Re: [PATCH v7 32/32] iotests: Add tests for qcow2 images with extended L2 entries

[Eric Blake <eblake@redhat.com>]

On 5/25/20 1:08 PM, Alberto Garcia wrote:
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>   tests/qemu-iotests/271     | 705 +++++++++++++++++++++++++++++++++++++
>   tests/qemu-iotests/271.out | 603 +++++++++++++++++++++++++++++++
>   tests/qemu-iotests/group   |   1 +
>   3 files changed, 1309 insertions(+)
>   create mode 100755 tests/qemu-iotests/271
>   create mode 100644 tests/qemu-iotests/271.out
> 

> +_cleanup()
> +{
> +	_cleanup_test_img
> +        rm -f "$TEST_IMG.raw"

TAB damage.


> +
> +l2_offset=262144 # 0x40000

If desired, you could write:

l2_offset=$((0x40000))

if that is more legible.

> +
> +_verify_img()
> +{
> +    $QEMU_IMG compare "$TEST_IMG" "$TEST_IMG.raw" | grep -v 'Images are identical'
> +    $QEMU_IMG check "$TEST_IMG" | _filter_qemu_img_check | \
> +        grep -v 'No errors were found on the image'
> +}
> +
> +# Compare the bitmap of an extended L2 entry against an expected value
> +_verify_l2_bitmap()
> +{
> +    entry_no="$1"            # L2 entry number, starting from 0
> +    expected_alloc="$alloc"  # Space-separated list of allocated subcluster indexes
> +    expected_zero="$zero"    # Space-separated list of zero subcluster indexes
> +
> +    offset=$(($l2_offset + $entry_no * 16))
> +    entry=`peek_file_be "$TEST_IMG" $offset 8`

I find $() easier to read than ``.

> +    offset=$(($offset + 8))
> +    bitmap=`peek_file_be "$TEST_IMG" $offset 8`
> +
> +    expected_bitmap=0
> +    for bit in $expected_alloc; do
> +        expected_bitmap=$(($expected_bitmap | (1 << $bit)))
> +    done
> +    for bit in $expected_zero; do
> +        expected_bitmap=$(($expected_bitmap | (1 << (32 + $bit))))
> +    done
> +    expected_bitmap=`printf "%llu" $expected_bitmap`

Dead statement - expected_bitmap is already a 64-bit decimal number 
without reprinting it to itself.

> +
> +    printf "L2 entry #%d: 0x%016lx %016lx\n" "$entry_no" "$entry" "$bitmap"
> +    if [ "$bitmap" != "$expected_bitmap" ]; then
> +        printf "ERROR: expecting bitmap       0x%016lx\n" "$expected_bitmap"
> +    fi
> +}
> +
> +_test_write()
> +{
> +    cmd="$1"
> +    l2_entry_idx="$2"
> +    [ -n "$l2_entry_idx" ] || l2_entry_idx=0

Could shorten these two lines into the one-liner:

l2_entry_idx=${2:-0}

> +    raw_cmd=`echo $cmd | sed s/-c//` # Raw images don't support -c
> +    echo "$cmd"
> +    $QEMU_IO -c "$cmd" "$TEST_IMG" | _filter_qemu_io
> +    $QEMU_IO -c "$raw_cmd" -f raw "$TEST_IMG.raw" | _filter_qemu_io
> +    _verify_img
> +    _verify_l2_bitmap "$l2_entry_idx"
> +}
> +
> +_reset_img()
> +{
> +    size="$1"
> +    $QEMU_IMG create -f raw "$TEST_IMG.raw" "$size" | _filter_img_create
> +    if [ "$use_backing_file" = "yes" ]; then
> +        $QEMU_IMG create -f raw "$TEST_IMG.base" "$size" | _filter_img_create
> +        $QEMU_IO -c "write -q -P 0xFF 0 $size" -f raw "$TEST_IMG.base" | _filter_qemu_io
> +        $QEMU_IO -c "write -q -P 0xFF 0 $size" -f raw "$TEST_IMG.raw" | _filter_qemu_io
> +        _make_test_img -o extended_l2=on -b "$TEST_IMG.base" "$size"

Semantic conflict with my patches to deprecate omitting -F when creating 
images with -b.  If you don't add '-F $IMGFMT' here, then my series will 
have to do it.

