Re: [PATCH v4] mm: introduce validity check on vm dirtiness settings

[Yafang Shao <laoar.shao@gmail.com>]

Got it.
I will submit a new patch then.

Thanks
Yafang

2017-09-28 3:33 GMT+08:00 Andrew Morton <akpm@linux-foundation.org>:
> On Wed, 27 Sep 2017 12:14:10 +0800 Yafang Shao <laoar.shao@gmail.com> wrote:
>
>> 2017-09-27 10:54 GMT+08:00 Andrew Morton <akpm@linux-foundation.org>:
>> > On Wed, 27 Sep 2017 09:38:21 +0800 Yafang Shao <laoar.shao@gmail.com> wrote:
>> >
>> >> > And existing scripts which do not do this will cease to work correctly,
>> >> > no?
>> >> >
>> >>
>> >> The existing scritpts won't work correctly. That's also what I have
>> >> worried before.
>> >>
>> >> But under this condition, there's a error message generated by "sysctl
>> >> -w" to tell them the first setting was failure.
>> >> This error message may be a reminder to them that there are some
>> >> connections between background and direct limit, and should not set
>> >> arbitrary.
>> >> May that's better. I'm not sure.
>> >
>> > Maybe we can leave the logic as-is and simply print a warning when an
>> > illogical state exists.
>> >
>>
>> You mean, just modified the  code as bellow ?
>> in function  domain_dirty_limits()
>> -        if (bg_thresh >= thresh)
>> +     if (bg_thresh >= thresh) {
>> +        pr_warn("vm direct limit should greater than background limit.\n");
>>           bg_thresh = thresh / 2;
>> +     }
>
> Something like that.
>
>> will this generate lots of log ?
>
> Well, it's one message per write to a procfs file, when that write
> causes an errant state.  Sounds manageable?  It would be nice if we
> could somehow help the operator to figure out that writing in a
> different order will prevent the incorrect state (and hence the
> warning).
>

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