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Re: [PATCH 2/3] iotests: Test qemu-img checksum


From: Hanna Reitz
Subject: Re: [PATCH 2/3] iotests: Test qemu-img checksum
Date: Mon, 7 Nov 2022 12:41:44 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0

On 30.10.22 18:38, Nir Soffer wrote:
On Wed, Oct 26, 2022 at 4:31 PM Hanna Reitz <hreitz@redhat.com> wrote:

    On 01.09.22 16:32, Nir Soffer wrote:
    > Add simple tests creating an image with all kinds of extents,
    different
    > formats, different backing chain, different protocol, and different
    > image options. Since all images have the same guest visible
    content they
    > must have the same checksum.
    >
    > To help debugging in case of failures, the output includes a
    json map of
    > every test image.
    >
    > Signed-off-by: Nir Soffer <nsoffer@redhat.com>
    > ---
    >   tests/qemu-iotests/tests/qemu-img-checksum    | 149
    ++++++++++++++++++
    >   .../qemu-iotests/tests/qemu-img-checksum.out  |  74 +++++++++
    >   2 files changed, 223 insertions(+)
    >   create mode 100755 tests/qemu-iotests/tests/qemu-img-checksum
    >   create mode 100644 tests/qemu-iotests/tests/qemu-img-checksum.out
    >
    > diff --git a/tests/qemu-iotests/tests/qemu-img-checksum
    b/tests/qemu-iotests/tests/qemu-img-checksum
    > new file mode 100755
    > index 0000000000..3a85ba33f2
    > --- /dev/null
    > +++ b/tests/qemu-iotests/tests/qemu-img-checksum
    > @@ -0,0 +1,149 @@
    > +#!/usr/bin/env python3
    > +# group: rw auto quick
    > +#
    > +# Test cases for qemu-img checksum.
    > +#
    > +# Copyright (C) 2022 Red Hat, Inc.
    > +#
    > +# This program is free software; you can redistribute it and/or
    modify
    > +# it under the terms of the GNU General Public License as
    published by
    > +# the Free Software Foundation; either version 2 of the License, or
    > +# (at your option) any later version.
    > +#
    > +# This program is distributed in the hope that it will be useful,
    > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
    > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    > +# GNU General Public License for more details.
    > +#
    > +# You should have received a copy of the GNU General Public License
    > +# along with this program.  If not, see
    <http://www.gnu.org/licenses/>.
    > +
    > +import re
    > +
    > +import iotests
    > +
    > +from iotests import (
    > +    filter_testfiles,
    > +    qemu_img,
    > +    qemu_img_log,
    > +    qemu_io,
    > +    qemu_nbd_popen,
    > +)
    > +
    > +
    > +def checksum_available():
    > +    out = qemu_img("--help").stdout
    > +    return re.search(r"\bchecksum .+ filename\b", out) is not None
    > +
    > +
    > +if not checksum_available():
    > +    iotests.notrun("checksum command not available")
    > +
    > +iotests.script_initialize(
    > +    supported_fmts=["raw", "qcow2"],
    > +    supported_cache_modes=["none", "writeback"],

    It doesn’t work with writeback, though, because it uses -T none below.


Good point


    Which by the way is a heavy cost, because I usually run tests in
    tmpfs,
    where this won’t work.  Is there any way of not doing the -T none
    below?


Testing using tempfs is problematic since you cannot test -T none.In oVirt we alway use /var/tmp which usually uses something that supports direct I/O.

Do we have a way to specify cache mode in the tests, so we can use -T none
only when the option is set?

`./check` has a `-c` option (e.g. `./check -c none`), which lands in `iotests.cachemode`.  That isn’t automatically passed to qemu-img calls, but you can do it manually (i.e. `qemu_img_log("checksum", "-T", iotests.cachemode, disk_top)` instead of `"-T", "none"`).


    > +    supported_protocols=["file", "nbd"],
    > +    required_fmts=["raw", "qcow2"],
    > +)
    > +
    > +print()
    > +print("=== Test images ===")
    > +print()
    > +
    > +disk_raw = iotests.file_path('raw')
    > +qemu_img("create", "-f", "raw", disk_raw, "10m")
    > +qemu_io("-f", "raw",
    > +        "-c", "write -P 0x1 0 2m",      # data
    > +        "-c", "write -P 0x0 2m 2m",     # data with zeroes
    > +        "-c", "write -z 4m 2m",         # zero allocated
    > +        "-c", "write -z -u 6m 2m",      # zero hole
    > +                                        # unallocated
    > +        disk_raw)
    > +print(filter_testfiles(disk_raw))
    > +qemu_img_log("map", "--output", "json", disk_raw)
    > +
    > +disk_qcow2 = iotests.file_path('qcow2')
    > +qemu_img("create", "-f", "qcow2", disk_qcow2, "10m")
    > +qemu_io("-f", "qcow2",
    > +        "-c", "write -P 0x1 0 2m",      # data
    > +        "-c", "write -P 0x0 2m 2m",     # data with zeroes
    > +        "-c", "write -z 4m 2m",         # zero allocated
    > +        "-c", "write -z -u 6m 2m",      # zero hole
    > +                                        # unallocated
    > +        disk_qcow2)
    > +print(filter_testfiles(disk_qcow2))
    > +qemu_img_log("map", "--output", "json", disk_qcow2)

    This isn’t how iotests work, generally.  When run with -qcow2
    -file, it
    should only test qcow2 on file, not raw on file, not raw on nbd.
    Perhaps
    this way this test could even support other formats than qcow2 and
    raw.


For this type of tests, running the same code with raw, qcow2 (and other formats) and using file or nbd is the best way to test this feature - one test verifies all the
use cases.

Yes, I see, but that’s a general thing in the iotests.  The design is such that tests don’t cycle through their test matrix themselves, but that they always only test a single combination of format+protocol on each run, and the user is responsible for cycling through the desired test matrix.

I’m not saying that was definitely the best design decision, but the problem now that if a test cycles through its test matrix by itself, it must also ensure that it is run only once when the user cycles through the same test matrix.  For example, a reasonable run of the iotests consists of `./check -raw`, `./check -qcow2`, and `./check -nbd`.  This test here would then run in all three configurations, but do the same thing every time (specifically, test all of those configurations every time).

So there’s a conflict.  Either the test follows the existing design and only tests a single configuration, as iotests are expected to do, or we have the question of how to deal with the fact that users will run the test suite in multiple configurations, but one run of this test would already cover them all.

I’m not sternly against cycling through the possible combinations right here in the test, but I want to lay out the problems with that approach.

I can change this to use the current format (raw, qcow2, ...), protocol (file, nbd, ...) and cache value (none, writeback), but I'm not sure how this can work with the out files. The output from nbd is different from file. Maybe we need different out files for file and nbd (qemu-img-checksum.file.out, qemu-img-checksum.nbd.out)?

We already have that for the format (e.g. 178.out.{qcow2,raw}).  If you decide to do that, it shouldn’t be too difficult to implement (testrunner.py’s `TestRunner.find_reference()`).  Alternatively, it’s also possible to basically ignore the reference output and verify the expected output right in the test code.

Hanna




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