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Date: Wed, 26 Apr 2017 14:30:46 +0200
From: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20170426123046.GC4538@noname.str.redhat.com>
References: <20170426033413.17192-1-famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v15 11/21] iotests: 085: Avoid image
 locking conflict
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To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, eblake@redhat.com, Max Reitz <mreitz@redhat.com>, qemu-block@nongnu.org

Am 26.04.2017 um 05:34 hat Fam Zheng geschrieben:
> In the case where we test the expected error when a blockdev-snapshot
> target already has a backing image, the backing chain is opened multiple
> times. This will be a problem when we use image locking, so use a
> different backing file that is not already open.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  tests/qemu-iotests/085     | 34 ++++++++++++++++++++--------------
>  tests/qemu-iotests/085.out |  3 ++-
>  2 files changed, 22 insertions(+), 15 deletions(-)
> 
> diff --git a/tests/qemu-iotests/085 b/tests/qemu-iotests/085
> index c53e97f..cc6efd8 100755
> --- a/tests/qemu-iotests/085
> +++ b/tests/qemu-iotests/085
> @@ -45,7 +45,7 @@ _cleanup()
>          rm -f "${TEST_DIR}/${i}-${snapshot_virt0}"
>          rm -f "${TEST_DIR}/${i}-${snapshot_virt1}"
>      done
> -    rm -f "${TEST_IMG}.1" "${TEST_IMG}.2"
> +    rm -f "${TEST_IMG}" "${TEST_IMG}.1" "${TEST_IMG}.2" "${TEST_IMG}.base"
>  
>  }
>  trap "_cleanup; exit \$status" 0 1 2 3 15
> @@ -87,24 +87,26 @@ function create_group_snapshot()
>  }
>  
>  # ${1}: unique identifier for the snapshot filename
> -# ${2}: true: open backing images; false: don't open them (default)
> +# ${2}: extra_params to the blockdev-add command
> +# ${3}: filename
> +function do_blockdev_add()
> +{
> +    cmd="{ 'execute': 'blockdev-add', 'arguments':
> +           { 'driver': 'qcow2', 'node-name': 'snap_${1}', ${2}
> +             'file':
> +             { 'driver': 'file', 'filename': '${3}',
> +               'node-name': 'file_${1}' } } }"
> +    _send_qemu_cmd $h "${cmd}" "return"
> +}
> +
> +# ${1}: unique identifier for the snapshot filename
>  function add_snapshot_image()
>  {
> -    if [ "${2}" = "true" ]; then
> -        extra_params=""
> -    else
> -        extra_params="'backing': '', "
> -    fi
>      base_image="${TEST_DIR}/$((${1}-1))-${snapshot_virt0}"
>      snapshot_file="${TEST_DIR}/${1}-${snapshot_virt0}"
>      _make_test_img -b "${base_image}" "$size"
>      mv "${TEST_IMG}" "${snapshot_file}"
> -    cmd="{ 'execute': 'blockdev-add', 'arguments':
> -           { 'driver': 'qcow2', 'node-name': 'snap_${1}', ${extra_params}
> -             'file':
> -             { 'driver': 'file', 'filename': '${snapshot_file}',
> -               'node-name': 'file_${1}' } } }"
> -    _send_qemu_cmd $h "${cmd}" "return"
> +    do_blockdev_add "$1" "'backing': '', " "${snapshot_file}"
>  }
>  
>  # ${1}: unique identifier for the snapshot filename
> @@ -222,7 +224,11 @@ echo === Invalid command - snapshot node has a backing image ===
>  echo
>  
>  SNAPSHOTS=$((${SNAPSHOTS}+1))
> -add_snapshot_image ${SNAPSHOTS} true
> +
> +_make_test_img "$size"
> +mv "${TEST_IMG}" "${TEST_IMG}.base"

The common idiom is:

    TEST_IMG="$TEST_IMG.base" _make_test_img "$size"

This avoids using mv, which is helpful if we ever want to extend the
testcase for non-file protocols.

But I see that you just copied this from add_snapshot_image(), so it's
preexisting and matter for a different patch/series.

> +_make_test_img -b "${TEST_IMG}.base" "$size"
> +do_blockdev_add ${SNAPSHOTS} "" "${TEST_IMG}"
>  blockdev_snapshot ${SNAPSHOTS} error

Kevin