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A discard request deallocates the selected clusters so they read back as zeroes. This is done by clearing the cluster offset field and setting QCOW_OFLAG_ZERO in the L2 entry. This flag is however only supported when qcow_version >= 3. In older images the cluster is simply deallocated, exposing any possible stale data from the backing file. Since discard is an advisory operation it's safer to simply forbid it in this scenario. Note that we are adding this check to qcow2_co_pdiscard() and not to qcow2_cluster_discard() or discard_in_l2_slice() because the last two are also used by qcow2_snapshot_create() to discard the clusters used by the VM state. In this case there's no risk of exposing stale data to the guest and we really want that the clusters are always discarded. Signed-off-by: Alberto Garcia <berto@igalia.com> Message-Id: <20200331114345.29993-1-berto@igalia.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
98 lines
3.1 KiB
Bash
Executable File
98 lines
3.1 KiB
Bash
Executable File
#!/usr/bin/env bash
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#
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# Test how 'qemu-io -c discard' behaves on v2 and v3 qcow2 images
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#
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# Copyright (C) 2020 Igalia, S.L.
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# Author: Alberto Garcia <berto@igalia.com>
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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# creator
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owner=berto@igalia.com
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seq=`basename $0`
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echo "QA output created by $seq"
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status=1 # failure is the default!
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_cleanup()
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{
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_cleanup_test_img
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}
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trap "_cleanup; exit \$status" 0 1 2 3 15
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# get standard environment, filters and checks
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. ./common.rc
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. ./common.filter
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_supported_fmt qcow2
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_supported_proto file
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_supported_os Linux
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_unsupported_imgopts 'compat=0.10' refcount_bits data_file
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echo
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echo "### Test 'qemu-io -c discard' on a QCOW2 image without a backing file"
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echo
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for qcow2_compat in 0.10 1.1; do
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echo "# Create an image with compat=$qcow2_compat without a backing file"
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_make_test_img -o "compat=$qcow2_compat" 128k
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echo "# Fill all clusters with data and then discard them"
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$QEMU_IO -c 'write -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
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$QEMU_IO -c 'discard 0 128k' "$TEST_IMG" | _filter_qemu_io
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echo "# Read the data from the discarded clusters"
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$QEMU_IO -c 'read -P 0x00 0 128k' "$TEST_IMG" | _filter_qemu_io
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echo "# Output of qemu-img map"
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$QEMU_IMG map "$TEST_IMG" | _filter_testdir
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done
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echo
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echo "### Test 'qemu-io -c discard' on a QCOW2 image with a backing file"
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echo
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echo "# Create a backing image and fill it with data"
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BACKING_IMG="$TEST_IMG.base"
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TEST_IMG="$BACKING_IMG" _make_test_img 128k
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$QEMU_IO -c 'write -P 0xff 0 128k' "$BACKING_IMG" | _filter_qemu_io
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for qcow2_compat in 0.10 1.1; do
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echo "# Create an image with compat=$qcow2_compat and a backing file"
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_make_test_img -o "compat=$qcow2_compat" -b "$BACKING_IMG"
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echo "# Fill all clusters with data and then discard them"
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$QEMU_IO -c 'write -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
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$QEMU_IO -c 'discard 0 128k' "$TEST_IMG" | _filter_qemu_io
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echo "# Read the data from the discarded clusters"
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if [ "$qcow2_compat" = "1.1" ]; then
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# In qcow2 v3 clusters are zeroed (with QCOW_OFLAG_ZERO)
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$QEMU_IO -c 'read -P 0x00 0 128k' "$TEST_IMG" | _filter_qemu_io
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else
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# In qcow2 v2 if there's a backing image we cannot zero the clusters
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# without exposing the backing file data so discard does nothing
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$QEMU_IO -c 'read -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
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fi
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echo "# Output of qemu-img map"
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$QEMU_IMG map "$TEST_IMG" | _filter_testdir
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done
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# success, all done
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echo "*** done"
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rm -f $seq.full
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status=0
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