iotests: test big qcow2 shrink

This test checks bug in qcow2_process_discards, fixed by previous
commit.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/250

@@ -0,0 +1,78 @@
+#!/usr/bin/env bash
+#
+# Test big discard in qcow2 shrink
+#
+# Copyright (c) 2019 Virtuozzo International GmbH. All rights reserved.
+#
+# 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/>.
+#
+
+# creator
+owner=vsementsov@virtuozzo.com
+
+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
+
+_supported_fmt qcow2
+_supported_proto file
+_supported_os Linux
+
+# This test checks that qcow2_process_discards does not truncate a discard
+# request > 2G.
+# To reproduce bug we need to overflow int by one sequential discard, so we
+# need size > 2G, bigger cluster size (as with default 64k we may have maximum
+# of 512M sequential data, corresponding to one L1 entry), and we need some
+# data of the beginning of the disk mapped to the end of file to prevent
+# bdrv_co_truncate(bs->file) call in qcow2_co_truncate(), which might succeed
+# anyway.
+
+disk_usage()
+{
+    du --block-size=1 $1 | awk '{print $1}'
+}
+
+size=2100M
+IMGOPTS="cluster_size=1M,preallocation=metadata"
+
+_make_test_img $size
+$QEMU_IO -c 'discard 0 10M' -c 'discard 2090M 10M' \
+         -c 'write 2090M 10M' -c 'write 0 10M' "$TEST_IMG" | _filter_qemu_io
+
+# Check that our trick with swapping first and last 10M chunks succeeded.
+# Otherwise test may pass even if bdrv_pdiscard() fails in
+# qcow2_process_discards()
+$QEMU_IMG map "$TEST_IMG" | _filter_testdir
+
+before=$(disk_usage "$TEST_IMG")
+$QEMU_IMG resize --shrink "$TEST_IMG" 5M
+after=$(disk_usage "$TEST_IMG")
+
+echo "Disk usage delta: $((before - after))"
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0

tests/qemu-iotests/250.out

@@ -0,0 +1,16 @@
+QA output created by 250
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202009600 preallocation=metadata
+discard 10485760/10485760 bytes at offset 0
+10 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 10485760/10485760 bytes at offset 2191523840
+10 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 10485760/10485760 bytes at offset 2191523840
+10 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 10485760/10485760 bytes at offset 0
+10 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+Offset          Length          Mapped to       File
+0               0xa00000        0x82f00000      TEST_DIR/t.qcow2
+0x82a00000      0xa00000        0x500000        TEST_DIR/t.qcow2
+Image resized.
+Disk usage delta: 15728640
+*** done

tests/qemu-iotests/group

@@ -262,6 +262,7 @@
 247 rw quick
 248 rw quick
 249 rw auto quick
+250 rw auto quick
 252 rw auto backing quick
 253 rw auto quick
 254 rw auto backing quick