Re: [PATCH -next v2 2/9] blk-iocost: improve hanlder of match_u64()

[Yu Kuai]

Hi,

在 2022/12/01 18:08, Tejun Heo 写道:
> On Thu, Dec 01, 2022 at 10:15:53AM +0800, Yu Kuai wrote:
> > Hi,
> >
> > 在 2022/12/01 4:32, Tejun Heo 写道:
> > > On Wed, Nov 30, 2022 at 09:21:49PM +0800, Li Nan wrote:
> > > > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> > > >
> > > > 1) There are one place that return value of match_u64() is not checked.
> > > > 2) If match_u64() failed, return value is set to -EINVAL despite that
> > > >      there are other possible errnos.
> > >
> > > Ditto. Does this matter?
> >
> > It's not a big deal, but I think at least return value of match_u64()
> > should be checked, we don't want to continue with invalid input, right?
>
> Yeah, sure.
>
> > By the way, match_u64() can return -ERANGE, which can provide more
> > specific error messge to user.
>
> I'm really not convinced going over 64bit range would be all that difficult
> to spot whether the error code is -EINVAL or -ERANGE. There isn't anything
> wrong with returning -ERANGE but the fact that that particular function
> returns an error code doesn't necessarily mean that it *must* be forwarded.
>
> Imagine that we used sscanf(buf, "%llu", &value) to parse the number
> instead. We'd only know whether the parsing would have succeeded or not and
> would probably return -EINVAL on failure and the behavior would be just
> fine. This does not matter *at all*.
>
> So, idk, I'm not necessarily against it but changing -EINVAL to -ERANGE is
> pure churn. Nothing material is being improved by that change.

Thanks for the review and explanation, I'll just keep the addition of
return value  checking of the former 2 patches.

Thanks,
Kuai