linux-kernel - Re: [PATCH 1/2] lib/strtox: introduce kstrtoull

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Message-ID: <15cf089f-be9a-4762-ae6b-4791efca6b44@gmx.com>
Date: Thu, 21 Dec 2023 07:08:08 +1030
From: Qu Wenruo <quwenruo.btrfs@....com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Qu Wenruo <wqu@...e.com>
Cc: Alexey Dobriyan <adobriyan@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>, linux-btrfs@...r.kernel.org,
 Christophe JAILLET <christophe.jaillet@...adoo.fr>,
 linux-kernel@...r.kernel.org, David Sterba <dsterba@...e.cz>
Subject: Re: [PATCH 1/2] lib/strtox: introduce kstrtoull_suffix() helper



On 2023/12/21 00:54, Andy Shevchenko wrote:
>
> On Wed, Dec 20, 2023 at 08:31:09PM +1030, Qu Wenruo wrote:
>> On 2023/12/20 20:24, Alexey Dobriyan wrote:
>>>> Just as mentioned in the comment of memparse(), the simple_stroull()
>>>> usage can lead to overflow all by itself.
>>>
>>> which is the root cause...
>>>
>>> I don't like one char suffixes. They are easy to integrate but then the
>>> _real_ suffixes are "MiB", "GiB", etc.
>>>
>>> If you care only about memparse(), then using _parse_integer() can be
>>> arranged. I don't see why not.
>>
>> Well, personally speaking I don't think we should even support the suffix at
>> all, at least for the only two usage inside btrfs.
>>
>> But unfortunately I'm not the one to do the final call, and the final call
>> is to keep the suffix behavior...
>>
>> And indeed using _parse_integer() with _parse_interger_fixup_radix() would
>> be better, as we don't need to extend the _kstrtoull() code base.
>
> My comment on the first patch got vanished due to my MTA issues, but I'll try
> to summarize my point here.
>
> First of all, I do not like the naming, it's too vague. What kind of suffix?
> Do we suppose to have suffix in the input? What will be the behaviour w/o
> suffix?  And so on...

I really like David Sterb to hear this though.

To me, we should mark memparse() as deprecated as soon as possible, not
spreading the damn pandemic to any newer code.

The "convenience" is not an excuse to use incorrect code.

>
> Second, if it's a problem in memparse(), just fix it and that's all.

Nope, the memparse() itself doesn't have any way to indicate errors.

It's not fixable in the first place, as long as you want a drop-in solution.

>
> Third, as Alexey said, we have metric and byte suffixes and they are different.
> Supporting one without the other is just adding to the existing confusion.
>
> Last, but not least, we do NOT accept new code in the lib/ without test cases.
>
> So, that said here is my formal NAK for this series (at least in this form).

Then why there is the hell of memparse() in the first place?
It doesn't have test case (we have cmdline_kunit, but it doesn't test
memparse() at all), nor the proper error detection.

I'm fine to get my patch rejected, but why the hell of memparse() is
here in the first place?
It doesn't fit any of the standard you mentioned.

Thanks,
Qu

>
> P.S> The Subject should start with either kstrtox: or lib/kstrtox.c.
>