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

From: Yu Kuai
Date: Thu Dec 01 2022 - 08:47:49 EST


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