, so we need to build our backing chain on the command line
+imgopts="driver=$IMGFMT,file.driver=$IMGPROTO,file.filename=$TEST_IMG"
+imgopts+=",backing.driver=$IMGFMT"
+imgopts+=",backing.file.driver=$IMGPROTO,backing.file.filename=$TEST_IMG.base"
+
+# Cause allocation in the top image
+QEMU_IO_OPTIONS=$QEMU_IO_OPTIONS_NO_FMT \
+    $QEMU_IO --image-opts "$imgopts" -c 'write -P 1 0 64' | _filter_qemu_io
+
+# Verify
+QEMU_IO_OPTIONS=$QEMU_IO_OPTIONS_NO_FMT \
+    $QEMU_IO --image-opts "$imgopts" \
+    -c 'read -P 1 0 64' \
+    -c "read -P 42 64 $((64 * 1024 - 64))" \
+    -c "read -P 0 64k $((size - 64 * 1024))" \
+    | _filter_qemu_io
+
 # success, all done
 echo "*** done"
 rm -f $seq.full

tests/qemu-iotests/131.out

@@ -37,4 +37,17 @@ Double checking the fixed image now...
 No errors were found on the image.
 read 65536/65536 bytes at offset 65536
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+== allocate with backing ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
+wrote 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 64/64 bytes at offset 0
+64 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 64/64 bytes at offset 0
+64 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 65472/65472 bytes at offset 64
+63.938 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 67043328/67043328 bytes at offset 65536
+63.938 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 *** done