Re: [PATCH v2 6/6] iotests: Add test 291 to for qemu-img bitmap coverage

[Max Reitz <mreitz@redhat.com>]

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On 21.04.20 23:20, Eric Blake wrote:
> Add a new test covering the 'qemu-img bitmap' subcommand, as well as
> 'qemu-img convert --bitmaps', both added in recent patches.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  tests/qemu-iotests/291     | 103 +++++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/291.out |  78 ++++++++++++++++++++++++++++
>  tests/qemu-iotests/group   |   1 +
>  3 files changed, 182 insertions(+)
>  create mode 100755 tests/qemu-iotests/291
>  create mode 100644 tests/qemu-iotests/291.out
> 
> diff --git a/tests/qemu-iotests/291 b/tests/qemu-iotests/291
> new file mode 100755
> index 000000000000..77713c0cfea7
> --- /dev/null
> +++ b/tests/qemu-iotests/291

[...]

> +echo
> +echo "=== Bitmap preservation not possible to non-qcow2 ==="
> +echo
> +
> +mv "$TEST_IMG" "$TEST_IMG.orig"

“mv” doesn’t work images with external data files.

(ORIG_IMG=$TEST_IMG; TEST_IMG="$TEST_IMG".orig should work)

> +$QEMU_IMG convert --bitmaps -O raw "$TEST_IMG.orig" "$TEST_IMG"
> +
> +echo
> +echo "=== Convert with bitmap preservation ==="
> +echo
> +
> +# Only bitmaps from the active layer are copied

That’s kind of obvious when you think about (whenever an image is
attached to a VM, only the active layer’s bitmaps are visible, not those
from the backing chain), but maybe this should be noted in the
documentation?

> +$QEMU_IMG convert --bitmaps -O qcow2 "$TEST_IMG.orig" "$TEST_IMG"
> +$QEMU_IMG info "$TEST_IMG" | _filter_img_info --format-specific
> +# But we can also merge in bitmaps from other layers
> +$QEMU_IMG bitmap --add --disabled -f $IMGFMT "$TEST_IMG" b0
> +$QEMU_IMG bitmap --add -f $IMGFMT "$TEST_IMG" tmp
> +$QEMU_IMG bitmap --merge b0 -b "$TEST_IMG.base" -F $IMGFMT "$TEST_IMG" tmp
> +$QEMU_IMG bitmap --merge tmp "$TEST_IMG" b0
> +$QEMU_IMG bitmap --remove -f $IMGFMT "$TEST_IMG" tmp

Why do we need tmp here?  Can’t we just merge base’s b0 directly into
$TEST_IMG’s b0?

[...]

> diff --git a/tests/qemu-iotests/291.out b/tests/qemu-iotests/291.out
> new file mode 100644
> index 000000000000..d716c0c7cc0b
> --- /dev/null
> +++ b/tests/qemu-iotests/291.out

[...]

> +=== Check bitmap contents ===
> +
> +[{ "start": 0, "length": 3145728, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
> +{ "start": 3145728, "length": 1048576, "depth": 0, "zero": false, "data": false},
> +{ "start": 4194304, "length": 6291456, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
> +[{ "start": 0, "length": 1048576, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
> +{ "start": 1048576, "length": 1048576, "depth": 0, "zero": false, "data": false},
> +{ "start": 2097152, "length": 8388608, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
> +[{ "start": 0, "length": 2097152, "depth": 0, "zero": false, "data": true, "offset": OFFSET},
> +{ "start": 2097152, "length": 1048576, "depth": 0, "zero": false, "data": false},
> +{ "start": 3145728, "length": 7340032, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]

Am I looking at this wrong or does the bitmap data seem to be inverted?
 Everywhere where I’d expect the bitmaps to be cleared, this map reports
data=true, whereas where I’d expect them to be set, it reports data=false.

I suppose that’s intentional, but can you explain this behavior to me?

Max

> +*** done


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