> +    else
> +        _make_test_img -o extended_l2=on "$size"
> +    fi
> +}
> +
> +# Test that writing to an image with subclusters produces the expected
> +# results, in images with and without backing files
> +for use_backing_file in yes no; do
> +    echo
> +    echo "### Standard write tests (backing file: $use_backing_file) ###"
> +    echo
> +    _reset_img 1M
> +    ### Write subcluster #0 (beginning of subcluster) ###
> +    alloc="0"; zero=""
> +    _test_write 'write -q -P 1 0 1k'
> +
> +    ### Write subcluster #1 (middle of subcluster) ###
> +    alloc="0 1"; zero=""
> +    _test_write 'write -q -P 2 3k 512'
> +
> +    ### Write subcluster #2 (end of subcluster) ###
> +    alloc="0 1 2"; zero=""
> +    _test_write 'write -q -P 3 5k 1k'
> +
> +    ### Write subcluster #3 (full subcluster) ###
> +    alloc="0 1 2 3"; zero=""
> +    _test_write 'write -q -P 4 6k 2k'
> +
> +    ### Write subclusters #4-6 (full subclusters) ###
> +    alloc="`seq 0 6`"; zero=""

More places where `` could be changed to $()

> +    _test_write 'write -q -P 5 8k 6k'
> +
> +    ### Write subclusters #7-9 (partial subclusters) ###
> +    alloc="`seq 0 9`"; zero=""
> +    _test_write 'write -q -P 6 15k 4k'
> +
> +    ### Write subcluster #16 (partial subcluster) ###
> +    alloc="`seq 0 9` 16"; zero=""
> +    _test_write 'write -q -P 7 32k 1k'
> +
> +    ### Write subcluster #31-#33 (cluster overlap) ###
> +    alloc="`seq 0 9` 16 31"; zero=""
> +    _test_write 'write -q -P 8 63k 4k'
> +    alloc="0 1" ; zero=""
> +    _verify_l2_bitmap 1
> +
> +    ### Zero subcluster #1
> +    alloc="0 `seq 2 9` 16 31"; zero="1"
> +    _test_write 'write -q -z 2k 2k'
> +
> +    ### Zero cluster #0
> +    alloc=""; zero="`seq 0 31`"
> +    _test_write 'write -q -z 0 64k'
> +
> +    ### Fill cluster #0 with data
> +    alloc="`seq 0 31`"; zero=""
> +    _test_write 'write -q -P 9 0 64k'
> +
> +    ### Zero and unmap half of cluster #0 (this won't unmap it)
> +    alloc="`seq 16 31`"; zero="`seq 0 15`"
> +    _test_write 'write -q -z -u 0 32k'
> +
> +    ### Zero and unmap cluster #0
> +    alloc=""; zero="`seq 0 31`"
> +    _test_write 'write -q -z -u 0 64k'
> +
> +    ### Write subcluster #1 (middle of subcluster)
> +    alloc="1"; zero="0 `seq 2 31`"
> +    _test_write 'write -q -P 10 3k 512'
> +
> +    ### Fill cluster #0 with data
> +    alloc="`seq 0 31`"; zero=""
> +    _test_write 'write -q -P 11 0 64k'
> +
> +    ### Discard cluster #0
> +    alloc=""; zero="`seq 0 31`"
> +    _test_write 'discard -q 0 64k'
> +
> +    ### Write compressed data to cluster #0
> +    alloc=""; zero=""
> +    _test_write 'write -q -c -P 12 0 64k'
> +
> +    ### Write subcluster #2 (middle of subcluster)
> +    alloc="`seq 0 31`"; zero=""
> +    _test_write 'write -q -P 13 3k 512'
> +done

Looks like a nice sequence to give a lot of coverage to the various cases.

