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

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

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;
+     }

will this generate lots of log ?

Thanks
Yafang

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