iotests: Add test for 4G+ compressed qcow2 write

Test what qemu-img check says about an image after one has written
compressed data to an offset above 4 GB.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20191028161841.1198-3-mreitz@redhat.com
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

tests/qemu-iotests/272

@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+#
+# Test compressed write to a qcow2 image at an offset above 4 GB
+#
+# Copyright (C) 2019 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+seq=$(basename "$0")
+echo "QA output created by $seq"
+
+status=1	# failure is the default!
+
+_cleanup()
+{
+    _cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+# This is a qcow2 regression test
+_supported_fmt qcow2
+_supported_proto file
+
+# External data files do not support compression;
+# We need an exact cluster size (2M) and refcount width (2) so we can
+# get this test quickly over with; and this in turn require
+# compat=1.1
+_unsupported_imgopts data_file cluster_size refcount_bits 'compat=0.10'
+
+# The idea is: Create an empty file, mark the first 4 GB as used, then
+# do a compressed write that thus must be put beyond 4 GB.
+# (This used to fail because the compressed sector mask was just a
+# 32 bit mask, so qemu-img check will count a cluster before 4 GB as
+# referenced twice.)
+
+# We would like to use refcount_bits=1 here, but then qemu-img check
+# will throw an error when trying to count a cluster as referenced
+# twice.
+_make_test_img -o cluster_size=2M,refcount_bits=2 64M
+
+reft_offs=$(peek_file_be "$TEST_IMG" 48 8)
+refb_offs=$(peek_file_be "$TEST_IMG" $reft_offs 8)
+
+# We want to cover 4 GB, those are 2048 clusters, equivalent to
+# 4096 bit = 512 B.
+truncate -s 4G "$TEST_IMG"
+for ((in_refb_offs = 0; in_refb_offs < 512; in_refb_offs += 8)); do
+    poke_file "$TEST_IMG" $((refb_offs + in_refb_offs)) \
+        '\x55\x55\x55\x55\x55\x55\x55\x55'
+done
+
+$QEMU_IO -c 'write -c -P 42 0 2M' "$TEST_IMG" | _filter_qemu_io
+
+echo
+echo '--- Check ---'
+
+# This should only print the leaked clusters in the first 4 GB
+_check_test_img | grep -v '^Leaked cluster '
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0

tests/qemu-iotests/272.out

@@ -0,0 +1,10 @@
+QA output created by 272
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+wrote 2097152/2097152 bytes at offset 0
+2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+--- Check ---
+
+2044 leaked clusters were found on the image.
+This means waste of disk space, but no harm to data.
+*** done

tests/qemu-iotests/group

@@ -283,3 +283,4 @@
 267 rw auto quick snapshot
 268 rw auto quick
 270 rw backing quick
+272 rw