> +
> +# calculate_l2_meta() checks if none of the clusters affected by a
> +# write operation need COW or changes to their L2 metadata and simply
> +# returns when they don't. This is a test for that optimization.
> +# Here clusters #0-#3 are overwritten but only #1 and #2 need changes.
> +echo
> +echo '### Overwriting several clusters without COW ###'
> +echo
> +use_backing_file="no" _reset_img 1M
> +# Write cluster #0, subclusters #12-#31
> +alloc="`seq 12 31`"; zero=""
> +_test_write 'write -q 24k 40k' 0
> +
> +# Write cluster #1, subcluster #13
> +alloc="13"; zero=""
> +_test_write 'write -q 90k 2k' 1
> +
> +# Zeroize cluster #2, subcluster #14
> +alloc="14"; zero=""
> +_test_write 'write -q 156k 2k' 2
> +alloc=""; zero="14"
> +_test_write 'write -q -z 156k 2k' 2
> +
> +# Write cluster #3, subclusters #15-#31
> +alloc="`seq 0 16`"; zero=""
> +_test_write 'write -q 192k 34k' 3
> +
> +# Write from cluster #0, subcluster #12 to cluster #3, subcluster #11
> +alloc="`seq 12 31`"; zero=""
> +_test_write 'write -q 24k 192k' 0
> +
> +alloc="`seq 0 31`"; zero=""
> +_verify_l2_bitmap 1
> +_verify_l2_bitmap 2
> +
> +alloc="`seq 0 16`"; zero=""
> +_verify_l2_bitmap 3
> +
> +# Test different patterns of writing zeroes
> +for use_backing_file in yes no; do
> +    echo
> +    echo "### Writing zeroes 1: unallocated clusters (backing file: $use_backing_file) ###"
> +    echo
> +    # Note that the image size is not a multiple of the cluster size
> +    _reset_img 2083k
> +
> +    # Cluster-aligned request from clusters #0 to #2
> +    alloc=""; zero="`seq 0 31`"
> +    _test_write 'write -q -z 0 192k' 0
> +    _verify_l2_bitmap 1
> +    _verify_l2_bitmap 2
> +
> +    # Subcluster-aligned request from clusters #3 to #5
> +    alloc=""; zero="`seq 16 31`"
> +    _test_write 'write -q -z 224k 128k' 3
> +    alloc=""; zero="`seq 0 31`"
> +    _verify_l2_bitmap 4
> +    alloc=""; zero="`seq 0 15`"
> +    _verify_l2_bitmap 5
> +
> +    # Unaligned request from clusters #6 to #8
> +    if [ "$use_backing_file" = "yes" ]; then
> +        alloc="15"; zero="`seq 16 31`" # copy-on-write happening here
> +    else
> +        alloc=""; zero="`seq 15 31`"
> +    fi
> +    _test_write 'write -q -z 415k 128k' 6
> +    alloc=""; zero="`seq 0 31`"
> +    _verify_l2_bitmap 7
> +    if [ "$use_backing_file" = "yes" ]; then
> +        alloc="15"; zero="`seq 0 14`" # copy-on-write happening here
> +    else
> +        alloc=""; zero="`seq 0 15`"
> +    fi
> +    _verify_l2_bitmap 8
> +
> +    echo
> +    echo "### Writing zeroes 2: allocated clusters (backing file: $use_backing_file) ###"
> +    echo
> +    alloc="`seq 0 31`"; zero=""
> +    _test_write 'write -q -P 1 576k 576k' 9
> +    _verify_l2_bitmap 10
> +    _verify_l2_bitmap 11
> +    _verify_l2_bitmap 12
> +    _verify_l2_bitmap 13
> +    _verify_l2_bitmap 14
> +    _verify_l2_bitmap 15
> +    _verify_l2_bitmap 16
> +    _verify_l2_bitmap 17
> +
> +    # Cluster-aligned request from clusters #9 to #11
> +    alloc=""; zero="`seq 0 31`"
> +    _test_write 'write -q -z 576k 192k' 9
> +    _verify_l2_bitmap 10
> +    _verify_l2_bitmap 11
> +
> +    # Subcluster-aligned request from clusters #12 to #14
> +    alloc="`seq 0 15`"; zero="`seq 16 31`"
> +    _test_write 'write -q -z 800k 128k' 12
> +    alloc=""; zero="`seq 0 31`"
> +    _verify_l2_bitmap 13
> +    alloc="`seq 16 31`"; zero="`seq 0 15`"
> +    _verify_l2_bitmap 14
> +
> +    # Unaligned request from clusters #15 to #17
> +    alloc="`seq 0 15`"; zero="`seq 16 31`"
> +    _test_write 'write -q -z 991k 128k' 15
> +    alloc=""; zero="`seq 0 31`"
> +    _verify_l2_bitmap 16
> +    alloc="`seq 15 31`"; zero="`seq 0 14`"
> +    _verify_l2_bitmap 17
> +
> +    echo
> +    echo "### Writing zeroes 3: compressed clusters (backing file: $use_backing_file) ###"
> +    echo
> +    alloc=""; zero=""
> +    for c in `seq 18 28`; do
> +        _test_write "write -q -c -P 2 $(($c*64))k 64k" $c
> +    done
> +
> +    # Cluster-aligned request from clusters #18 to #20
> +    alloc=""; zero="`seq 0 31`"
> +    _test_write 'write -q -z 1152k 192k' 18
> +    _verify_l2_bitmap 19
> +    _verify_l2_bitmap 20
> +
> +    # Subcluster-aligned request from clusters #21 to #23.
> +    # We cannot partially zero a compressed cluster so the code
> +    # returns -ENOTSUP, which means copy-on-write of the compressed
> +    # data and fill the rest with actual zeroes on disk.
> +    # TODO: cluster #22 should use the 'all zeroes' bits.
> +    alloc="`seq 0 31`"; zero=""
> +    _test_write 'write -q -z 1376k 128k' 21
> +    _verify_l2_bitmap 22
> +    _verify_l2_bitmap 23

