iotests: Add test 179 to cover write zeroes with unmap

No tests were covering write zeroes with unmap.  Additionally,
I needed to prove that my previous patches for correct status
reporting and write zeroes optimizations actually had an impact.

The test works for cluster_size between 8k and 2M (for smaller
sizes, it fails because our allocation patterns are not contiguous
with small clusters - in part, the largest consecutive allocation
we tend to get is often bounded by the size covered by one L2
table).

Note that testing for zero clusters is tricky: 'qemu-io map'
reports whether data comes from the current layer of the image
(useful for sniffing out which regions of the file have
QCOW_OFLAG_ZERO) - but doesn't show which clusters have mappings;
while 'qemu-img map' sees "zero":true for both unallocated and
zero clusters for any qcow2 with no backing layer (so less useful
at detecting true zero clusters), but reliably shows mappings.
So we have to rely on both queries side-by-side at each point of
the test.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170507000552.20847-10-eblake@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 130 insertions, 0 deletions

diff --git a/tests/qemu-iotests/179 b/tests/qemu-iotests/179
new file mode 100755
index 0000000..7bc8db8
--- /dev/null
+++ b/tests/qemu-iotests/179
@@ -0,0 +1,130 @@
+#!/bin/bash
+#
+# Test case for write zeroes with unmap
+#
+# Copyright (C) 2017 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/>.
+#
+
+# creator
+owner=eblake@redhat.com
+
+seq="$(basename $0)"
+echo "QA output created by $seq"
+
+here="$PWD"
+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
+
+# v2 images can't mark clusters as zero
+_unsupported_imgopts compat=0.10
+
+echo
+echo '=== Testing write zeroes with unmap ==='
+echo
+
+TEST_IMG="$TEST_IMG.base" _make_test_img 64M
+_make_test_img -b "$TEST_IMG.base"
+
+# Offsets chosen at or near 2M boundaries so test works at all cluster sizes
+# 8k and larger (smaller clusters fail due to non-contiguous allocations)
+
+# Aligned writes to unallocated cluster should not allocate mapping, but must
+# mark cluster as zero, whether or not unmap was requested
+$QEMU_IO -c "write -z -u 2M 2M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write -z 6M 2M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "map" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IMG map --output=json "$TEST_IMG.base" | _filter_qemu_img_map
+
+# Unaligned writes need not allocate mapping if the cluster already reads
+# as zero, but must mark cluster as zero, whether or not unmap was requested
+$QEMU_IO -c "write -z -u 10485761 2097150" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write -z 14680065 2097150" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "map" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IMG map --output=json "$TEST_IMG.base" | _filter_qemu_img_map
+
+# Requesting unmap of normal data must deallocate; omitting unmap should
+# preserve the mapping
+$QEMU_IO -c "write 18M 14M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write -z -u 20M 2M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write -z 24M 6M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "map" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IMG map --output=json "$TEST_IMG.base" | _filter_qemu_img_map
+
+# Likewise when writing on already-mapped zero data
+$QEMU_IO -c "write -z -u 26M 2M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write -z 28M 2M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "map" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IMG map --output=json "$TEST_IMG.base" | _filter_qemu_img_map
+
+# Writing on unmapped zeroes does not allocate
+$QEMU_IO -c "write -z 32M 8M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write -z -u 34M 2M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write -z 36M 2M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "map" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IMG map --output=json "$TEST_IMG.base" | _filter_qemu_img_map
+
+# Writing zero overrides a backing file, regardless of backing cluster type
+$QEMU_IO -c "write -z 40M 8M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write 48M 8M" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "write -z -u 42M 2M" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write -z 44M 2M" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write -z -u 50M 2M" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write -z 52M 2M" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write -z -u 58M 2M" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "write -z 60M 2M" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "map" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
+
+# Final check that mappings are correct and images are still sane
+TEST_IMG="$TEST_IMG.base" _check_test_img
+_check_test_img
+
+echo
+echo '=== Testing cache optimization ==='
+echo
+
+BLKDBG_TEST_IMG="blkdebug:$TEST_DIR/blkdebug.conf:$TEST_IMG.base"
+
+cat > "$TEST_DIR/blkdebug.conf" <<EOF
+[inject-error]
+event = "l2_update"
+errno = "5"
+immediately = "on"
+once = "off"
+EOF
+
+# None of the following writes should trigger an L2 update, because the
+# cluster already reads as zero, and we don't have to change allocation
+$QEMU_IO -c "w -z -u 20M 2M" "$BLKDBG_TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "w -z 20M 2M" "$BLKDBG_TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "w -z 28M 2M" "$BLKDBG_TEST_IMG" | _filter_qemu_io
+
+# success, all done
+echo '*** done'
+status=0