Re: [PATCH 13/13] libnvdimm, namespace: Publish page structure init state / control

[Dan Williams]

On Thu, Jul 5, 2018 at 12:49 PM, Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> On Thu, Jul 05, 2018 at 07:46:05AM -0700, Dan Williams wrote:
>> On Thu, Jul 5, 2018 at 1:29 AM, Johannes Thumshirn <jthumshirn@xxxxxxx> wrote:
>> > On Wed, Jul 04, 2018 at 11:50:13PM -0700, Dan Williams wrote:
>> >> +static ssize_t memmap_state_store(struct device *dev,
>> >> +             struct device_attribute *attr, const char *buf, size_t len)
>> >> +{
>> >> +     int i;
>> >> +     struct nd_pfn *nd_pfn = to_nd_pfn_safe(dev);
>> >> +     struct memmap_async_state *async = &nd_pfn->async;
>> >> +
>> >> +     if (strcmp(buf, "sync") == 0)
>> >> +             /* pass */;
>> >> +     else if (strcmp(buf, "sync\n") == 0)
>> >> +             /* pass */;
>> >> +     else
>> >> +             return -EINVAL;
>> >
>> > Hmm what about:
>> >
>> >         if (strncmp(buf, "sync", 4))
>> >            return -EINVAL;
>> >
>> > This collapses 6 lines into 4.
>>
>> ...but that also allows 'echo "syncAndThenSomeGarbage" >
>> /sys/.../memmap_state' to succeed.
>
>         if (strncmp(buf, "sync", 4))
>                 return -EINVAL;
>         if (buf[4] != '\0' && buf[4] != '\n')
>                 return -EINVAL;
>

Not sure that's a win either, I'd rather just:

+       if (strcmp(buf, "sync") == 0 || strcmp(buf, "sync\n") == 0)
+               /* pass */;
+       else
+               return -EINVAL;

If we're trying to save those 2 lines.