Hmm - this matches the question in 28/32 about whether we are handling 
sub-cluster-aligned requests correctly.  Is it merely a case that we 
aren't telling the block layer our correct preferred alignment for zero 
requests?
[...]

> +    # Unaligned request from clusters #24 to #26
> +    # In this case QEMU internally sends a 1k request followed by a
> +    # subcluster-aligned 128k request. The first request decompresses
> +    # cluster #24, but that's not enough to perform efficiently the
> +    # second request because it partially writes to cluster #26 (which

s/perform efficiently the second request/perform the second request 
efficiently/

> +
> +# Test that corrupted L2 entries are detected in both read and write
> +# operations
> +for corruption_test_cmd in read write; do
> +    echo
> +    echo "### Corrupted L2 entries - $corruption_test_cmd test (allocated) ###"
> +    echo
> +    echo "# 'cluster is zero' bit set on the standard cluster descriptor"
> +    echo
> +    # We actually don't consider this a corrupted image.
> +    # The 'cluster is zero' bit is unused is unused in extended L2 entries

doubled 'is unused'

> +    # so QEMU ignores it.
> +    # TODO: maybe treat the image as corrupted and make qemu-img check fix it?
> +    _make_test_img -o extended_l2=on 1M
> +    $QEMU_IO -c 'write -q -P 0x11 0 2k' "$TEST_IMG"
> +    poke_file "$TEST_IMG" $(($l2_offset+7)) "\x01"
> +    alloc="0"; zero=""
> +    _verify_l2_bitmap 0
> +    $QEMU_IO -c "$corruption_test_cmd -q -P 0x11 0 1k" "$TEST_IMG"
> +    if [ "$corruption_test_cmd" = "write" ]; then
> +        alloc="0"; zero=""
> +    fi
> +    _verify_l2_bitmap 0
> +
> +    echo
> +    echo "# Both 'subcluster is zero' and 'subcluster is allocated' bits set"
> +    echo
> +    _make_test_img -o extended_l2=on 1M
> +    # Write from the middle of cluster #0 to the middle of cluster #2
> +    $QEMU_IO -c 'write -q 32k 128k' "$TEST_IMG"
> +    # Corrupt the L2 entry from cluster #1
> +    poke_file "$TEST_IMG" $(($l2_offset+24)) "\x00\x00\x00\x01"
> +    alloc="`seq 0 31`"; zero="0"
> +    _verify_l2_bitmap 1
> +    $QEMU_IO -c "$corruption_test_cmd 0 192k" "$TEST_IMG"
> +
> +    echo
> +    echo "### Corrupted L2 entries - $corruption_test_cmd test (unallocated) ###"
> +    echo
> +    echo "# 'cluster is zero' bit set on the standard cluster descriptor"
> +    echo
> +    # We actually don't consider this a corrupted image.
> +    # The 'cluster is zero' bit is unused is unused in extended L2 entries

