Re: [libvirt] [PATCH v4 07/13] Implement driver interface domainGetMemoryParamters for QEmu

On Tue, 12 Oct 2010 17:51:54 +0200, Daniel Veillard <veillard(a)redhat.com&gt; wrote: > On Fri, Oct 08, 2010 at 05:45:55PM +0530, Nikunj A. Dadhania wrote: > > From: Nikunj A. Dadhania <nikunj(a)linux.vnet.ibm.com&gt; > > > > V4: > > * prototype change: add unsigned int flags > > > > Driver interface for getting memory parameters, eg. hard_limit, soft_limit and > > swap_hard_limit. > > + qemuReportError(VIR_ERR_INVALID_ARG, > > + "%s", _("Invalid parameter count")); > > + goto cleanup; > > + } > > okay, this mean the application must always call with 0 first to get > the exact value or this will break, fine but probably need to be made > more clear from the description in libvirt.c .... TODO > Sure, I will take care of updating the api desc in libvirt.c, I haven't used word always there. > > + if (virCgroupForDomain(driver->cgroup, vm->def->name, &group, 0) != 0) { > > + qemuReportError(VIR_ERR_INTERNAL_ERROR, > > + _("cannot find cgroup for domain %s"), vm->def->name); > > + goto cleanup; > > + } > > + > > + for (i = 0; i < *nparams; i++) { > > + virMemoryParameterPtr param = &params[i]; > > + val = 0; > > + param->value.ul = 0; > > + param->type = VIR_DOMAIN_MEMORY_FIELD_ULLONG; > > + > > + switch(i) { > > + case 0: /* fill memory hard limit here */ > > + rc = virCgroupGetMemoryHardLimit(group, &val); > > + if (rc != 0) { > > + virReportSystemError(-rc, "%s", > > + _("unable to get memory hard limit")); > > + continue; > > + } > > + if (virStrcpyStatic(param->field, VIR_DOMAIN_MEMORY_HARD_LIMIT) == NULL) { > > + qemuReportError(VIR_ERR_INTERNAL_ERROR, > > + "%s", _("Field memory hard limit too long for destination")); > > + continue; > > + } > > + param->value.ul = val; > > + break; > > + > > + case 1: /* fill memory soft limit here */ > > + rc = virCgroupGetMemorySoftLimit(group, &val); > > + if (rc != 0) { > > + virReportSystemError(-rc, "%s", > > + _("unable to get memory soft limit")); > > + continue; > > + } > > + if (virStrcpyStatic(param->field, VIR_DOMAIN_MEMORY_SOFT_LIMIT) == NULL) { > > + qemuReportError(VIR_ERR_INTERNAL_ERROR, > > + "%s", _("Field memory soft limit too long for destination")); > > + continue; > > + } > > + param->value.ul = val; > > + break; > > + > > + case 2: /* fill swap hard limit here */ > > + rc = virCgroupGetSwapHardLimit(group, &val); > > + if (rc != 0) { > > + virReportSystemError(-rc, "%s", > > + _("unable to get swap hard limit")); > > + continue; > > + } > > + if (virStrcpyStatic(param->field, VIR_DOMAIN_SWAP_HARD_LIMIT) == NULL) { > > + qemuReportError(VIR_ERR_INTERNAL_ERROR, > > + "%s", _("Field swap hard limit too long for destination")); > > + continue; > > + } > > + param->value.ul = val; > > + break; > > + > > + default: > > + break; > > + /* should not hit here */ > > + } > > + } > > Okay, I'm not sure we actually need a loop here, but it may help > refactoring... I guess this is related to my previous thinking, if nparams < QEMU_NB_MEM_PARAM, fill only till nparams and return. But with the change of the logic, I think loop may not be required now.

> I'm still having a problem with the code ignoring any error occuring in > the loop, and fixing this in the same way. If there is an error the > application *must* learn about it instead of trusting uninitialized > memory as being data ! > Maybe a memset is in order actually before entering that loop to avoid > edge case problems... TODO too > By TODO you mean the error handling, right?

I am taking care of setting the values to zero currently, and it does not tell the application whether to use this value or not. One option could be adding VIR_DOMAIN_MEMORY_INVALID in virMemoryParameterType and setting it in the beginning of the loop. Comments?