Re: [PATCH v3 1/2] hw/nvme: fix incorrect use of errp/local_err

[Markus Armbruster]

Klaus Jensen <its@irrelevant.dk> writes:

> On Nov 11 07:55, Markus Armbruster wrote:
>> Klaus Jensen <its@irrelevant.dk> writes:
>> 
>> > On Nov 11 07:36, Markus Armbruster wrote:
>> >> Klaus Jensen <its@irrelevant.dk> writes:
>> >> 
>> >> > From: Klaus Jensen <k.jensen@samsung.com>
>> >> >
>> >> > Remove an unnecessary local Error value in nvme_realize(). In the
>> >> > process, change nvme_check_constraints() into returning a bool.
>> >> >
>> >> > Finally, removing the local Error value also fixes a bug where an error
>> >> > returned from nvme_init_subsys() would be lost.
>> >> 
>> >> Would it be lost?  It's the hunk below:
>> >> 
>> >> > Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> >> > Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
>> >> > ---
>> >> >  hw/nvme/ctrl.c | 48 +++++++++++++++++++++++-------------------------
>> >> >  1 file changed, 23 insertions(+), 25 deletions(-)
>> >> >
>> >> > diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
>> >> > index ac3885ce5079..a5c0a5fa6ce2 100644
>> >> > --- a/hw/nvme/ctrl.c
>> >> > +++ b/hw/nvme/ctrl.c
>> >> 
>> >> [...]
>> >> 
>> >> > @@ -7586,7 +7585,6 @@ static void nvme_realize(PCIDevice *pci_dev, 
>> >> > Error **errp)
>> >>    static void nvme_realize(PCIDevice *pci_dev, Error **errp)
>> >>    {
>> >>        NvmeCtrl *n = NVME(pci_dev);
>> >>        NvmeNamespace *ns;
>> >>        Error *local_err = NULL;
>> >> 
>> >> @local_err is null.
>> >> 
>> >>        NvmeCtrl *pn = NVME(pcie_sriov_get_pf(pci_dev));
>> >> 
>> >>        if (pci_is_vf(pci_dev)) {
>> >>            /*
>> >>             * VFs derive settings from the parent. PF's lifespan exceeds
>> >>             * that of VF's, so it's safe to share params.serial.
>> >>             */
>> >>            memcpy(&n->params, &pn->params, sizeof(NvmeParams));
>> >>            n->subsys = pn->subsys;
>> >>        }
>> >> 
>> >>        nvme_check_constraints(n, &local_err);
>> >>        if (local_err) {
>> >>            error_propagate(errp, local_err);
>> >>            return;
>> >>        }
>> >> 
>> >> @local_err still is null.
>> >> 
>> >>        qbus_init(&n->bus, sizeof(NvmeBus), TYPE_NVME_BUS,
>> >> >                &pci_dev->qdev, n->parent_obj.qdev.id);
>> >> >  
>> >> >      if (nvme_init_subsys(n, errp)) {
>> >> > -        error_propagate(errp, local_err);
>> >> 
>> >> Since @local_err is null, this error_propagate() does nothing.  The
>> >> error from nvme_init_subsys() remains in @errp.
>> >> 
>> >
>> > Oh, right. Thanks.
>> >
>> > I misread the function documentation, getting the impression that it
>> > would overwrite dst_errp regardless of the value of local_err.
>> 
>> Happens :)
>> 
>> If you have suggestions on improving the doc, shoot.
>> 
>> This commit's message could perhaps be adjusted like
>> 
>>     hw/nvme: Clean up confused use of errp/local_err
>> 
>>     Remove an unnecessary local Error value in nvme_realize(). In the
>>     process, change nvme_check_constraints() to return a bool.
>> 
>> What do you think?
>
> Sounds good ;)

Reviewed-by: Markus Armbruster <armbru@redhat.com>