and again

> +    # so QEMU ignores it.
> +    # TODO: maybe treat the image as corrupted and make qemu-img check fix it?
> +    _make_test_img -o extended_l2=on 1M
> +    # We want to modify the (empty) L2 entry from cluster #0,
> +    # but we write to #4 in order to initialize the L2 table first
> +    $QEMU_IO -c 'write -q 256k 1k' "$TEST_IMG"
> +    poke_file "$TEST_IMG" $(($l2_offset+7)) "\x01"
> +    alloc=""; zero=""
> +    _verify_l2_bitmap 0
> +    $QEMU_IO -c "$corruption_test_cmd -q 0 1k" "$TEST_IMG"
> +    if [ "$corruption_test_cmd" = "write" ]; then
> +        alloc="0"; zero=""
> +    fi
> +    _verify_l2_bitmap 0
> +
> +    echo
> +    echo "# 'subcluster is allocated' bit set"
> +    echo
> +    _make_test_img -o extended_l2=on 1M
> +    # We want to corrupt the (empty) L2 entry from cluster #0,
> +    # but we write to #4 in order to initialize the L2 table first
> +    $QEMU_IO -c 'write -q 256k 1k' "$TEST_IMG"
> +    poke_file "$TEST_IMG" $(($l2_offset+15)) "\x01"
> +    alloc="0"; zero=""
> +    _verify_l2_bitmap 0
> +    $QEMU_IO -c "$corruption_test_cmd 0 1k" "$TEST_IMG"
> +
> +    echo
> +    echo "# Both 'subcluster is zero' and 'subcluster is allocated' bits set"
> +    echo
> +    _make_test_img -o extended_l2=on 1M
> +    # We want to corrupt the (empty) L2 entry from cluster #1,
> +    # but we write to #4 in order to initialize the L2 table first
> +    $QEMU_IO -c 'write -q 256k 1k' "$TEST_IMG"
> +    # Corrupt the L2 entry from cluster #1
> +    poke_file "$TEST_IMG" $(($l2_offset+24)) "\x00\x00\x00\x01\x00\x00\x00\x01"

would statements like this be any easier with poke_file_be?

> +    alloc="0"; zero="0"
> +    _verify_l2_bitmap 1
> +    $QEMU_IO -c "$corruption_test_cmd 0 192k" "$TEST_IMG"
> +
> +    echo
> +    echo "### Compressed cluster with subcluster bitmap != 0 - $corruption_test_cmd test ###"
> +    echo
> +    # We actually don't consider this a corrupted image.
> +    # The bitmap in compressed clusters is unused so QEMU should just ignore it.
> +    _make_test_img -o extended_l2=on 1M
> +    $QEMU_IO -c 'write -q -P 11 -c 0 64k' "$TEST_IMG"
> +    # Change the L2 bitmap to allocate subcluster #31 and zeroize subcluster #0
> +    poke_file "$TEST_IMG" $(($l2_offset+11)) "\x01\x80"
> +    alloc="31"; zero="0"
> +    _verify_l2_bitmap 0
> +    $QEMU_IO -c "$corruption_test_cmd -P 11 0 64k" "$TEST_IMG" | _filter_qemu_io
> +    # Writing allocates a new uncompressed cluster so we get a new bitmap
> +    if [ "$corruption_test_cmd" = "write" ]; then
> +        alloc="`seq 0 31`"; zero=""
> +    fi
> +    _verify_l2_bitmap 0
> +done
> +
> +echo
> +echo "### Image creation options ###"
> +echo
> +echo "# cluster_size < 16k"
> +_make_test_img -o extended_l2=on,cluster_size=8k 1M
> +
> +# TODO: allow preallocation with backing files when subclusters are used
> +echo "# backing file and preallocation=metadata"
> +_make_test_img -o extended_l2=on,preallocation=metadata -b "$TEST_IMG.base" 1M
> +
> +echo "# backing file and preallocation=falloc"
> +_make_test_img -o extended_l2=on,preallocation=falloc -b "$TEST_IMG.base" 1M
> +
> +echo "# backing file and preallocation=full"
> +_make_test_img -o extended_l2=on,preallocation=full -b "$TEST_IMG.base" 1M
> +
> +echo
> +echo "### qemu-img measure ###"
> +echo
> +echo "# 512MB, extended_l2=off" # This needs one L2 table
> +$QEMU_IMG measure --size 512M -O qcow2 -o extended_l2=off
> +echo "# 512MB, extended_l2=on"  # This needs two L2 tables
> +$QEMU_IMG measure --size 512M -O qcow2 -o extended_l2=on
> +
> +echo "# 16K clusters, 64GB, extended_l2=off" # This needs one full L1 table cluster
> +$QEMU_IMG measure --size 64G -O qcow2 -o cluster_size=16k,extended_l2=off
> +echo "# 16K clusters, 64GB, extended_l2=on"  # This needs two full L2 table clusters
> +$QEMU_IMG measure --size 64G -O qcow2 -o cluster_size=16k,extended_l2=on
> +
> +echo "# 8k clusters" # This should fail
> +$QEMU_IMG measure --size 1M -O qcow2 -o cluster_size=8k,extended_l2=on
> +
> +echo "# 1024 TB" # Maximum allowed size with extended_l2=on and 64K clusters
> +$QEMU_IMG measure --size 1024T -O qcow2 -o extended_l2=on
> +echo "# 1025 TB" # This should fail
> +$QEMU_IMG measure --size 1025T -O qcow2 -o extended_l2=on
> +
> +echo
> +echo "### qemu-img amend ###"
> +echo
> +_make_test_img -o extended_l2=on 1M
> +$QEMU_IMG amend -o extended_l2=off "$TEST_IMG"
> +
> +_make_test_img -o extended_l2=off 1M
> +$QEMU_IMG amend -o extended_l2=on "$TEST_IMG"

