iotests/244: Test preallocation for data-file-raw

Three test cases:
(1) Adding a qcow2 (metadata) file to an existing data file, see whether
    we can read the existing data through the qcow2 image.
(2) Append data to the data file, grow the qcow2 image accordingly, see
    whether we can read the new data through the qcow2 image.
(3) At runtime, add a backing image to a freshly created qcow2 image
    with an external data file (with data-file-raw).  Reading data from
    the qcow2 image must return the same result as reading data from the
    data file, so everything in the backing image must be ignored.
    (This did not use to be the case, because without the L2 tables
    preallocated, all clusters would appear as unallocated, and so the
    qcow2 driver would fall through to the backing file.)

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20210326145509.163455-3-mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 104 insertions, 0 deletions

diff --git a/tests/qemu-iotests/244 b/tests/qemu-iotests/244
index a46b441627..3e61fa25bb 100755
--- a/tests/qemu-iotests/244
+++ b/tests/qemu-iotests/244
@@ -38,6 +38,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 # get standard environment, filters and checks
 . ./common.rc
 . ./common.filter
+. ./common.qemu
 
 _supported_fmt qcow2
 _supported_proto file
@@ -267,6 +268,109 @@ case $result in
         ;;
 esac
 
+echo
+echo '=== Preallocation with data-file-raw ==='
+
+echo
+echo '--- Using a non-zeroed data file ---'
+
+# Using data-file-raw must enforce at least metadata preallocation so
+# that it does not matter whether one reads the raw file or the qcow2
+# file
+
+# Pre-create the data file, write some data.  Real-world use cases for
+# this are adding a qcow2 metadata file to a block device (i.e., using
+# the device as the data file) or adding qcow2 features to pre-existing
+# raw images (e.g. because the user now wants persistent dirty bitmaps).
+truncate -s 1M "$TEST_IMG.data"
+$QEMU_IO -f raw -c 'write -P 42 0 1M' "$TEST_IMG.data" | _filter_qemu_io
+
+# We cannot use qemu-img to create the qcow2 image, because it would
+# clear the data file.  Use the blockdev-create job instead, which will
+# only format the qcow2 image file.
+touch "$TEST_IMG"
+_launch_qemu \
+    -blockdev file,node-name=data,filename="$TEST_IMG.data" \
+    -blockdev file,node-name=meta,filename="$TEST_IMG"
+
+_send_qemu_cmd $QEMU_HANDLE '{ "execute": "qmp_capabilities" }' 'return'
+
+_send_qemu_cmd $QEMU_HANDLE \
+    '{ "execute": "blockdev-create",
+       "arguments": {
+           "job-id": "create",
+           "options": {
+               "driver": "qcow2",
+               "size": '"$((1 * 1024 * 1024))"',
+               "file": "meta",
+               "data-file": "data",
+               "data-file-raw": true
+           } } }' \
+    '"status": "concluded"'
+
+_send_qemu_cmd $QEMU_HANDLE \
+    '{ "execute": "job-dismiss", "arguments": { "id": "create" } }' \
+    'return'
+
+_cleanup_qemu
+
+echo
+echo 'Comparing pattern:'
+
+# Reading from either the qcow2 file or the data file should return
+# the same result:
+$QEMU_IO -f raw -c 'read -P 42 0 1M' "$TEST_IMG.data" | _filter_qemu_io
+$QEMU_IO -f $IMGFMT -c 'read -P 42 0 1M' "$TEST_IMG" | _filter_qemu_io
+
+# For good measure
+$QEMU_IMG compare -f raw "$TEST_IMG.data" "$TEST_IMG"
+
+echo
+echo '--- Truncation (growing) ---'
+
+# Append some new data to the raw file, then resize the qcow2 image
+# accordingly and see whether the new data is visible.  Technically
+# that is not allowed, but it is reasonable behavior, so test it.
+truncate -s 2M "$TEST_IMG.data"
+$QEMU_IO -f raw -c 'write -P 84 1M 1M' "$TEST_IMG.data" | _filter_qemu_io
+
+$QEMU_IMG resize "$TEST_IMG" 2M
+
+echo
+echo 'Comparing pattern:'
+
+$QEMU_IO -f raw -c 'read -P 42 0 1M' -c 'read -P 84 1M 1M' "$TEST_IMG.data" \
+    | _filter_qemu_io
+$QEMU_IO -f $IMGFMT -c 'read -P 42 0 1M' -c 'read -P 84 1M 1M' "$TEST_IMG" \
+    | _filter_qemu_io
+
+$QEMU_IMG compare -f raw "$TEST_IMG.data" "$TEST_IMG"
+
+echo
+echo '--- Giving a backing file at runtime ---'
+
+# qcow2 files with data-file-raw cannot have backing files given by
+# their image header, but qemu will allow you to set a backing node at
+# runtime -- it should not have any effect, though (because reading
+# from the qcow2 node should return the same data as reading from the
+# raw node).
+
+_make_test_img -o "data_file=$TEST_IMG.data,data_file_raw=on" 1M
+TEST_IMG="$TEST_IMG.base" _make_test_img 1M
+
+# Write something that is not zero into the base image
+$QEMU_IO -c 'write -P 42 0 1M' "$TEST_IMG.base" | _filter_qemu_io
+
+echo
+echo 'Comparing qcow2 image and raw data file:'
+
+# $TEST_IMG and $TEST_IMG.data must show the same data at all times;
+# that is, the qcow2 node must not fall through to the backing image
+# at any point
+$QEMU_IMG compare --image-opts \
+    "driver=raw,file.filename=$TEST_IMG.data"  \
+    "file.filename=$TEST_IMG,backing.file.filename=$TEST_IMG.base"
+
 # success, all done
 echo "*** done"
 rm -f $seq.full