Re: [PATCH 9/9] tests/qtest/migration: Add a test for mapped-ram with passing of fds

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Apr 26, 2024 at 11:20:42AM -0300, Fabiano Rosas wrote:
> Add a multifd test for mapped-ram with passing of fds into QEMU. This
> is how libvirt will consume the feature.
> 
> There are a couple of details to the fdset mechanism:
> 
> - multifd needs two distinct file descriptors (not duplicated with
>   dup()) on the outgoing side so it can enable O_DIRECT only on the
>   channels that write with alignment. The dup() system call creates
>   file descriptors that share status flags, of which O_DIRECT is one.
> 
>   the incoming side doesn't set O_DIRECT, so it can dup() fds and
>   therefore can receive only one in the fdset.
> 
> - the open() access mode flags used for the fds passed into QEMU need
>   to match the flags QEMU uses to open the file. Currently O_WRONLY
>   for src and O_RDONLY for dst.
> 
> O_DIRECT is not supported on all systems/filesystems, so run the fdset
> test without O_DIRECT if that's the case. The migration code should
> still work in that scenario.

If O_DIRECT is not supported, then we're not setting 'direct-io',
and thus isn't this test just duplicating coverage of existing
tests ?

If this test is specifically to cover O_DIRECT, then I'd just
#ifdef the entire thing with O_DIRECT.

> 
> Signed-off-by: Fabiano Rosas <farosas@suse.de>
> ---
>  tests/qtest/migration-test.c | 90 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 90 insertions(+)
> 
> diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> index 512b7ede8b..d83f1bdd4f 100644
> --- a/tests/qtest/migration-test.c
> +++ b/tests/qtest/migration-test.c
> @@ -2331,8 +2331,93 @@ static void test_multifd_file_mapped_ram_dio(void)
>      test_file_common(&args, true);
>  }
>  
> +static void migrate_multifd_mapped_ram_fdset_dio_end(QTestState *from,
> +                                                    QTestState *to,
> +                                                    void *opaque)
> +{
> +    QDict *resp;
> +    QList *fdsets;
> +
> +    file_offset_finish_hook(from, to, opaque);
> +
> +    /*
> +     * Check that we removed the fdsets after migration, otherwise a
> +     * second migration would fail due to too many fdsets.
> +     */
> +
> +    resp = qtest_qmp(from, "{'execute': 'query-fdsets', "
> +                     "'arguments': {}}");
> +    g_assert(qdict_haskey(resp, "return"));
> +    fdsets = qdict_get_qlist(resp, "return");
> +    g_assert(fdsets && qlist_empty(fdsets));
> +}
>  #endif /* O_DIRECT */
>  
> +#ifndef _WIN32
> +static void *migrate_multifd_mapped_ram_fdset(QTestState *from, QTestState *to)
> +{
> +    g_autofree char *file = g_strdup_printf("%s/%s", tmpfs, FILE_TEST_FILENAME);
> +    int fds[3];
> +    int src_flags = O_WRONLY;
> +
> +    file_dirty_offset_region();
> +
> +    /* main outgoing channel: no O_DIRECT */
> +    fds[0] = open(file, src_flags, 0660);
> +    assert(fds[0] != -1);
> +
> +    qtest_qmp_fds_assert_success(from, &fds[0], 1, "{'execute': 'add-fd', "
> +                                 "'arguments': {'fdset-id': 1}}");
> +
> +#ifdef O_DIRECT
> +    src_flags |= O_DIRECT;
> +
> +    /* secondary outgoing channels */
> +    fds[1] = open(file, src_flags, 0660);
> +    assert(fds[1] != -1);
> +
> +    qtest_qmp_fds_assert_success(from, &fds[1], 1, "{'execute': 'add-fd', "
> +                                 "'arguments': {'fdset-id': 1}}");
> +
> +    /* incoming channel */
> +    fds[2] = open(file, O_CREAT | O_RDONLY, 0660);
> +    assert(fds[2] != -1);
> +
> +    qtest_qmp_fds_assert_success(to, &fds[2], 1, "{'execute': 'add-fd', "
> +                                 "'arguments': {'fdset-id': 1}}");
> +
> +    migrate_multifd_mapped_ram_dio_start(from, to);
> +#else
> +    migrate_multifd_mapped_ram_start(from, to);
> +#endif
> +
> +    return NULL;
> +}
> +
> +static void test_multifd_file_mapped_ram_fdset(void)
> +{
> +    g_autofree char *uri = g_strdup_printf("file:/dev/fdset/1,offset=%d",
> +                                           FILE_TEST_OFFSET);
> +    MigrateCommon args = {
> +        .connect_uri = uri,
> +        .listen_uri = "defer",
> +        .start_hook = migrate_multifd_mapped_ram_fdset,
> +#ifdef O_DIRECT
> +        .finish_hook = migrate_multifd_mapped_ram_fdset_dio_end,
> +#endif
> +    };
> +
> +#ifdef O_DIRECT
> +    if (!probe_o_direct_support(tmpfs)) {
> +        g_test_skip("Filesystem does not support O_DIRECT");
> +        return;
> +    }
> +#endif
> +
> +    test_file_common(&args, true);
> +}
> +#endif /* _WIN32 */
> +
>  static void test_precopy_tcp_plain(void)
>  {
>      MigrateCommon args = {
> @@ -3761,6 +3846,11 @@ int main(int argc, char **argv)
>                         test_multifd_file_mapped_ram_dio);
>  #endif
>  
> +#ifndef _WIN32
> +    qtest_add_func("/migration/multifd/file/mapped-ram/fdset",
> +                   test_multifd_file_mapped_ram_fdset);
> +#endif
> +
>  #ifdef CONFIG_GNUTLS
>      migration_test_add("/migration/precopy/unix/tls/psk",
>                         test_precopy_unix_tls_psk);
> -- 
> 2.35.3
> 

With regards,
Daniel
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