[libvirt] [PATCH v2] test_driver: implement virDomainGetDiskErrors

[Ilias Stamatis]

On Mon, May 13, 2019 at 2:38 PM Michal Privoznik <mprivozn at redhat.com> wrote:
>
> On 5/13/19 1:26 AM, Ilias Stamatis wrote:
> > Return the number of disks present in the configuration of the test
> > domain when called with @errors as NULL and @maxerrors as 0.
> >
> > Otherwise report an error for every second disk, assigning available
> > error codes in a cyclic order.
> >
> > Signed-off-by: Ilias Stamatis <stamatis.iliass at gmail.com>
> > ---
> >   src/test/test_driver.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 42 insertions(+)
> >
> > diff --git a/src/test/test_driver.c b/src/test/test_driver.c
> > index a06d1fc402..527c2f5d3b 100644
> > --- a/src/test/test_driver.c
> > +++ b/src/test/test_driver.c
> > @@ -3046,6 +3046,47 @@ static int testDomainSetAutostart(virDomainPtr domain,
> >       return 0;
> >   }
> >
> > +static int testDomainGetDiskErrors(virDomainPtr dom,
> > +                                   virDomainDiskErrorPtr errors,
> > +                                   unsigned int maxerrors,
> > +                                   unsigned int flags)
> > +{
> > +    virDomainObjPtr vm = NULL;
> > +    int ret = -1;
> > +    size_t i;
> > +    int n = 0;
> > +    int codes[] = {VIR_DOMAIN_DISK_ERROR_UNSPEC, VIR_DOMAIN_DISK_ERROR_NO_SPACE};
> > +    size_t ncodes = sizeof(codes) / sizeof(codes[0]);
>
> We have ARRAY_CARDINALITY() for this.
> Also, there's no need to create @codes array as we'll see later.

Aah, okay, I wasn't aware of this macro!

>
> > +
> > +    virCheckFlags(0, -1);
> > +
> > +    if (!(vm = testDomObjFromDomain(dom)))
> > +        goto cleanup;
> > +
> > +    if (virDomainObjCheckActive(vm) < 0)
> > +        goto cleanup;
> > +
> > +    if (!errors) {
> > +        ret = vm->def->ndisks;
>
> Tiny nitpick, we tend to put the longer body first, which in this case
> is the else branch.

Hmm, I would normally do it like that but I noticed this in the "Curly
braces" section of the Contributor guidelines [1]:

"""Also, if the else block is much shorter than the if block, consider
negating the if-condition and swapping the bodies, putting the short
block first and making the longer, multi-line block be the else
block."""

So what is the case?

>
> > +    } else {
> > +        for (i = 1; i < vm->def->ndisks && n < maxerrors; i += 2) {
> > +            if (VIR_STRDUP(errors[n].disk, vm->def->disks[i]->dst) < 0)
> > +                goto cleanup;
> > +            errors[n].error = codes[n % ncodes];
>
> This can be simplified. This enum in question is guaranteed to have
> continuous items and _LAST to be the last item. Hence, this can be
> rewritten as:
>
> errors[i].error = (i % (VIR_DOMAIN_DISK_ERROR_LAST - 1)) + 1;
>

I am aware of this but I wasn't sure if it would be very clean if I
started adding -1s and +1s in places.

> But if we want to simplify it a little bit more (so that
> VIR_DOMAIN_DISK_ERROR_NONE is possible too) we can do it like this:
>
> errors[i].error = i % VIR_DOMAIN_DISK_ERROR_LAST;

Hmm, in the documentation for this function [2] it is stated that:

"""Disks with no error will not be returned in the @errors array."""

So it seems to me that VIR_DOMAIN_DISK_ERROR_NONE shouldn't be
included. What do you think?

>
> This immediatelly drops @codes, @ncodes and @n variables.
> Also, there's MIN() macro ;-)

Cool, but where exactly do you suggest using MIN() here? Or you're
just mentioning it?

> Yeah, libvirt has a lot of marcos and helpers and it's not obvious at
> the first glance, but I guess that's like so with every bigger project,
> isn't it?

Yes, and I find these wrappers very useful / handy ;)
>
> > +            n++;
> > +        }
> > +        ret = n;
> > +    }
> > +
> > + cleanup:
> > +    virDomainObjEndAPI(&vm);
> > +    if (ret < 0) {
> > +        for (i = 0; i < n; i++)
> > +            VIR_FREE(errors[i].disk);
> > +    }
> > +    return ret;
> > +}
> > +
> >   static char *testDomainGetSchedulerType(virDomainPtr domain ATTRIBUTE_UNUSED,
> >                                           int *nparams)
> >   {
> > @@ -6832,6 +6873,7 @@ static virHypervisorDriver testHypervisorDriver = {
> >       .domainUndefineFlags = testDomainUndefineFlags, /* 0.9.4 */
> >       .domainGetAutostart = testDomainGetAutostart, /* 0.3.2 */
> >       .domainSetAutostart = testDomainSetAutostart, /* 0.3.2 */
> > +    .domainGetDiskErrors = testDomainGetDiskErrors, /* 5.4.0 */
> >       .domainGetSchedulerType = testDomainGetSchedulerType, /* 0.3.2 */
> >       .domainGetSchedulerParameters = testDomainGetSchedulerParameters, /* 0.3.2 */
> >       .domainGetSchedulerParametersFlags = testDomainGetSchedulerParametersFlags, /* 0.9.2 */
>
>
> I'm cleaning the patch as outlined, ACKing and pushing.

Sure, or I could fix it if you wanted.

Thank you very much!
Ilias

[1] https://libvirt.org/hacking.html#curly_braces
[2] https://libvirt.org/html/libvirt-libvirt-domain.html#virDomainGetDiskErrors
>
> Michal