When we know we currently fail, should we write:

$QEMU_IMG ... && echo "unexpected pass"

to track exit status in addition to output comparison?

> +
> +echo
> +echo "### Test copy-on-write on an image with snapshots ###"
> +echo
> +_make_test_img -o extended_l2=on 1M
> +
> +# For each cluster from #0 to #9 this loop zeroes subcluster #7
> +# and allocates subclusters #13 and #18.
> +alloc="13 18"; zero="7"
> +for c in `seq 0 9`; do
> +    $QEMU_IO -c "write -q -z $((64*$c+14))k 2k" \
> +             -c "write -q -P $((0xd0+$c)) $((64*$c+26))k 2k" \
> +             -c "write -q -P $((0xe0+$c)) $((64*$c+36))k 2k" "$TEST_IMG"
> +    _verify_l2_bitmap "$c"
> +done
> +
> +# Create a snapshot and set l2_offset to the new L2 table
> +$QEMU_IMG snapshot -c snap1 "$TEST_IMG"
> +l2_offset=1114112 # 0x110000
> +
> +# Write different patterns to each one of the clusters
> +# in order to see how copy-on-write behaves in each case.
> +$QEMU_IO -c "write -q -P 0xf0 $((64*0+30))k 1k" \
> +         -c "write -q -P 0xf1 $((64*1+20))k 1k" \
> +         -c "write -q -P 0xf2 $((64*2+40))k 1k" \
> +         -c "write -q -P 0xf3 $((64*3+26))k 1k" \
> +         -c "write -q -P 0xf4 $((64*4+14))k 1k" \
> +         -c "write -q -P 0xf5 $((64*5+1))k  1k" \
> +         -c "write -q -z      $((64*6+30))k 3k" \
> +         -c "write -q -z      $((64*7+26))k 2k" \
> +         -c "write -q -z      $((64*8+26))k 1k" \
> +         -c "write -q -z      $((64*9+12))k 1k" \
> +         "$TEST_IMG"
> +alloc="`seq 13 18`"; zero="7" _verify_l2_bitmap 0
> +alloc="`seq 10 18`"; zero="7" _verify_l2_bitmap 1
> +alloc="`seq 13 20`"; zero="7" _verify_l2_bitmap 2
> +alloc="`seq 13 18`"; zero="7" _verify_l2_bitmap 3
> +alloc="`seq 7 18`";  zero=""  _verify_l2_bitmap 4
> +alloc="`seq 0 18`";  zero=""  _verify_l2_bitmap 5
> +alloc="13 18"; zero="7 15 16" _verify_l2_bitmap 6
> +alloc="18";       zero="7 13" _verify_l2_bitmap 7
> +alloc="`seq 13 18`"; zero="7" _verify_l2_bitmap 8
> +alloc="13 18";     zero="6 7" _verify_l2_bitmap 9
> +

Nice - overall pretty thorough!

> +# success, all done
> +echo "*** done"
> +rm -f $seq.full
> +status=0
> diff --git a/tests/qemu-iotests/271.out b/tests/qemu-iotests/271.out
> new file mode 100644
> index 0000000000..6ac53d5e10
> --- /dev/null


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org