[PATCH v4 2/3] iotests: add qcow2-discard-during-rewrite

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Simple test:
 - start writing to allocated cluster A
 - discard this cluster
 - write to another unallocated cluster B (it's allocated in same place
   where A was allocated)
 - continue writing to A

For now last action pollutes cluster B which is a bug fixed by the
following commit.

For now, add test to "disabled" group, so that it doesn't run
automatically.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 .../tests/qcow2-discard-during-rewrite        | 99 +++++++++++++++++++
 .../tests/qcow2-discard-during-rewrite.out    | 17 ++++
 2 files changed, 116 insertions(+)
 create mode 100755 tests/qemu-iotests/tests/qcow2-discard-during-rewrite
 create mode 100644 tests/qemu-iotests/tests/qcow2-discard-during-rewrite.out

diff --git a/tests/qemu-iotests/tests/qcow2-discard-during-rewrite b/tests/qemu-iotests/tests/qcow2-discard-during-rewrite
new file mode 100755
index 0000000000..dd9964ef3f
--- /dev/null
+++ b/tests/qemu-iotests/tests/qcow2-discard-during-rewrite
@@ -0,0 +1,99 @@
+#!/usr/bin/env bash
+# group: quick disabled
+#
+# Test discarding (and reusing) host cluster during writing data to it.
+#
+# Copyright (c) 2021 Virtuozzo International GmbH.
+#
+# 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 fuse
+_supported_os Linux
+
+size=1M
+_make_test_img $size
+
+(
+cat <<EOF
+write -P 1 0 64K
+
+break pwritev A
+aio_write -P 2 0 64K
+wait_break A
+
+aio_discard 0 64K
+EOF
+
+# Now discard must be blocked by discard_rw_lock.
+# Prior to introducing of discard_rw_lock discard
+# will run and discard the cluster we are writing
+# to. Give it a chance to do it.
+sleep 1
+
+# Write another cluster. Data writing should be
+# blocked by discard_rw_lock (as we have pending
+# writer). Prior to introducing of the lock this
+# write will allocate same cluster that was
+# discarded and successfully write to it.
+# Give it a chance.
+cat <<EOF
+aio_write -P 3 128K 64K
+EOF
+
+# a chance for write to finish
+sleep 1
+
+cat <<EOF
+resume A
+EOF
+
+# On good scenario wait for
+# 1. finish first write
+# 2. finish discard
+# 3. finish second write
+# On bad scenario discard and second write are finished,
+# wait only for first write, which will pollute data
+# of second write
+sleep 1
+
+cat <<EOF
+read -P 0 0 64K
+read -P 3 128K 64K
+EOF
+) | $QEMU_IO blkdebug::$TEST_IMG | _filter_qemu_io
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/tests/qcow2-discard-during-rewrite.out b/tests/qemu-iotests/tests/qcow2-discard-during-rewrite.out
new file mode 100644
index 0000000000..dd54e928a6
--- /dev/null
+++ b/tests/qemu-iotests/tests/qcow2-discard-during-rewrite.out
@@ -0,0 +1,17 @@
+QA output created by qcow2-discard-during-rewrite
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576
+wrote 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+blkdebug: Suspended request 'A'
+blkdebug: Resuming request 'A'
+discarded 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 65536/65536 bytes at offset 131072
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 65536/65536 bytes at offset 0
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 65536/65536 bytes at offset 131072
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+*** done
-- 
2.29.2